ISLOGICAL function

ISLOGICAL checks whether a cell contains a TRUE or FALSE value, returning TRUE only if the value is a logical value, useful for validating data types.

=ISLOGICAL(value)

Generate a ISLOGICAL formula

Describe what you need. The generator will reach for ISLOGICAL where ISLOGICAL is the right tool, and tell you when it is not.

How to get a better answer
  • Name your columns by letter and by header: "column F (Net Value)" beats "the amount column".
  • State every condition, including the negatives — "not cancelled" changes the formula's shape.
  • Say where the data starts if it is not row 1, and whether it will grow.
  • Check the settings above match your spreadsheet: the wrong argument separator is a syntax error on your machine.

Arguments

How ISLOGICAL reads its arguments
valuerequiredISLOGICAL →
ArgumentRequiredDescription
valueRequiredAny cell, range, or literal value. ISLOGICAL checks whether it is TRUE or FALSE; if value is empty, a number, text, error, or any other type, ISLOGICAL returns FALSE.

Returns

Boolean — returns TRUE if the value is a logical value, FALSE otherwise.

Availability

Excel: All · Google Sheets: Supported

Worked examples

1. Check if task completion status contains a boolean value

TaskOwnerStart DateDue DateCompleted
Database OptimizationAlice2026-09-012026-09-05true
UI RedesignBob2026-09-022026-09-10false
TestingCharlie2026-09-032026-09-08true
=ISLOGICAL(E2)

Result:

Cell E2 contains TRUE, indicating Database Optimization is completed. Since ISLOGICAL checks specifically for logical values and TRUE is a logical value, it returns TRUE. This is useful when you need to verify that a completion status is stored as a proper boolean rather than text.

2. Identify tasks with invalid completion status format

TaskOwnerStart DateDue DateCompleted
Database OptimizationAlice2026-09-012026-09-05true
UI RedesignBob2026-09-022026-09-10false
DocumentationDiana2026-09-042026-09-06Yes
Client CallEve2026-09-052026-09-051
=IF(NOT(ISLOGICAL(E4)),"Data Issue","Proper Format")

Result: Data Issue

Row 4 (Documentation) contains "Yes" as text, not a TRUE or FALSE value. ISLOGICAL(E4) returns FALSE for text strings, so NOT(ISLOGICAL(E4)) becomes TRUE, triggering the "Data Issue" message. This pattern catches data-entry errors where someone typed completion status instead of selecting a proper boolean value.

3. Count how many tasks have valid boolean completion status

TaskOwnerStart DateDue DateCompleted
Database OptimizationAlice2026-09-012026-09-05true
UI RedesignBob2026-09-022026-09-10false
TestingCharlie2026-09-032026-09-08true
DocumentationDiana2026-09-042026-09-06Yes
Client CallEve2026-09-052026-09-051
=SUMPRODUCT(--ISLOGICAL(E2:E6))

Result: 3

ISLOGICAL checks each cell in E2:E6: Database Optimization, UI Redesign, and Testing contain TRUE or FALSE (returning TRUE), while Documentation contains "Yes" (text) and Client Call contains 1 (number), both returning FALSE. The double-negative -- converts TRUE to 1 and FALSE to 0, and SUMPRODUCT totals them, yielding 3 properly formatted rows.

