Syntax
ISNUMBER(value)
| Parameter | Description |
|---|---|
| value | Parameter of the ISNUMBER function. |
Examples
Validate numeric input
Formula
=ISNUMBER(A1)
Returns TRUE if A1 contains a real number (42, 3.14, a date). Returns FALSE for text "42", blanks, or errors.
Conditional formatting
Formula
=ISNUMBER(SEARCH("error", A1))
Returns TRUE if A1 contains the word "error" anywhere. SEARCH returns a number (position) on match and #VALUE! on no match, so ISNUMBER detects the match.
Data type check
Formula
=IF(ISNUMBER(B2), B2*1.08, "Invalid")
Applies 8% tax only if B2 is truly numeric. Returns "Invalid" if someone typed the amount as text.
Common Errors
#VALUE!
ISNUMBER itself never errors — it always returns TRUE or FALSE for any input.
Tips
Text numbers return FALSE
"123" stored as text returns FALSE. If a column looks numeric but ISNUMBER returns FALSE, the values are text. Multiply by 1 or use VALUE to convert.
Classic SEARCH/FIND trick
=ISNUMBER(SEARCH("keyword", A1)) is a common pattern to check if text contains a substring. SEARCH returns a position (number) or an error.
Dates are numbers
ISNUMBER returns TRUE for dates because they are stored as serial numbers internally. Use ISNUMBER together with other checks if you need to distinguish dates from regular numbers.
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