<?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>0001515002</rptOwnerCik>
            <rptOwnerName>Sheeley Michael J.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>118 SECOND AVENUE SE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>CEDAR RAPIDS</rptOwnerCity>
            <rptOwnerState>IA</rptOwnerState>
            <rptOwnerZipCode>52401</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>VP/COO - United Life Ins. Co.</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>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>68</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1524</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Issuer's Employee Stock Ownership Plan for self</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">This transaction represents an allocation of shares held in trust by the Issuer's Employee Stock Ownership Plan on behalf of the Reporting Person. Shares held in trust by the plan are not distributed to the Reporting Person until retirement.</footnote>
        <footnote id="F2">Represents the approximate number of shares (excluding fractionals) allocated by the trustee/administrator of the Issuer's Employee Stock Ownership Plan for the Reporting Person's benefit.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Michael J. Sheeley by Michael T. Wilkins, Attorney-in-Fact</signatureName>
        <signatureDate>2015-03-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2015-03-26
0
0000101199
UNITED FIRE GROUP INC
UFCS
0001515002
Sheeley Michael J.
118 SECOND AVENUE SE
CEDAR RAPIDS
IA
52401
0
1
0
0
VP/COO - United Life Ins. Co.
Common Stock
2015-03-26
4
A
0
68
0
A
1524
I
By Issuer's Employee Stock Ownership Plan for self
This transaction represents an allocation of shares held in trust by the Issuer's Employee Stock Ownership Plan on behalf of the Reporting Person. Shares held in trust by the plan are not distributed to the Reporting Person until retirement.
Represents the approximate number of shares (excluding fractionals) allocated by the trustee/administrator of the Issuer's Employee Stock Ownership Plan for the Reporting Person's benefit.
/s/ Michael J. Sheeley by Michael T. Wilkins, Attorney-in-Fact
2015-03-27