<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-12-22</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000104889</issuerCik>
        <issuerName>Graham Holdings Co</issuerName>
        <issuerTradingSymbol>GHC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001605148</rptOwnerCik>
            <rptOwnerName>Rosen Andrew Stephen</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O GRAHAM HOLDINGS 1300 NORTH 17TH ST</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 1700</rptOwnerStreet2>
            <rptOwnerCity>ARLINGTON</rptOwnerCity>
            <rptOwnerState>VA</rptOwnerState>
            <rptOwnerZipCode>22209</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Vice President</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class B Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-12-22</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>G</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value>E</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>3000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>36936</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Class B Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Family Trust</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">On December 22, 2021, the reporting person contributed 3,000 shares of Class B common stock to the Andrew S. Rosen 2021 Family Trust, of which the reporting person's spouse is a trustee. The beneficiaries of the trust are the reporting person's spouse and children. The reporting person disclaims beneficial ownership of the securities held by the trust.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Nicole M. Maddrey for Andrew Stephen Rosen</signatureName>
        <signatureDate>2021-12-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2021-12-22
0
0000104889
Graham Holdings Co
GHC
0001605148
Rosen Andrew Stephen
C/O GRAHAM HOLDINGS 1300 NORTH 17TH ST
SUITE 1700
ARLINGTON
VA
22209
0
1
0
0
Executive Vice President
Class B Common Stock
2021-12-22
5
G
0
E
3000
0
D
36936
D
Class B Common Stock
3000
I
By Family Trust
On December 22, 2021, the reporting person contributed 3,000 shares of Class B common stock to the Andrew S. Rosen 2021 Family Trust, of which the reporting person's spouse is a trustee. The beneficiaries of the trust are the reporting person's spouse and children. The reporting person disclaims beneficial ownership of the securities held by the trust.
/s/ Nicole M. Maddrey for Andrew Stephen Rosen
2021-12-23