ISODD truncates fractions. Check that the cell is numeric and equals INT(cell) before accepting its oddness result.
Excel provides ISODD, which returns a logical result for the integer portion of a number. If a cell is already known to contain an integer, =ISODD(A2) is enough. When the worksheet accepts arbitrary input, add validation so a fraction cannot be silently classified as an odd integer.
Add a validated classification formula
=IFERROR(IF(ISNUMBER(A2),IF(A2=INT(A2),ISODD(A2),"Not an integer"),"Not a number"),"Input error")
Put this formula in B2 and fill it down beside your input column. It returns TRUE or FALSE for numeric integers, a specific message for fractions or nonnumeric cells, and an input-error message when the calculation encounters an error. The different outputs keep invalid data visible.
Reject fractions before checking parity
The distinction matters because Excel truncates a noninteger argument before ISODD checks it. ISODD(3.8) therefore returns TRUE, but 3.8 is not itself an odd integer. Microsoft's ISODD reference documents that behavior. The A2=INT(A2) guard in the longer formula checks that the original cell is already whole.
Try a small worksheet with these input and expected-result pairs: -9 gives TRUE, -8 gives FALSE, 0 gives FALSE, 9 gives TRUE, and 9.25 gives Not an integer. A blank cell or a numeric-looking value deliberately stored as text gives Not a number. An existing cell error gives Input error.
The negative examples deserve a place in the worksheet. INT rounds downward, so a negative fraction such as -9.25 does not equal its integer result and is correctly rejected. For an actual negative integer, the equality succeeds and ISODD checks it normally.
Use MOD for validated integers
If your cells are already validated as whole numbers, a remainder formula is an alternative:
=MOD(A2,2)<>0
Excel's MOD reference explains its divisor-sign rule. With the positive divisor two, a negative odd integer still produces a nonzero result. Keep the same whole-number guard when applying this alternative to unvalidated data.
Preserve original values during review
Do not use ODD as a predicate. Its job is to round to an odd integer, so the result is another number rather than a TRUE/FALSE answer. For an audit sheet, displaying an explicit classification is easier to review than changing the original values to fit the desired category.
Preserve the original input column and place formulas beside it. Review the messages before filtering for TRUE, and decide how invalid records should be corrected. If an imported identifier was rounded before it reached the sheet, a parity formula cannot reconstruct the missing digits; retain the original text during the import when exact large identifiers matter.