ISNUMBER Function: syntax, examples, mistakes and translation notes
Tests whether a value is numeric.
Syntax
=ISNUMBER(value)
Arguments
value
Value or expression to test.
Worked examples
=ISNUMBER(42)
Returns TRUE.
=ISNUMBER(A2)
Helps distinguish numeric values from numbers imported as text.
Practical tips
- Use ISNUMBER during data-cleaning and lookup debugging.
- A date is normally numeric internally, so ISNUMBER can also return TRUE for valid dates.
- Use VALUE or NUMBERVALUE only when conversion is intentional.
Common mistakes
- Assuming a cell that displays digits is necessarily stored as a number.
- Treating TRUE from ISNUMBER as proof that the value meets a business range/quality rule.
Related functions
Frequently asked questions
What does ISNUMBER do?
Tests whether a value is numeric.
Why might a ISNUMBER formula return an unexpected result?
Assuming a cell that displays digits is necessarily stored as a number. Start by testing the smallest referenced range or condition independently before adding wrappers or fallbacks.
Check the complete formula
Function syntax is only one part of a working workbook. Paste the finished expression into the Formula Checker for structural warnings, the Formatter for readability or the Translator when a supported locale mapping is involved.
Testing note: examples are educational. Spreadsheet versions, locale settings, tables, named ranges and workbook data can change behavior, so validate important formulas with representative data.