ISNUMBER

Quirk found

Category: Information · Last tested 2026-08-06

Real, executed compatibility results for the ISNUMBER function across Microsoft Excel, Google Sheets, and LibreOffice Calc — verified by actually running it. Syntax and links to each vendor’s official documentation are below.

Support matrix

Engine	Documented	Live-tested	Verdict
Excel	Yes	Not yet	n/a
Google Sheets	Yes	Not yet	n/a
LibreOffice Calc	Yes	Yes (25.8.7.3, 2026-08-06)	Quirk found

LibreOffice version history

We executed the same test cases under each LibreOffice release to show exactly when ISNUMBER’s support changed — not documentation claims, real results.

LibreOffice version	Verdict	Tested
24.2.0.3	Quirk found	2026-07-19
24.8.7.2	Quirk found	2026-07-19
25.2.0.3	Quirk found	2026-07-24
25.8.7.3	Quirk found	2026-08-06

Why isn't ISNUMBER working in LibreOffice?

ISNUMBER exists in LibreOffice 25.8.7.3, but it is not a drop-in match for Excel — our executed tests found real behavioral differences (detailed in the test results on this page). If a formula that works in Excel or Google Sheets misbehaves in LibreOffice, compare your usage against the failing cases above before assuming your data is wrong.

Discovered quirks

=ISNUMBER(TRUE) on LibreOffice Calc returned True, but the documented/expected result is False. ISNUMBER(TRUE) = FALSE; use ISLOGICAL to detect booleans instead.; MISMATCH vs expected: expected False, got True

Executed test cases

LibreOffice Calc 25.8.7.3 (tested 2026-08-06)

Formula	Description	Result	Expected	Verdict
=ISNUMBER(A1)	A genuine number -> TRUE	True	True	Matched
=ISNUMBER(A1)	A text string -> FALSE	False	False	Matched
=ISNUMBER(TRUE)	Documented divergence/point of confusion: a logical TRUE/FALSE value is its own distinct type in Excel's IS-function type system and is NOT considered a number, even though it participates in arithmetic as 1/0. Microsoft's IS-functions page (https://support.microsoft.com/en-us/office/is-functions-0f2d7971-6019-40a0-a171-f2d869135665) states value arguments 'are not converted' and gives ISLOGICAL as the dedicated test for booleans, distinct from ISNUMBER -- the docs do not give an explicit ISNUMBER(TRUE) example, but this is the well-established, widely verified real Excel result.	True	False ISNUMBER(TRUE) = FALSE; use ISLOGICAL to detect booleans instead.	Mismatch
=ISNUMBER(A1)	A blank cell -> FALSE	False	False	Matched

Docs & syntax

Excel: official documentation
Google Sheets: official documentation
LibreOffice Calc: official documentation