<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:8b8ec977-4d04-4764-a4a3-617510e4e559,g:398e60f3-b943-456d-a95a-f01d762fe83a-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef roleURI="http://www.magnite.com/role/CondensedConsolidatedBalanceSheets" xlink:type="simple" xlink:href="mgni-20220331.xsd#CondensedConsolidatedBalanceSheets"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/CondensedConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_ef6618c9-c647-4fb7-8816-3ac71f3f5327" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Assets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_118a56f6-99d9-401c-88ca-7a5d19603912" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_ef6618c9-c647-4fb7-8816-3ac71f3f5327" xlink:to="loc_us-gaap_AssetsCurrent_118a56f6-99d9-401c-88ca-7a5d19603912" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_18d49d46-9e0b-4ca1-a41c-32d6d94f64da" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_ef6618c9-c647-4fb7-8816-3ac71f3f5327" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_18d49d46-9e0b-4ca1-a41c-32d6d94f64da" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_88d8f41f-a96a-4181-ac90-63a04f196f36" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_ef6618c9-c647-4fb7-8816-3ac71f3f5327" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_88d8f41f-a96a-4181-ac90-63a04f196f36" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_InternalUseSoftwareDevelopmentCostsNet_707a1416-b8a6-43f1-b964-e10b09378795" xlink:href="mgni-20220331.xsd#mgni_InternalUseSoftwareDevelopmentCostsNet"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_ef6618c9-c647-4fb7-8816-3ac71f3f5327" xlink:to="loc_mgni_InternalUseSoftwareDevelopmentCostsNet_707a1416-b8a6-43f1-b964-e10b09378795" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_7c4468ce-a2c9-4719-9f5f-a3df6d126c86" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_ef6618c9-c647-4fb7-8816-3ac71f3f5327" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_7c4468ce-a2c9-4719-9f5f-a3df6d126c86" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_67f46682-a39b-4bba-834f-e6c6402f49ac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_ef6618c9-c647-4fb7-8816-3ac71f3f5327" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_67f46682-a39b-4bba-834f-e6c6402f49ac" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_10046749-33a3-43f7-a14d-756deb01c3b3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Goodwill"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_ef6618c9-c647-4fb7-8816-3ac71f3f5327" xlink:to="loc_us-gaap_Goodwill_10046749-33a3-43f7-a14d-756deb01c3b3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_fd57ba97-d3f7-49d4-a966-5e23c90d4280" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_56f64320-fe0e-4a58-88ea-3cb089a40c06" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_fd57ba97-d3f7-49d4-a966-5e23c90d4280" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_56f64320-fe0e-4a58-88ea-3cb089a40c06" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_99aa950c-a9e2-4477-a8cf-e8f8f04712cc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_fd57ba97-d3f7-49d4-a966-5e23c90d4280" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_99aa950c-a9e2-4477-a8cf-e8f8f04712cc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_95d98af7-a00c-40f0-a9df-e75b0aa22e08" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_fd57ba97-d3f7-49d4-a966-5e23c90d4280" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_95d98af7-a00c-40f0-a9df-e75b0aa22e08" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_5f9c5648-422e-4459-a182-06520cbd1df7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_4346428e-b15b-468f-91fc-4a5d7a5a8c7a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Liabilities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_5f9c5648-422e-4459-a182-06520cbd1df7" xlink:to="loc_us-gaap_Liabilities_4346428e-b15b-468f-91fc-4a5d7a5a8c7a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_b1673aa0-aa5b-4e47-b7c5-b5ef70b57b44" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_5f9c5648-422e-4459-a182-06520cbd1df7" xlink:to="loc_us-gaap_CommitmentsAndContingencies_b1673aa0-aa5b-4e47-b7c5-b5ef70b57b44" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_1634adc5-7350-49b9-906c-201780829d4d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_5f9c5648-422e-4459-a182-06520cbd1df7" xlink:to="loc_us-gaap_StockholdersEquity_1634adc5-7350-49b9-906c-201780829d4d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_5712beff-3b04-4f6d-853a-dfd20aad1003" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Liabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_bdf0521d-b782-4374-a477-2b79dcf3c9fa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_5712beff-3b04-4f6d-853a-dfd20aad1003" xlink:to="loc_us-gaap_LiabilitiesCurrent_bdf0521d-b782-4374-a477-2b79dcf3c9fa" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_8de96f3f-64b4-4a5e-bf59-0db0cf904eaf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_5712beff-3b04-4f6d-853a-dfd20aad1003" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_8de96f3f-64b4-4a5e-bf59-0db0cf904eaf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_9a3a6d13-b8c3-46cf-b9ed-bbeec6bbbc7d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_5712beff-3b04-4f6d-853a-dfd20aad1003" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_9a3a6d13-b8c3-46cf-b9ed-bbeec6bbbc7d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_61fd1ef4-c566-4d22-a0bc-c906ecba7c8a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_5712beff-3b04-4f6d-853a-dfd20aad1003" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_61fd1ef4-c566-4d22-a0bc-c906ecba7c8a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_b3e83de7-def0-49d6-90ba-90a03cabc8f3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_5712beff-3b04-4f6d-853a-dfd20aad1003" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_b3e83de7-def0-49d6-90ba-90a03cabc8f3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_6e0d3054-80bf-4efc-a437-e41ed2636793" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_bc043a4f-d12d-4c78-9c66-a08384788ebf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_6e0d3054-80bf-4efc-a437-e41ed2636793" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_bc043a4f-d12d-4c78-9c66-a08384788ebf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_14f3168c-5aab-43d6-9d01-f0332c70a6b5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_6e0d3054-80bf-4efc-a437-e41ed2636793" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_14f3168c-5aab-43d6-9d01-f0332c70a6b5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtCurrent_f69faeb1-9516-4473-9c0d-05b39f67fff8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_6e0d3054-80bf-4efc-a437-e41ed2636793" xlink:to="loc_us-gaap_DebtCurrent_f69faeb1-9516-4473-9c0d-05b39f67fff8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesCurrent_e61e0ac6-c780-4e76-b5a1-b70fdfc39fd3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherLiabilitiesCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