ISNUMBER Function in Microsoft Excel: Formula, Examples & Troubleshooting
Learn the ISNUMBER formula in Microsoft Excel: determine whether a value is numerical, with reproducible examples, expected answers and compatibility cautions.
Verification status: Official documentation referenced; example outcomes independently reasoned or arithmetically checked where stated. Not executed in Microsoft Excel. How formula examples are checked
Quick answer: Use ISNUMBER to determine whether a value is numerical. The example below supplies exact inputs and independently calculated expected results, so you can check your formula before replacing the demonstration values with real workbook data.
Verification: The function is covered by a vendor reference or its published formula catalogue. The worked outputs here are independently reasoned, not screenshots or native test results from Microsoft Excel. Check release-specific support and argument details in the referenced vendor help.
Syntax and arguments
=ISNUMBER(value)
Cell or value to evaluate for numeric type. In formula syntax, square brackets mark optional arguments; do not type square brackets into an ordinary formula unless the particular function requires array notation. The separator shown is for the example locale and might change with spreadsheet settings.
When to use it: Use VALUE only after confirming a text entry represents a safe number.
Prepare the example inputs
In an Excel workbook, format the amount and units cells as numbers before entering the formula. Use the Name Box to check the addressed cell range if the displayed value differs. These two examples use literal values, so you can enter them into blank cells without first constructing a table. Their answers are independent calculations; dates must be displayed with an actual date format.
Worked example: exact formula and expected output
=ISNUMBER(125)
Expected result: TRUE. A literal number is numeric.
- Select an unused output cell (for example H2 if the practice table occupies A1:F9).
- Enter the formula exactly as shown, including the opening equals sign and quoted text.
- Compare the displayed answer to the expected result, then inspect the source cells if it differs.
For a range formula, the row numbers include data rows only unless the example explicitly refers to headers. A result that looks plausible may still be wrong if it references the wrong column.
Second example: a different input
=ISNUMBER("125")
Expected result: FALSE. Quoted 125 is text, not a number.
This second check uses the same function with a different input, helping you identify whether the first result was coincidental or caused by a shifted reference.
Important edge cases and a common mistake
Watch out: A numeric-looking import can be text; formatting alone does not convert its type.
If this formula needs to work in older Excel releases, consult the Microsoft version markers first; the function’s presence in a Microsoft 365 workbook does not establish Excel 2013 support.
Troubleshooting in Microsoft Excel
In Excel, inspect Formulas → Evaluate Formula and check for green number-stored-as-text indicators. #NAME? suggests a misspelling or an unavailable new function. #VALUE! often indicates a wrong argument type; #SPILL! on array functions often means output cells are occupied.
If you get the wrong answer but no error, try these checks in order: (1) evaluate the simplified first example; (2) confirm the cell values and data types; (3) check the exact row and column boundaries; (4) verify quoted text, comparison operators and separators; (5) only then add more criteria or nested functions.
For a reproducible comparison with another spreadsheet product, use the same input values in both applications and record the installed version and locale. Different default matching behavior or handling of empty values can be a migration issue rather than a mathematical disagreement.
Moving this formula between spreadsheet programs
Excel generally uses commas in English-language help formulas; LibreOffice and Collabora Calc commonly use semicolons. An identically named function may still have different matching defaults, dynamic-array behavior or version support.
Related guides already published for this function: LibreOffice Calc | Apache OpenOffice Calc | Gnumeric | Apple Numbers
If a comparison tool says Not researched here, that means we do not yet have a checked guide for that software. It does not mean the software lacks this function. See the 12-program comparison tool for a guide-coverage matrix.
Official reference and editorial verification
- Microsoft Support — Excel functions (alphabetical)
- Function comparison tool
- How we verify function guides
Evidence level: Vendor-published function catalogue / formula overview, checked for this editorial batch on October 11, 2026; example outputs verified by direct reasoning/arithmetic where applicable. No execution in Microsoft Excel was performed. Some platform-, language- and release-specific edge cases remain for native testing.