Common errors

Which ISLOGICAL error are you seeing?
ISLOGICAL returned an error#NAME?
Correct the spelling to exactly ISLOGICAL. The formula bar will autocomplete the correct name when you begin typing in Excel or Google Sheets.
#VALUE!
Supply exactly one argument. To check multiple cells, either call ISLOGICAL separately for each cell or use SUMPRODUCT(--ISLOGICAL(E2:E6)) to evaluate a range in one formula.
#REF!
Restore the deleted column using Ctrl+Z or update the formula to reference a valid cell containing the Completed data.
ErrorWhy it happensHow to fix it
#NAME?Misspelling ISLOGICAL as ISLOGIC or similar variant prevents the function from being recognized by the spreadsheet.Correct the spelling to exactly ISLOGICAL. The formula bar will autocomplete the correct name when you begin typing in Excel or Google Sheets.
#VALUE!Providing the wrong number of arguments, such as =ISLOGICAL(E2,E3) with two arguments or =ISLOGICAL() with none, violates the single-argument requirement.Supply exactly one argument. To check multiple cells, either call ISLOGICAL separately for each cell or use SUMPRODUCT(--ISLOGICAL(E2:E6)) to evaluate a range in one formula.
#REF!The formula references a cell or column that was deleted, leaving a broken reference that ISLOGICAL cannot evaluate.Restore the deleted column using Ctrl+Z or update the formula to reference a valid cell containing the Completed data.

Tips and when to use something else

  • ISLOGICAL only recognizes actual TRUE and FALSE values, not text strings like "true", "false", "yes", or "no". If you need to convert text to booleans, use a formula like =IF(OR(E2="true",E2="TRUE"),TRUE,FALSE).
  • Combine ISLOGICAL with IF or NOT to build data validation rules. For example, use IF(NOT(ISLOGICAL(E2)),"Check Format","Valid") to flag non-boolean entries.
  • Use TYPE instead of ISLOGICAL when you need to distinguish all data types. TYPE returns 1 for numbers, 2 for text, 4 for logical values, 16 for errors, and 64 for arrays.
  • In conditional formatting rules, apply ISLOGICAL(E2)=TRUE to highlight all cells containing proper boolean values, making data inconsistencies visually obvious in your completion status column.

Related functions

TYPEReturns a number indicating the data type of a value: 1 for numbers, 2 for text, 4 for logical values, 16 for errors, and 64 for arrays.IFThe IF function returns one value if a condition is true and another (or nothing) if it is false, letting you branch logic in a cell.NOTNOT returns the opposite Boolean value of its logical argument, turning TRUE into FALSE and FALSE into TRUE for a single logical input.ANDAND returns TRUE only if every supplied logical argument evaluates to TRUE; otherwise it returns FALSE, making it ideal for multi-condition checks.ISNUMBERChecks whether a value is a number, returning TRUE for numeric values and FALSE for text, dates, blanks, and errors.

Frequently asked questions

Why does ISLOGICAL return FALSE when my cell contains 'true' or 'false' in quotes?
ISLOGICAL only recognizes actual logical values (TRUE or FALSE), not text strings. Excel and Google Sheets treat the text string "true" differently from the boolean TRUE. If your completion status column was filled by typing text, you'll need to convert it using VALUE or a SUBSTITUTE formula before ISLOGICAL will recognize it.
Can I use ISLOGICAL to validate a checkbox column?
Yes. Checkbox columns store actual TRUE or FALSE values, so ISLOGICAL returns TRUE for them. Wrap ISLOGICAL in IF to create a data quality check: any non-boolean entries (numbers, text, missing values) will be flagged, helping you identify incomplete task assignments or data-entry errors.
What's the difference between ISLOGICAL and using IF(E2)?
IF(E2) treats any non-zero number and any non-empty text as TRUE and returns FALSE only for zero, empty cells, FALSE, and error values. ISLOGICAL returns TRUE only for the actual logical value TRUE and returns FALSE for everything else. Use ISLOGICAL when you need to verify the exact data type; use IF when you need to test truthiness.
How do I count cells that are NOT logical values to find incomplete data?
Use =SUMPRODUCT(--(NOT(ISLOGICAL(E2:E6)))) or equivalently =SUMPRODUCT(--(ISLOGICAL(E2:E6)=FALSE)). This counts cells containing numbers, text, errors, or empty cells, helping you identify how many tasks have improperly formatted completion statuses that need correction.

Need a different formula?

The full generator is not scoped to one function — describe any spreadsheet problem and it will pick.

Open the formula generator

Reviewed 2026-09-17