_6e0d3054-80bf-4efc-a437-e41ed2636793" xlink:to="loc_us-gaap_OtherLiabilitiesCurrent_e61e0ac6-c780-4e76-b5a1-b70fdfc39fd3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_c1c4c997-d697-4603-8bab-afe66a8cdca7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_71af5dfe-6d08-4ca8-a914-6a74187707d6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_c1c4c997-d697-4603-8bab-afe66a8cdca7" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_71af5dfe-6d08-4ca8-a914-6a74187707d6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_92e25cdc-8b57-49c4-aece-bd6045401026" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_c1c4c997-d697-4603-8bab-afe66a8cdca7" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_92e25cdc-8b57-49c4-aece-bd6045401026" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_c451ce19-39b4-44b1-87fa-03d578fac998" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PreferredStockValue"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_c1c4c997-d697-4603-8bab-afe66a8cdca7" xlink:to="loc_us-gaap_PreferredStockValue_c451ce19-39b4-44b1-87fa-03d578fac998" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_f1f84530-c97e-45a3-ba6e-f2f4501e9ce2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_c1c4c997-d697-4603-8bab-afe66a8cdca7" xlink:to="loc_us-gaap_AdditionalPaidInCapital_f1f84530-c97e-45a3-ba6e-f2f4501e9ce2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_7406ac02-f2b1-4317-bb71-381f62a1da06" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockValue"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_c1c4c997-d697-4603-8bab-afe66a8cdca7" xlink:to="loc_us-gaap_CommonStockValue_7406ac02-f2b1-4317-bb71-381f62a1da06" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValue_71387609-a7d6-4b94-9365-9802fd06f422" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TreasuryStockValue"/>
    <link:calculationArc order="6" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_c1c4c997-d697-4603-8bab-afe66a8cdca7" xlink:to="loc_us-gaap_TreasuryStockValue_71387609-a7d6-4b94-9365-9802fd06f422" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/CondensedConsolidatedStatementsofOperations" xlink:type="simple" xlink:href="mgni-20220331.xsd#CondensedConsolidatedStatementsofOperations"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/CondensedConsolidatedStatementsofOperations" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_54019789-b41a-4b85-9af8-69eb9513aba7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_a9b09732-bc99-4e4c-a4fd-c92e71d0fa04" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_54019789-b41a-4b85-9af8-69eb9513aba7" xlink:to="loc_us-gaap_OperatingIncomeLoss_a9b09732-bc99-4e4c-a4fd-c92e71d0fa04" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_8c2eee34-7472-40d2-b2ad-cff028911329" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_54019789-b41a-4b85-9af8-69eb9513aba7" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_8c2eee34-7472-40d2-b2ad-cff028911329" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_9e494a18-e28b-4f4d-8f1b-fe8af1d9acca" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_0937e7f0-2250-4719-95ee-8e25c00e524c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_9e494a18-e28b-4f4d-8f1b-fe8af1d9acca" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_0937e7f0-2250-4719-95ee-8e25c00e524c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_b39dd15f-0226-47f1-957b-e66cdb2ebd6d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_9e494a18-e28b-4f4d-8f1b-fe8af1d9acca" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_b39dd15f-0226-47f1-957b-e66cdb2ebd6d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_e5bfe30c-0e8e-4590-b268-81c1adf672b0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNet_6d34cf85-62d6-481e-ae9c-aa3c88e591a7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestIncomeExpenseNet"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NonoperatingIncomeExpense_e5bfe30c-0e8e-4590-b268-81c1adf672b0" xlink:to="loc_us-gaap_InterestIncomeExpenseNet_6d34cf85-62d6-481e-ae9c-aa3c88e591a7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherOperatingIncome_49d22c07-59ee-4d44-b570-46cfe658bd23" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherOperatingIncome"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NonoperatingIncomeExpense_e5bfe30c-0e8e-4590-b268-81c1adf672b0" xlink:to="loc_us-gaap_OtherOperatingIncome_49d22c07-59ee-4d44-b570-46cfe658bd23" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_b191d1be-82ef-49c5-9fd9-78edb3c0f3a5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NonoperatingIncomeExpense_e5bfe30c-0e8e-4590-b268-81c1adf672b0" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_b191d1be-82ef-49c5-9fd9-78edb3c0f3a5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_a98e7566-348f-41e9-a69c-3c6fcc980b0b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CostsAndExpenses"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpense_2e6a973a-dba6-4c02-9e03-d2691147b22e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SellingAndMarketingExpense"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_a98e7566-348f-41e9-a69c-3c6fcc980b0b" xlink:to="loc_us-gaap_SellingAndMarketingExpense_2e6a973a-dba6-4c02-9e03-d2691147b22e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_RestructuringChargesAndBusinessCombinationAcquisitionRelatedCosts_7d831e95-0f11-494f-b728-587a166063d3" xlink:href="mgni-20220331.xsd#mgni_RestructuringChargesAndBusinessCombinationAcquisitionRelatedCosts"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_a98e7566-348f-41e9-a69c-3c6fcc980b0b" xlink:to="loc_mgni_RestructuringChargesAndBusinessCombinationAcquisitionRelatedCosts_7d831e95-0f11-494f-b728-587a166063d3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_c8757ce4-bcee-4c07-b7c2-902efe8a4eff" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CostOfRevenue"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_a98e7566-348f-41e9-a69c-3c6fcc980b0b" xlink:to="loc_us-gaap_CostOfRevenue_c8757ce4-bcee-4c07-b7c2-902efe8a4eff" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_0777f17c-6027-41b6-834b-65e3d3744943" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_a98e7566-348f-41e9-a69c-3c6fcc980b0b" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_0777f17c-6027-41b6-834b-65e3d3744943" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_41f687ed-35b1-46ae-8b86-3a4182e4a115" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_a98e7566-348f-41e9-a69c-3c6fcc980b0b" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_41f687ed-35b1-46ae-8b86-3a4182e4a115" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_d3a6c821-08bc-493d-b0a7-78266dc56df8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_b907d95f-c170-4c7c-b3de-931d087d389d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingIncomeLoss_d3a6c821-08bc-493d-b0a7-78266dc56df8" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_b907d95f-c170-4c7c-b3de-931d087d389d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_f6a517bd-c94e-4142-80fb-a10