How to Check for TRUE/FALSE Values with ISLOGICAL in Excel

Make sure a yes/no column really holds TRUE and FALSE — not "Yes", 1 or the text "TRUE" — with ISLOGICAL.

You will learn to

• Test whether a cell holds a real TRUE/FALSE
• Read a consent flag safely
• Find the first invalid entry in a column

How it works

ISLOGICAL(value) returns TRUE when the value is the logical TRUE or FALSE, and FALSE for everything else — including the text "TRUE", the word "Yes" and the number 1. Imported checkbox columns are often a mix of these, and formulas that rely on them can quietly give wrong answers.

Use =IF(ISLOGICAL(B3),IF(B3,"Opted in","Opted out"),"Fix value") to read a flag safely. To jump straight to the first bad entry, search the ISLOGICAL results for FALSE: =INDEX(A2:A8,MATCH(FALSE,ISLOGICAL(B2:B8),0)).

=IF(ISLOGICAL(B3),IF(B3,"Opted in","Opted out"),"Fix value")