Summary

ISLOGICAL returns TRUE only for the logical values TRUE and FALSE. It returns FALSE for text, numbers, blanks, and errors.

The easiest mistake here is assuming that 1, 0, or the text "TRUE" count as logical values. They do not. This function is strict.

Syntax

=ISLOGICAL(value)

You can test a cell value, a comparison, or any expression.

Arguments

• value - [required] The value you want to test.

ISLOGICAL vs Other Functions

Using ISLOGICAL

This function is useful when a cell is supposed to hold a real decision value instead of a label or numeric flag. It helps keep workflow columns consistent, especially when a sheet mixes user input with formula results.

Another good use is auditing formula output. A comparison like A1>B1 produces a logical result, so ISLOGICAL returns TRUE. That makes it helpful when a later step expects a clean TRUE or FALSE value.

Example 1 - Check a real logical value

This returns TRUE for real TRUE or FALSE values.

=ISLOGICAL(A1)

Example 2 - Reject text that looks logical

The text "TRUE" is still text.

=ISLOGICAL("TRUE") // Returns FALSE.

Example 3 - Accept a formula comparison

A comparison result is a real logical value.

=ISLOGICAL(100>50) // Returns TRUE.

Example 4 - Reject numeric flags

The number 1 is not the same thing as TRUE here.

=ISLOGICAL(1) // Returns FALSE.

Conclusion Recap

• Main job: ISLOGICAL checks for TRUE or FALSE.
• Strict rule: Text like "TRUE" and numbers like 1 do not count.
• Useful for: Decision flags and formula audits.
• Works with: Logical results from comparisons too.