d3908f026" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CostsAndExpenses"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingIncomeLoss_d3a6c821-08bc-493d-b0a7-78266dc56df8" xlink:to="loc_us-gaap_CostsAndExpenses_f6a517bd-c94e-4142-80fb-a10d3908f026" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/CondensedConsolidatedStatementsofComprehensiveIncomeLoss" xlink:type="simple" xlink:href="mgni-20220331.xsd#CondensedConsolidatedStatementsofComprehensiveIncomeLoss"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/CondensedConsolidatedStatementsofComprehensiveIncomeLoss" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_3bdf20c5-67e1-4351-b4c8-862a0de918ce" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_23fb4975-8f2d-4510-ae35-906bb0618474" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_3bdf20c5-67e1-4351-b4c8-862a0de918ce" xlink:to="loc_us-gaap_NetIncomeLoss_23fb4975-8f2d-4510-ae35-906bb0618474" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_5ff377d0-6ee1-4fba-9719-5ceb3cf878c5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_3bdf20c5-67e1-4351-b4c8-862a0de918ce" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_5ff377d0-6ee1-4fba-9719-5ceb3cf878c5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_a5dd70b0-d8e3-4f97-acb0-91edb5e670b4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent_968a2839-d72f-42f3-a8db-27df9a060121" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_a5dd70b0-d8e3-4f97-acb0-91edb5e670b4" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent_968a2839-d72f-42f3-a8db-27df9a060121" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/CondensedConsolidatedStatementsofCashFlows" xlink:type="simple" xlink:href="mgni-20220331.xsd#CondensedConsolidatedStatementsofCashFlows"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/CondensedConsolidatedStatementsofCashFlows" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_69ca75f7-2e1d-40cc-8e01-0306e4c500de" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_84027753-3602-4e85-9b8d-f0761cd41fc1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_69ca75f7-2e1d-40cc-8e01-0306e4c500de" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_84027753-3602-4e85-9b8d-f0761cd41fc1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_0def1086-47a2-4adf-b749-a4d5bfb293a8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_69ca75f7-2e1d-40cc-8e01-0306e4c500de" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_0def1086-47a2-4adf-b749-a4d5bfb293a8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_0c9b9596-0011-41d6-b0f0-dccce0397044" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_69ca75f7-2e1d-40cc-8e01-0306e4c500de" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_0c9b9596-0011-41d6-b0f0-dccce0397044" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_58ef1c4f-629e-43e4-bb04-12b25085a988" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_69ca75f7-2e1d-40cc-8e01-0306e4c500de" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_58ef1c4f-629e-43e4-bb04-12b25085a988" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_4ca3ff47-e2ab-4411-9aa1-8454feb88350" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_4ca3ff47-e2ab-4411-9aa1-8454feb88350" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_b8d22d10-6cdb-46c5-af06-6151b42ef918" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_b8d22d10-6cdb-46c5-af06-6151b42ef918" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_e468c7c9-fcdf-4722-b220-53f50ef225c7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_e468c7c9-fcdf-4722-b220-53f50ef225c7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_37cceb81-64c2-4f7a-bdc7-3875472cf6f1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensation"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:to="loc_us-gaap_ShareBasedCompensation_37cceb81-64c2-4f7a-bdc7-3875472cf6f1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxesAndTaxCredits_f9b7681e-abe5-4028-a1df-a6d50bcc3bd4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredIncomeTaxesAndTaxCredits"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:to="loc_us-gaap_DeferredIncomeTaxesAndTaxCredits_f9b7681e-abe5-4028-a1df-a6d50bcc3bd4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForDoubtfulAccounts_9f381e2c-6b65-4681-9a26-92efc8c87660" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProvisionForDoubtfulAccounts"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:to="loc_us-gaap_ProvisionForDoubtfulAccounts_9f381e2c-6b65-4681-9a26-92efc8c87660" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossUnrealized_cbf1737c-6088-49cc-8a22-9695bdbab6ee" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignCurrencyTransactionGainLossUnrealized"/>
    <link:calculationArc order="7" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossUnrealized_cbf1737c-6088-49cc-8a22-9695bdbab6ee" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_06455948-4dc8-4b2c-8ee2-994a78c0d5e8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_06455948-4dc8-4b2c-8ee2-994a78c0d5e8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_9439de1c-b078-473c-950f-94b6687f5fda" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:calculationArc order="9" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:to="loc_us-gaap_NetIncomeLoss_9439de1c-b078-473c-950f-94b6687f5fda" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_72c80ed4-6f42-43b4-aecf-bd1c0c640ec3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
    <link:calculationArc order="10" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_72c80ed4-6f42-43b4-aecf-bd1c0c640ec3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_50708bfa-5d1f-4d0f-93f2-da93ab507c25" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:calculationArc order="11" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_50708bfa-5d1f-4d0f-93f2-da93ab507c25" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_7bb77f79-fca2-4797-bc3a-ff8c76eef247" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:calculationArc order="12" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_7bb77f79-fca2-4797-bc3a-ff8c76eef247" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_NonCashLeaseExpense_4f5021f1-23c8-4a1c-aee5-0a8c1a15f9fd" xlink:href="mgni-20220331.xsd#mgni_NonCashLeaseExpense"/>
    <link:calculationArc order="13" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:to="loc_mgni_NonCashLeaseExpense_4f5021f1-23c8-4a1c-aee5-0a8c1a15f9fd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfIntangibleAssetsFinitelived_8ecd18d4-5031-4f0a-b4da-eb0ddbad11fb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ImpairmentOfIntangibleAssetsFinitelived"/>
