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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-03-26</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000101199</issuerCik>
        <issuerName>UNITED FIRE GROUP INC</issuerName>
        <issuerTradingSymbol>UFCS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001451190</rptOwnerCik>
            <rptOwnerName>Wilkins Michael T</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>118 SECOND AVENUE SE</rptOwnerStreet1>
            <rptOwnerStreet2>P.O. BOX 73909</rptOwnerStreet2>
            <rptOwnerCity>CEDAR RAPIDS</rptOwnerCity>
            <rptOwnerState>IA</rptOwnerState>
            <rptOwnerZipCode>52407-3909</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Vice President &amp; COO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-03-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>23</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>214614</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By self as co-trustee of Issuer's Employee Stock Ownership Plan</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">This transaction represents a distribution of shares from the Issuer's Employee Stock Ownership Plan to someone other than the Reporting Person.</footnote>
        <footnote id="F2">The Reporting Person serves as Co-Trustee of this employee benefit plan and disclaims beneficial ownership of any Issuer securities held by this plan that are not allocated for his individual benefit.  This report shall not be deemed an admission that the Reporting Person is the beneficial owner of such securities for purposes under Section 16 of the Securities Exchange Act of 1934 or for any other purpose. Currently only 1,961 shares held in this plan are allocated specifically for the Reporting Person's individual benefit.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Michael T. Wilkins</signatureName>
        <signatureDate>2015-03-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2015-03-26
0
0000101199
UNITED FIRE GROUP INC
UFCS
0001451190
Wilkins Michael T
118 SECOND AVENUE SE
P.O. BOX 73909
CEDAR RAPIDS
IA
52407-3909
0
1
0
0
Executive Vice President & COO
Common Stock
2015-03-26
4
J
0
23
0
D
214614
I
By self as co-trustee of Issuer's Employee Stock Ownership Plan
This transaction represents a distribution of shares from the Issuer's Employee Stock Ownership Plan to someone other than the Reporting Person.
The Reporting Person serves as Co-Trustee of this employee benefit plan and disclaims beneficial ownership of any Issuer securities held by this plan that are not allocated for his individual benefit.  This report shall not be deemed an admission that the Reporting Person is the beneficial owner of such securities for purposes under Section 16 of the Securities Exchange Act of 1934 or for any other purpose. Currently only 1,961 shares held in this plan are allocated specifically for the Reporting Person's individual benefit.
/s/ Michael T. Wilkins
2015-03-26