ISNUMBER Function (LibreOffice Calc)
The ISNUMBER function in LibreOffice Calc checks whether a value is a number. It is essential for data validation, conditional logic, cleaning datasets, and building robust spreadsheet workflows.
Verification status: Consult the documentation and examples below. Native application testing has not been documented for this guide. How formula examples are checked
What the ISNUMBER Function Does
- Returns TRUE if a value is numeric
- Returns FALSE for text, logical values, errors, or empty cells
- Useful for validating input and cleaning imported data
- Works with literals, formulas, and references
It is designed to be simple, reliable, and universally compatible.
Syntax
ISNUMBER(value)
Arguments
- value:
Any value, expression, or cell reference.
Basic Examples
Check if A1 contains a number
=ISNUMBER(A1)
Use with IF to validate numeric input
=IF(ISNUMBER(A1); "Valid"; "Invalid")
Check a literal number
=ISNUMBER(42)
Returns TRUE.
Check a numeric string
=ISNUMBER("42")
Returns FALSE — text is not a number.
Advanced Examples
Convert text to number before checking
=ISNUMBER(VALUE(A1))
Useful for imported numeric text.
Check if a formula returns a number
=ISNUMBER(A1 * 2)
TRUE if A1 is numeric.
Detect numbers inside mixed data
=ISNUMBER(FIND("123"; A1))
TRUE if “123” appears in A1 (FIND returns a number).
Validate numeric ranges
=AND(ISNUMBER(A1); A1 > 0; A1 <= 100)
Check if a cell contains a date
=ISNUMBER(A1)
Dates are stored as numbers in Calc.
Check if a cell contains a time
=ISNUMBER(A1)
Times are also numeric.
Detect numeric results from text functions
=ISNUMBER(LEN(A1))
LEN always returns a number → TRUE.
Edge Cases and Behavior Details
Text that looks like a number is NOT a number
=ISNUMBER("123")
Returns FALSE.
A cell containing a formula returning "" is NOT a number
=ISNUMBER("")
Returns FALSE.
A cell containing an error is NOT a number
=ISNUMBER(#N/A)
Returns FALSE.
A cell containing a boolean is NOT a number
=ISNUMBER(TRUE)
Returns FALSE.
A cell containing a date IS a number
=ISNUMBER(DATE(2024;1;1))
Returns TRUE.
A cell containing a time IS a number
=ISNUMBER(TIME(12;0;0))
Returns TRUE.
Common Errors and Fixes
ISNUMBER returns FALSE unexpectedly
Cause:
- Value is text, even if it looks numeric
- Value contains spaces or hidden characters
- Value is a formula returning text
Fix:
Use VALUE(A1) or TRIM(A1) before checking.
ISNUMBER returns TRUE unexpectedly
Cause:
- Dates and times are numeric
- FIND, LEN, ROW, COLUMN return numbers
ISNUMBER used on a range
=ISNUMBER(A1:A10)
Returns a single TRUE/FALSE based on array context; use COUNT or SUMPRODUCT instead.
Best Practices
- Use ISNUMBER to validate numeric input
- Use VALUE to convert numeric text before checking
- Use TRIM to clean whitespace
- Use AND with ISNUMBER for range validation
- Use ISNUMBER to detect dates and times
Related Patterns and Alternatives
- Use ISTEXT to detect text
- Use ISBLANK to detect empty cells
- Use ISLOGICAL to detect TRUE/FALSE
- Use VALUE to convert numeric text
- Use COUNT or COUNTIF for numeric ranges
By mastering ISNUMBER and its companion functions, you can build clean, reliable, and error‑resistant data workflows in LibreOffice Calc.
Reproducible example (tested in LibreOffice Calc)
This standalone example was calculated in LibreOffice Calc 25.2.3.2 and matched the expected value. It is a practical cross-check of one usage, not proof that every example elsewhere on this page is correct.
=ISNUMBER(3.5)
Expected result: TRUE.
Confirm that a value is numeric.
If the result differs, check the referenced cells, argument separators and number formatting. For more information, consult the LibreOffice Calc official help.