    <link:calculationArc order="14" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1a986f76-2205-4e02-9812-70d14a35efe5" xlink:to="loc_us-gaap_ImpairmentOfIntangibleAssetsFinitelived_8ecd18d4-5031-4f0a-b4da-eb0ddbad11fb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_11b97186-b992-4725-b449-85b5b9571eef" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_ffabbc45-0e49-4e78-84f9-c8d58ba69d8a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_11b97186-b992-4725-b449-85b5b9571eef" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_ffabbc45-0e49-4e78-84f9-c8d58ba69d8a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_26029214-7363-4d57-990c-751689604263" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_11b97186-b992-4725-b449-85b5b9571eef" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_26029214-7363-4d57-990c-751689604263" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToDevelopSoftware_08a6a2a0-102d-4b12-90a6-bd4eca0d33c7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToDevelopSoftware"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_11b97186-b992-4725-b449-85b5b9571eef" xlink:to="loc_us-gaap_PaymentsToDevelopSoftware_08a6a2a0-102d-4b12-90a6-bd4eca0d33c7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_e7544aad-9942-42db-a48d-06864af44e91" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_259f5f52-e7a8-4c84-9169-d6ba9e570599" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_e7544aad-9942-42db-a48d-06864af44e91" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_259f5f52-e7a8-4c84-9169-d6ba9e570599" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashNoncurrent_28fb50c2-5538-43f1-bd01-d9709e3e4bef" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedCashNoncurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_e7544aad-9942-42db-a48d-06864af44e91" xlink:to="loc_us-gaap_RestrictedCashNoncurrent_28fb50c2-5538-43f1-bd01-d9709e3e4bef" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashCurrent_9e3ca637-2c60-4ba9-a617-b8bf6f9b1b86" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedCashCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_e7544aad-9942-42db-a48d-06864af44e91" xlink:to="loc_us-gaap_RestrictedCashCurrent_9e3ca637-2c60-4ba9-a617-b8bf6f9b1b86" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_323331eb-f07b-41e9-abac-2a4d5b31f50e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_b10ac7b2-e269-4e61-baf0-260b6f36daf2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_323331eb-f07b-41e9-abac-2a4d5b31f50e" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_b10ac7b2-e269-4e61-baf0-260b6f36daf2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeasePrincipalPayments_79914881-70c0-4046-95aa-7bb091eaa59d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FinanceLeasePrincipalPayments"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_323331eb-f07b-41e9-abac-2a4d5b31f50e" xlink:to="loc_us-gaap_FinanceLeasePrincipalPayments_79914881-70c0-4046-95aa-7bb091eaa59d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_f0ce5a09-c928-4639-99a1-1e19c62cd1a5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_323331eb-f07b-41e9-abac-2a4d5b31f50e" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_f0ce5a09-c928-4639-99a1-1e19c62cd1a5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfDebt_34696535-e783-42ab-aeef-5b6d5efce0b9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RepaymentsOfDebt"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_323331eb-f07b-41e9-abac-2a4d5b31f50e" xlink:to="loc_us-gaap_RepaymentsOfDebt_34696535-e783-42ab-aeef-5b6d5efce0b9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_71e3dc79-1d77-4a28-95e6-6efab3006e2f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_323331eb-f07b-41e9-abac-2a4d5b31f50e" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_71e3dc79-1d77-4a28-95e6-6efab3006e2f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_6167a090-daa8-4620-bfac-8cb51af7f0dc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromStockOptionsExercised"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_323331eb-f07b-41e9-abac-2a4d5b31f50e" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_6167a090-daa8-4620-bfac-8cb51af7f0dc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_PaymentsForCappedCallOptions_98a2dce6-988e-4cd5-8461-99d3cda7d01b" xlink:href="mgni-20220331.xsd#mgni_PaymentsForCappedCallOptions"/>
    <link:calculationArc order="7" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_323331eb-f07b-41e9-abac-2a4d5b31f50e" xlink:to="loc_mgni_PaymentsForCappedCallOptions_98a2dce6-988e-4cd5-8461-99d3cda7d01b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromConvertibleDebt_88989052-13c9-4875-b835-69643bbbf3a6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromConvertibleDebt"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_323331eb-f07b-41e9-abac-2a4d5b31f50e" xlink:to="loc_us-gaap_ProceedsFromConvertibleDebt_88989052-13c9-4875-b835-69643bbbf3a6" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/OtherBalanceSheetAmountsAccountsPayableandAccruedExpensesDetails" xlink:type="simple" xlink:href="mgni-20220331.xsd#OtherBalanceSheetAmountsAccountsPayableandAccruedExpensesDetails"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/OtherBalanceSheetAmountsAccountsPayableandAccruedExpensesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_c15a0b1a-bc22-44b9-b746-a73bbd9b55b3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_AccountsPayableSellerCurrent_b9890524-2d28-405b-8299-8ba087786d41" xlink:href="mgni-20220331.xsd#mgni_AccountsPayableSellerCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_c15a0b1a-bc22-44b9-b746-a73bbd9b55b3" xlink:to="loc_mgni_AccountsPayableSellerCurrent_b9890524-2d28-405b-8299-8ba087786d41" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableTradeCurrent_0b42e1b1-5da5-4540-8165-dbb22c7f8fa2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountsPayableTradeCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_c15a0b1a-bc22-44b9-b746-a73bbd9b55b3" xlink:to="loc_us-gaap_AccountsPayableTradeCurrent_0b42e1b1-5da5-4540-8165-dbb22c7f8fa2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_d535ff8d-3aaf-409a-8e21-fc2fe3fb78c1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_c15a0b1a-bc22-44b9-b746-a73bbd9b55b3" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_d535ff8d-3aaf-409a-8e21-fc2fe3fb78c1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_IndemnificationClaimAccrualCurrent_7638151c-9a5d-4d5d-9507-554bf3ad9d36" xlink:href="mgni-20220331.xsd#mgni_IndemnificationClaimAccrualCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_c15a0b1a-bc22-44b9-b746-a73bbd9b55b3" xlink:to="loc_mgni_IndemnificationClaimAccrualCurrent_7638151c-9a5d-4d5d-9507-554bf3ad9d36" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/GoodwillIntangibleAssetsandCapitalizedCostsIncurredinCloudComputingArrangementsFiniteLivedIntangibleAssetsDetails" xlink:type="simple" xlink:href="mgni-20220331.xsd#GoodwillIntangibleAssetsandCapitalizedCostsIncurredinCloudComputingArrangementsFiniteLivedIntangibleAssetsDetails"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/GoodwillIntangibleAssetsandCapitalizedCostsIncurredinCloudComputingArrangementsFiniteLivedIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_e32c6282-1133-4b99-bd0f-e2e346bfd548" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_3811746b-1710-4433-95e7-718ddef253c8