ISNA Function

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The Excel ISNA function tests specifically for the #N/A error. It returns TRUE or FALSE, making it the building block of error-proof formulas, validation, and conditional logic.

Quick answer: test a cell:
=ISNA(A2) // TRUE when the value is the #N/A error

Syntax

=ISNA(value)
ArgumentDescription
valueRequiredThe value, cell, or expression to test.

How to use it

ISNA returns TRUE when the value is the #N/A error, and FALSE otherwise. Wrap it in IF to act on the result, or sum it with SUMPRODUCT to count matches: =SUMPRODUCT(--ISNA(A2:A100)).

The IS family: ISBLANK, ISNUMBER, ISTEXT, ISLOGICAL, ISNONTEXT, ISERR, ISERROR, ISNA, ISREF, ISFORMULA, ISEVEN, and ISODD each return TRUE or FALSE so you can branch with IF, count with SUMPRODUCT, or drive conditional formatting.

Try it: interactive demo

Live demo

Pick an input and watch the formula and result update.

Result:

Practice workbook

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Frequently asked questions

ISNA vs IFNA?
IFNA replaces only #N/A in one step: =IFNA(VLOOKUP(...),"Not found"). ISNA just tests. Use IFNA to handle missing lookups cleanly.
How do I act on the TRUE/FALSE result?
Wrap it in IF: =IF(ISNA(A2), "yes", "no").
Can I count how many cells pass?
Yes: =SUMPRODUCT(--ISNA(range)) counts the TRUEs.

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Related functions: ISERROR · ISNUMBER · ISBLANK · IFERROR · NA