Information
ISLOGICAL Function in Excel
Returns TRUE if the value is a logical value (TRUE or FALSE).
Syntax
- =ISLOGICAL(value)
Arguments
- value (required): Value to test
Examples
- =ISLOGICAL(TRUE) - Test TRUE - Result: TRUE
- =ISLOGICAL("TRUE") - Test text TRUE - Result: FALSE
Defensive formulas with ISLOGICAL
- Use IS* functions inside IF to branch on blank, error, text, or number cells.
- Prefer [IFERROR](/functions/iferror/) when you only need a fallback display value.
- Error hub: [Fix formula errors](/guides/fix-excel-formula-errors/).
Common errors
- Text TRUE/FALSE returns FALSE
Use cases
- Data validation
- Type checking
- Formula debugging
Frequently asked questions
- What is ISLOGICAL in Excel? ISLOGICAL tests if a value is a Boolean TRUE or FALSE (not text). It returns TRUE only for actual logical values, not for text strings 'TRUE' or 'FALSE', numbers 1/0, or other values.
- Why does ISLOGICAL return FALSE for 1 or 0? ISLOGICAL only recognizes actual Boolean values. Numbers 1 and 0 are numeric, not logical. While Excel often treats 1 as TRUE and 0 as FALSE in calculations, they're different data types. Use =A1=TRUE or =A1=FALSE for flexible checking.
- How do I convert text TRUE/FALSE to logical values? Use =IF(UPPER(A1)="TRUE", TRUE, IF(UPPER(A1)="FALSE", FALSE, A1)) or simply =A1=TRUE for comparison. In newer Excel, =SWITCH(UPPER(A1), "TRUE", TRUE, "FALSE", FALSE) also works.
Editorial review
- Reviewed by Excel.Directory Editorial Team. Updated May 2026.