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_e32c6282-1133-4b99-bd0f-e2e346bfd548" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_3811746b-1710-4433-95e7-718ddef253c8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_3c84978f-4926-4320-8a04-d419610c1bf2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_e32c6282-1133-4b99-bd0f-e2e346bfd548" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_3c84978f-4926-4320-8a04-d419610c1bf2" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/GoodwillIntangibleAssetsandCapitalizedCostsIncurredinCloudComputingArrangementsFiniteLivedIntangibleAssetsFutureAmortizationExpenseDetails" xlink:type="simple" xlink:href="mgni-20220331.xsd#GoodwillIntangibleAssetsandCapitalizedCostsIncurredinCloudComputingArrangementsFiniteLivedIntangibleAssetsFutureAmortizationExpenseDetails"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/GoodwillIntangibleAssetsandCapitalizedCostsIncurredinCloudComputingArrangementsFiniteLivedIntangibleAssetsFutureAmortizationExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_fefc10b3-1707-46c4-9289-e1a694c841fb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_26f394b2-9427-4b4b-a72e-768ec4ee3ee8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_fefc10b3-1707-46c4-9289-e1a694c841fb" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_26f394b2-9427-4b4b-a72e-768ec4ee3ee8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_2e506e1c-c3e1-4942-8c40-56343cfdb0df" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_fefc10b3-1707-46c4-9289-e1a694c841fb" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_2e506e1c-c3e1-4942-8c40-56343cfdb0df" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_6858b4fd-bc00-44db-933d-f0f154ca7a50" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_fefc10b3-1707-46c4-9289-e1a694c841fb" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_6858b4fd-bc00-44db-933d-f0f154ca7a50" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_01f7ee94-182f-4807-bf7e-0b6d07d07572" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_fefc10b3-1707-46c4-9289-e1a694c841fb" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_01f7ee94-182f-4807-bf7e-0b6d07d07572" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_deac73c7-8d05-4f56-a87d-ecae1bc09a76" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_fefc10b3-1707-46c4-9289-e1a694c841fb" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_deac73c7-8d05-4f56-a87d-ecae1bc09a76" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour_57fd120c-7e87-4bca-a925-e83bd74c4af6" xlink:href="mgni-20220331.xsd#mgni_FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_fefc10b3-1707-46c4-9289-e1a694c841fb" xlink:to="loc_mgni_FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour_57fd120c-7e87-4bca-a925-e83bd74c4af6" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/BusinessCombinationsSpotXPurchaseConsiderationDetails" xlink:type="simple" xlink:href="mgni-20220331.xsd#BusinessCombinationsSpotXPurchaseConsiderationDetails"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/BusinessCombinationsSpotXPurchaseConsiderationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_6110b1a5-8dc9-4077-8fbe-ee59ce2f2a0e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_e8d553a0-5256-4923-b01c-ed9877905cdb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferred1_6110b1a5-8dc9-4077-8fbe-ee59ce2f2a0e" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_e8d553a0-5256-4923-b01c-ed9877905cdb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_f8c34452-f757-4576-a87d-927067c52182" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferred1_6110b1a5-8dc9-4077-8fbe-ee59ce2f2a0e" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_f8c34452-f757-4576-a87d-927067c52182" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_BusinessCombinationConsiderationTransferredWorkingCapitalAdjustments_2eb98b07-a427-4382-94b7-0a7c083917e7" xlink:href="mgni-20220331.xsd#mgni_BusinessCombinationConsiderationTransferredWorkingCapitalAdjustments"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferred1_6110b1a5-8dc9-4077-8fbe-ee59ce2f2a0e" xlink:to="loc_mgni_BusinessCombinationConsiderationTransferredWorkingCapitalAdjustments_2eb98b07-a427-4382-94b7-0a7c083917e7" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/BusinessCombinationsSpotXScheduleofRecognizedIdentifiedAssetsAcquiredandLiabilitiesAssumedDetails" xlink:type="simple" xlink:href="mgni-20220331.xsd#BusinessCombinationsSpotXScheduleofRecognizedIdentifiedAssetsAcquiredandLiabilitiesAssumedDetails"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/BusinessCombinationsSpotXScheduleofRecognizedIdentifiedAssetsAcquiredandLiabilitiesAssumedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill_f2318752-4055-4c47-9e5b-5d0c0ffbf269" xlink:href="mgni-20220331.xsd#mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_45813a9b-2185-4fd7-89c6-af57bb49f925" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill_f2318752-4055-4c47-9e5b-5d0c0ffbf269" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_45813a9b-2185-4fd7-89c6-af57bb49f925" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRestrictedCash_7f0231c2-5f75-49f3-bcf3-cfd00dfee2ca" xlink:href="mgni-20220331.xsd#mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRestrictedCash"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill_f2318752-4055-4c47-9e5b-5d0c0ffbf269" xlink:to="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRestrictedCash_7f0231c2-5f75-49f3-bcf3-cfd00dfee2ca" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsAccountsReceivables_bce819ff-ca31-4421-a3f2-5a28980e8a91" xlink:href="mgni-20220331.xsd#mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsAccountsReceivables"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill_f2318752-4055-4c47-9e5b-5d0c0ffbf269" xlink:to="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsAccountsReceivables_bce819ff-ca31-4421-a3f2-5a28980e8a91" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_86b10b6b-d354-43de-8846-9904a272729a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill_f2318752-4055-4c47-9e5b-5d0c0ffbf269" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_86b10b6b-d354-43de-8846-9904a272729a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_d6e19c6f-4a40-4f4d-8c02-c97d15f35c3e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill_f2318752-4055-4c47-9e5b-5d0c0ffbf269" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_d6e19c6f-4a40-4f4d-8c02-c97d15f35c3e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_983b549c-f674-4394-aeb4-81984f96f2ba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill_f2318752-4055-4c47-9e5b-5d0c0ffbf269" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_983b549c-f674-4394-aeb4-81984f96f2ba" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRightOfUseLeaseAsset_d748c60c-4b8c-42ef-8cf6-4c855289f343" xlink:href="mgni-20220331.xsd#mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRightOfUseLeaseAsset"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill_f2318752-4055