How to Check for Odd Numbers with ISODD in Excel

ISODD tests whether a number is odd — and comparing two ISODD results tells you when two things match.

You will learn to

• Test whether a number is odd
• Check whether a date falls on an odd day
• Compare two ISODD results to enforce a rule

How it works

ISODD(number) returns TRUE for odd numbers and FALSE for even ones. Like ISEVEN, it truncates decimals first, so ISODD(3.9) is TRUE. Combined with DAY, it tells you whether a date falls on an odd day of the month: =ISODD(DAY(C2)).

A neat trick is comparing two ISODD results with =. ISODD(B2)=ISODD(DAY(C2)) is TRUE when both are odd or both are even — exactly what odd/even parking or alternate-day rules need.

=IF(ISODD(B2)=ISODD(DAY(C2)),"Allowed","Ticket risk")