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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-03-16</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001203171</rptOwnerCik>
            <rptOwnerName>RIFE JOHN A</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>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-03-16</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>56</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>30.21</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8448</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote #1</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2015-03-16</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F3"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>16.892</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>30.21</value>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>16.892</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2568.4234</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The number of shares (excluding frationals) beneficially held indirectly by the Reporting Person includes: 6,635 shares held in an individual retirement account for Mr. Rife's benefit; 1,379 shares heldindividually by Mr. Rife's spouse; and 434 shares held in a SEP individual retirement account for Mr. Rife's benefit.</footnote>
        <footnote id="F2">Each share of phantom stock is the economic equivalent of one share of the Issuer's common stock. The shares of phantom stock become payable, in cash, in one lump sum or prorated over five years, at the election of the Reporting Person, upon the Reporting Person's termination of service as a director.</footnote>
        <footnote id="F3">Share acquired through participation in the United Fire Group, Inc. Deferred Compensation Plan for Non-Employee Directors.</footnote>
        <footnote id="F4">The price per share is the closing price of the Issuer's common stock on the date of the reported transaction.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ John A. Rife by Barrie W. Ernst, Attorney-in-Fact</signatureName>
        <signatureDate>2015-03-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2015-03-16
0
0000101199
UNITED FIRE GROUP INC
UFCS
0001203171
RIFE JOHN A
118 SECOND AVENUE SE
P.O. BOX 73909
CEDAR RAPIDS
IA
52407-3909
1
0
0
0
Common Stock
2015-03-16
4
A
0
56
30.21
A
8448
I
See footnote #1
Phantom Stock
2015-03-16
4
A
0
16.892
30.21
A
Common Stock
16.892
2568.4234
D
The number of shares (excluding frationals) beneficially held indirectly by the Reporting Person includes: 6,635 shares held in an individual retirement account for Mr. Rife's benefit; 1,379 shares heldindividually by Mr. Rife's spouse; and 434 shares held in a SEP individual retirement account for Mr. Rife's benefit.
Each share of phantom stock is the economic equivalent of one share of the Issuer's common stock. The shares of phantom stock become payable, in cash, in one lump sum or prorated over five years, at the election of the Reporting Person, upon the Reporting Person's termination of service as a director.
Share acquired through participation in the United Fire Group, Inc. Deferred Compensation Plan for Non-Employee Directors.
The price per share is the closing price of the Issuer's common stock on the date of the reported transaction.
/s/ John A. Rife by Barrie W. Ernst, Attorney-in-Fact
2015-03-17