-4c47-9e5b-5d0c0ffbf269" xlink:to="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRightOfUseLeaseAsset_d748c60c-4b8c-42ef-8cf6-4c855289f343" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_3ca66684-1044-4884-9dc3-058c080b5b3d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Goodwill"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill_f2318752-4055-4c47-9e5b-5d0c0ffbf269" xlink:to="loc_us-gaap_Goodwill_3ca66684-1044-4884-9dc3-058c080b5b3d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_7aa57089-8429-4a8d-a3e5-191ec44f7255" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccountsPayableAndAccruedLiabilities_1e9d4631-cac3-4f04-983c-1b3012568744" xlink:href="mgni-20220331.xsd#mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccountsPayableAndAccruedLiabilities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_7aa57089-8429-4a8d-a3e5-191ec44f7255" xlink:to="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccountsPayableAndAccruedLiabilities_1e9d4631-cac3-4f04-983c-1b3012568744" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_51344e54-6286-4278-9183-497ec325b46f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_7aa57089-8429-4a8d-a3e5-191ec44f7255" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_51344e54-6286-4278-9183-497ec325b46f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCapitalLeaseObligation_92e61a40-a62c-4d7f-933e-318604f5160c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCapitalLeaseObligation"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_7aa57089-8429-4a8d-a3e5-191ec44f7255" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCapitalLeaseObligation_92e61a40-a62c-4d7f-933e-318604f5160c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_9b9263bc-aaf8-4094-84fd-2243b4be2200" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_7aa57089-8429-4a8d-a3e5-191ec44f7255" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_9b9263bc-aaf8-4094-84fd-2243b4be2200" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_0d7bf874-1be5-46e1-847e-9ece1474b074" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill_f0116453-9c61-43af-a166-c4e2ce08efa8" xlink:href="mgni-20220331.xsd#mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_0d7bf874-1be5-46e1-847e-9ece1474b074" xlink:to="loc_mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill_f0116453-9c61-43af-a166-c4e2ce08efa8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_255a5bab-6c50-4e5a-be41-c9b1a0b906d8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_0d7bf874-1be5-46e1-847e-9ece1474b074" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_255a5bab-6c50-4e5a-be41-c9b1a0b906d8" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/BusinessCombinationsSpringServePurchaseConsiderationDetails" xlink:type="simple" xlink:href="mgni-20220331.xsd#BusinessCombinationsSpringServePurchaseConsiderationDetails"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/BusinessCombinationsSpringServePurchaseConsiderationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredIncludingEquityInterestInAcquireeHeldPriorToCombination1_b5cc4e2f-d887-49d9-a746-008973b125f8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredIncludingEquityInterestInAcquireeHeldPriorToCombination1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_fbbfc446-518f-4737-ba37-30b3be460528" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredIncludingEquityInterestInAcquireeHeldPriorToCombination1_b5cc4e2f-d887-49d9-a746-008973b125f8" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_fbbfc446-518f-4737-ba37-30b3be460528" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeFairValue1_22ecde5c-c557-46e6-9345-bacf8feed5fc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeFairValue1"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredIncludingEquityInterestInAcquireeHeldPriorToCombination1_b5cc4e2f-d887-49d9-a746-008973b125f8" xlink:to="loc_us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeFairValue1_22ecde5c-c557-46e6-9345-bacf8feed5fc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeRemeasurementGain_d549cd33-4fa5-497f-ad28-bb0ec1d9fd6c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeRemeasurementGain"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredIncludingEquityInterestInAcquireeHeldPriorToCombination1_b5cc4e2f-d887-49d9-a746-008973b125f8" xlink:to="loc_us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeRemeasurementGain_d549cd33-4fa5-497f-ad28-bb0ec1d9fd6c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_BusinessCombinationConsiderationTransferredIndemnificationClaimsHoldback_d9b5b529-4c38-4c03-9d5a-9604c1230b36" xlink:href="mgni-20220331.xsd#mgni_BusinessCombinationConsiderationTransferredIndemnificationClaimsHoldback"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredIncludingEquityInterestInAcquireeHeldPriorToCombination1_b5cc4e2f-d887-49d9-a746-008973b125f8" xlink:to="loc_mgni_BusinessCombinationConsiderationTransferredIndemnificationClaimsHoldback_d9b5b529-4c38-4c03-9d5a-9604c1230b36" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/MergerAcquisitionandRestructuringCostsMergerandRestructuringCostActivityDetails" xlink:type="simple" xlink:href="mgni-20220331.xsd#MergerAcquisitionandRestructuringCostsMergerandRestructuringCostActivityDetails"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/MergerAcquisitionandRestructuringCostsMergerandRestructuringCostActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_mgni_RestructuringChargesAndBusinessCombinationAcquisitionRelatedCosts_0ab0b887-6c48-417c-a202-70606c66fc74" xlink:href="mgni-20220331.xsd#mgni_RestructuringChargesAndBusinessCombinationAcquisitionRelatedCosts"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_4b069139-a4ad-4ccc-87ee-3e9e586c9a9c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_mgni_RestructuringChargesAndBusinessCombinationAcquisitionRelatedCosts_0ab0b887-6c48-417c-a202-70606c66fc74" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_4b069139-a4ad-4ccc-87ee-3e9e586c9a9c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_52ac5286-876e-43d6-85cc-a46966554f24" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestructuringCharges"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_mgni_RestructuringChargesAndBusinessCombinationAcquisitionRelatedCosts_0ab0b887-6c48-417c-a202-70606c66fc74" xlink:to="loc_us-gaap_RestructuringCharges_52ac5286-876e-43d6-85cc-a46966554f24" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_RestructuringReserveAndMergerRelatedCostsSettledWithoutCash_96511109-2feb-43f0-b263-05785dfac202" xlink:href="mgni-20220331.xsd#mgni_RestructuringReserveAndMergerRelatedCostsSettledWithoutCash"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_mgni_RestructuringChargesAndBusinessCombinationAcquisitionRelatedCosts_0ab0b887-6c48-417c-a202-70606c66fc74" xlink:to="loc_mgni_RestructuringReserveAndMergerRelatedCostsSettledWithoutCash_96511109-2feb-43f0-b263-05785dfac202" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_RestructuringImpairmentsSettledWithoutCash_e9e0ac03-b5bd-4a6a-bfa0-6177aaaceab7" xlink:href="mgni-20220331.xsd#mgni_RestructuringImpairmentsSettledWithoutCash"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_mgni_RestructuringChargesAndBusinessCombinationAcquisitionRelatedCosts_0ab0b887-6c48-417c-a202-70606c66fc74" xlink:to="loc_mgni_RestructuringImpairmentsSettledWithoutCash_e9e0ac03-b5bd-4a6a-bfa0-6177aaaceab7" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/LeaseObligationsScheduleofLeaseLiabilityMaturitiesDetails" xlink:type="simple" xlink:href="mgni-20220331.xsd#LeaseObligationsScheduleofLeaseLiabilityMaturitiesDetails"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/LeaseObligationsScheduleofLeaseLiabilityMaturitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_a96024ab-3d60-47e0-a2ba-a546b3221cb9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_fc2f9e3b-6415-47f7-8ea8-dccb63b09b35" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_a96024ab-3d60-47e0-a2ba-a546b3221cb9" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_fc2f9e3b-6415-47f7-8ea8-dccb63b09b35" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_90b09d26-b5ae-4bff-9da7-095fefe8667b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_a96024ab-3d60-47e0-a2ba-a546b3221cb9" xlink:to="loc_us-gaap_OperatingLeaseLiability_90b09d26-b5ae-4bff-9da7-095fefe8667b" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/LeaseObligationsScheduleofLeaseLiabilityMaturitiesDetails_1" xlink:type="simple" xlink:href="mgni-20220331.xsd#LeaseObligationsScheduleofLeaseLiabilityMaturitiesDetails_1"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/LeaseObligationsScheduleofLeaseLiabilityMaturitiesDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_67d10864-2a60-4353-b195-fd3e7aa0c8bf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_19887727-8b23-45d7-9730-514e8a46598f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_67d10864-2a60-4353-b195-fd3e7aa0c8bf" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_19887727-8b23-45d7-9730-514e8a46598f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_2c1f3a26-3ec8-445f-a91a-2ccc7b45d132" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_67d10864-2a60-4353-b195-fd3e7aa0c8bf" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_2c1f3a26-3ec8-445f-a91a-2ccc7b45d132" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_1aa4de52-b43d-4afa-8cd0-e7b67d7336af" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_67d10864-2a60-4353-b195-fd3e7aa0c8bf" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_1aa4de52-b43d-4afa-8cd0-e7b67d7336af" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_e8200675-a610-47ab-8581-b9277d4dffec" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_67d10864-2a60-4353-b195-fd3e7aa0c8bf" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_e8200675-a610-47ab-8581-b9277d4dffec" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_58990ec3-bf9b-4614-b827-0f298b2333a9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_67d10864-2a60-4353-b195-fd3e7aa0c8bf" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_58990ec3-bf9b-4614-b827-0f298b2333a9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour_81910fcf-e60e-4caa-871a-7e8b4e67613c" xlink:href="mgni-20220331.xsd#mgni_LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_67d10864-2a60-4353-b195-fd3e7aa0c8bf" xlink:to="loc_mgni_LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour_81910fcf-e60e-4caa-871a-7e8b4e67613c" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/DebtMaturitiesofPrincipleAmountofLongTermDebtDetails" xlink:type="simple" xlink:href="mgni-20220331.xsd#DebtMaturitiesofPrincipleAmountofLongTermDebtDetails"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/DebtMaturitiesofPrincipleAmountofLongTermDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_7633ba3c-4173-4619-ab1d-7264558eb354" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive_eb90f7db-d482-4847-8f07-4037dfba738f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_7633ba3c-4173-4619-ab1d-7264558eb354" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive_eb90f7db-d482-4847-8f07-4037dfba738f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_db18b5b5-c802-4c1b-89e9-daa873a40012" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_7633ba3c-4173-4619-ab1d-7264558eb354" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_db18b5b5-c802-4c1b-89e9-daa873a40012" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_5c97e0bd-d96b-4c78-a19a-fd0410f6dde0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_7633ba3c-4173-4619-ab1d-7264558eb354" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_5c97e0bd-d96b-4c78-a19a-fd0410f6dde0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_762d206f-7749-4e29-983b-655e3990b3fd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_7633ba3c-4173-4619-ab1d-7264558eb354" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_762d206f-7749-4e29-983b-655e3990b3fd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_7b395ab6-5b0d-4495-9cd5-b1cbb5ee05a9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_7633ba3c-4173-4619-ab1d-7264558eb354" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_7b395ab6-5b0d-4495-9cd5-b1cbb5ee05a9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_2a2e6897-ed85-46a8-b381-4b51036877dd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_7633ba3c-4173-4619-ab1d-7264558eb354" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_2a2e6897-ed85-46a8-b381-4b51036877dd" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/DebtSummaryofTermLoanBFacilityDetails" xlink:type="simple" xlink:href="mgni-20220331.xsd#DebtSummaryofTermLoanBFacilityDetails"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/DebtSummaryofTermLoanBFacilityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_8515e828-cef4-4621-b993-4ba407a1c212" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_87a5dda4-1d61-44dc-9aed-e90d8306dae0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebtNoncurrent_8515e828-cef4-4621-b993-4ba407a1c212" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_87a5dda4-1d61-44dc-9aed-e90d8306dae0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_be399dfd-7cdc-4365-ad53-527a880dfbe5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentUnamortizedDiscount"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebtNoncurrent_8515e828-cef4-4621-b993-4ba407a1c212" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscount_be399dfd-7cdc-4365-ad53-527a880dfbe5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_9bf90df7-9273-434c-9dbd-3931ae9c19e0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebtNoncurrent_8515e828-cef4-4621-b993-4ba407a1c212" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_9bf90df7-9273-434c-9dbd-3931ae9c19e0" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/DebtInterestExpenseRelatedtotheTermLoanBFacilityDetails" xlink:type="simple" xlink:href="mgni-20220331.xsd#DebtInterestExpenseRelatedtotheTermLoanBFacilityDetails"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/DebtInterestExpenseRelatedtotheTermLoanBFacilityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_72ab6a5a-5fd2-4e1e-b3f9-e0e8839ecd47" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestExpense"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_1a317127-0814-4566-a25a-abbe5ebc98c2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestExpenseDebt"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InterestExpense_72ab6a5a-5fd2-4e1e-b3f9-e0e8839ecd47" xlink:to="loc_us-gaap_InterestExpenseDebt_1a317127-0814-4566-a25a-abbe5ebc98c2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfDebtDiscountPremium_f0778797-4e68-47da-b19f-3afd4b0bf0ac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AmortizationOfDebtDiscountPremium"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InterestExpense_72ab6a5a-5fd2-4e1e-b3f9-e0e8839ecd47" xlink:to="loc_us-gaap_AmortizationOfDebtDiscountPremium_f0778797-4e68-47da-b19f-3afd4b0bf0ac" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_264cf953-4692-4ab3-bedf-25a95cb16ea0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InterestExpense_72ab6a5a-5fd2-4e1e-b3f9-e0e8839ecd47" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_264cf953-4692-4ab3-bedf-25a95cb16ea0" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.magnite.com/role/DebtAmortizationExpensefortheTermLoanBFacilityDebtDiscountandIssuanceCostsDetails" xlink:type="simple" xlink:href="mgni-20220331.xsd#DebtAmortizationExpensefortheTermLoanBFacilityDebtDiscountandIssuanceCostsDetails"/>
  <link:calculationLink xlink:role="http://www.magnite.com/role/DebtAmortizationExpensefortheTermLoanBFacilityDebtDiscountandIssuanceCostsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_71752ddd-41f1-4337-9861-4978b8abf3e1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_AmortizationOfDebtIssuanceCostsYearTwo_e3da2baa-0c73-4d2b-b623-f292df0246b7" xlink:href="mgni-20220331.xsd#mgni_AmortizationOfDebtIssuanceCostsYearTwo"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredFinanceCostsNet_71752ddd-41f1-4337-9861-4978b8abf3e1" xlink:to="loc_mgni_AmortizationOfDebtIssuanceCostsYearTwo_e3da2baa-0c73-4d2b-b623-f292df0246b7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_AmortizationOfDebtIssuanceCostsYearFive_94af712d-5f16-4de4-ba50-e54b82e45667" xlink:href="mgni-20220331.xsd#mgni_AmortizationOfDebtIssuanceCostsYearFive"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredFinanceCostsNet_71752ddd-41f1-4337-9861-4978b8abf3e1" xlink:to="loc_mgni_AmortizationOfDebtIssuanceCostsYearFive_94af712d-5f16-4de4-ba50-e54b82e45667" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_AmortizationOfDebtIssuanceCostsYearFour_902ca8bd-bec8-467b-8e54-608e35e9dc9d" xlink:href="mgni-20220331.xsd#mgni_AmortizationOfDebtIssuanceCostsYearFour"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredFinanceCostsNet_71752ddd-41f1-4337-9861-4978b8abf3e1" xlink:to="loc_mgni_AmortizationOfDebtIssuanceCostsYearFour_902ca8bd-bec8-467b-8e54-608e35e9dc9d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_AmortizationOfDebtIssuanceCostsYearThree_e1008834-b5dc-44a7-b3eb-5e36f9ee5e67" xlink:href="mgni-20220331.xsd#mgni_AmortizationOfDebtIssuanceCostsYearThree"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredFinanceCostsNet_71752ddd-41f1-4337-9861-4978b8abf3e1" xlink:to="loc_mgni_AmortizationOfDebtIssuanceCostsYearThree_e1008834-b5dc-44a7-b3eb-5e36f9ee5e67" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_AmortizationOfDebtIssuanceCostsYearOne_25f996e3-6dc4-4c47-95d7-5ef90295c321" xlink:href="mgni-20220331.xsd#mgni_AmortizationOfDebtIssuanceCostsYearOne"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredFinanceCostsNet_71752ddd-41f1-4337-9861-4978b8abf3e1" xlink:to="loc_mgni_AmortizationOfDebtIssuanceCostsYearOne_25f996e3-6dc4-4c47-95d7-5ef90295c321" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_AmortizationOfDebtIssuanceCostsRemainderOfFiscalYear_a9a7b777-a09c-48c1-866b-b549c6035df5" xlink:href="mgni-20220331.xsd#mgni_AmortizationOfDebtIssuanceCostsRemainderOfFiscalYear"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredFinanceCostsNet_71752ddd-41f1-4337-9861-4978b8abf3e1" xlink:to="loc_mgni_AmortizationOfDebtIssuanceCostsRemainderOfFiscalYear_a9a7b777-a09c-48c1-866b-b549c6035df5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_97da8eb3-91ae-4367-bc6e-90f439bc09d9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentUnamortizedDiscount"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_AmortizationOfDebtDiscountPremiumYearThree_240a4ee1-3b8b-47b3-a228-752fab131442" xlink:href="mgni-20220331.xsd#mgni_AmortizationOfDebtDiscountPremiumYearThree"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentUnamortizedDiscount_97da8eb3-91ae-4367-bc6e-90f439bc09d9" xlink:to="loc_mgni_AmortizationOfDebtDiscountPremiumYearThree_240a4ee1-3b8b-47b3-a228-752fab131442" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_AmortizationOfDebtDiscountPremiumYearFour_52452c16-0038-4433-b21b-4c5936845904" xlink:href="mgni-20220331.xsd#mgni_AmortizationOfDebtDiscountPremiumYearFour"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentUnamortizedDiscount_97da8eb3-91ae-4367-bc6e-90f439bc09d9" xlink:to="loc_mgni_AmortizationOfDebtDiscountPremiumYearFour_52452c16-0038-4433-b21b-4c5936845904" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_AmortizationOfDebtDiscountPremiumRemainderOfFiscalYear_9a0eefb1-1a37-435c-bb82-2ec07c229b9e" xlink:href="mgni-20220331.xsd#mgni_AmortizationOfDebtDiscountPremiumRemainderOfFiscalYear"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentUnamortizedDiscount_97da8eb3-91ae-4367-bc6e-90f439bc09d9" xlink:to="loc_mgni_AmortizationOfDebtDiscountPremiumRemainderOfFiscalYear_9a0eefb1-1a37-435c-bb82-2ec07c229b9e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_AmortizationOfDebtDiscountPremiumYearOne_eb53d21d-bbb3-4792-8511-ae63cbb61b91" xlink:href="mgni-20220331.xsd#mgni_AmortizationOfDebtDiscountPremiumYearOne"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentUnamortizedDiscount_97da8eb3-91ae-4367-bc6e-90f439bc09d9" xlink:to="loc_mgni_AmortizationOfDebtDiscountPremiumYearOne_eb53d21d-bbb3-4792-8511-ae63cbb61b91" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_AmortizationOfDebtDiscountPremiumYearTwo_6c140841-0238-4bd0-ac26-dcb9462e8c62" xlink:href="mgni-20220331.xsd#mgni_AmortizationOfDebtDiscountPremiumYearTwo"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentUnamortizedDiscount_97da8eb3-91ae-4367-bc6e-90f439bc09d9" xlink:to="loc_mgni_AmortizationOfDebtDiscountPremiumYearTwo_6c140841-0238-4bd0-ac26-dcb9462e8c62" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_mgni_AmortizationOfDebtDiscountPremiumYearFive_49de3c13-5ce0-458e-ab7a-c44388de62d4" xlink:href="mgni-20220331.xsd#mgni_AmortizationOfDebtDiscountPremiumYearFive"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentUnamortizedDiscount_97da8eb3-91ae-4367-bc6e-90f439bc09d9" xlink:to="loc_mgni_AmortizationOfDebtDiscountPremiumYearFive_49de3c13-5ce0-458e-ab7a-c44388de62d4" xlink:type="arc"/>
  </link:calculationLink>
</link:linkbase>
