ISNUMBER
Quirk foundCategory: Information · Last tested 2026-09-01
Real compatibility results for the ISNUMBER function: executed in Excel for the web, Google Sheets and LibreOffice Calc, with desktop Excel behavior from Microsoft’s official documentation (we do not run desktop Excel — Excel for the web is a different application and is executed separately). Syntax and links to that documentation are below.
Support matrix
| Engine | Documented | Live-tested | Verdict |
|---|---|---|---|
| Excel (desktop) | Yes | No — documented only | n/a |
| Excel for the web | — | Yes (recalc, 2026-09-01) | Supported, behaves as documented |
| Google Sheets | Yes | Yes (Drive import, 2026-08-29) | Supported, behaves as documented |
| LibreOffice Calc | Yes | Yes (25.8.7.3, 2026-07-29) | 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 | 2026-08-29 |
| 24.8.7.2 | Quirk found | 2026-08-29 |
| 25.2.0.3 | Quirk found | 2026-08-29 |
| 25.8.7.3 | Quirk found | 2026-07-29 |
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.
Provenance
ISNUMBER(TRUE) = FALSE; use ISLOGICAL to detect booleans instead.; MISMATCH vs expected: expected False, got True
Executed test cases
Excel for the web (executed 2026-09-01 via OneDrive recalculation)
These values come from Excel for the web, not from desktop Excel. They are two different implementations of the calculation engine, and this run measured only the web one: the corpus was uploaded to OneDrive as .xlsx, recalculated by Excel for the web on open, and downloaded again for readback. Excel for the web is a rolling service with no pinnable version, so the run is identified by its date. Where a value here disagrees with the Expected column — which is Microsoft’s documentation of the desktop product — we cannot tell you whether the web engine diverges from the desktop one or the documentation is wrong about both, because we do not run desktop Excel.
| 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. | False | FalseProvenanceISNUMBER(TRUE) = FALSE; use ISLOGICAL to detect booleans instead. |
Matched |
| =ISNUMBER(A1) | A blank cell -> FALSE | False | False | Matched |
Google Sheets (executed 2026-08-29 via Drive import)
Google Sheets is a rolling service with no pinnable version, so this run is identified by its date. The corpus was imported to Drive as .xlsx, recalculated by Sheets, and exported back for readback.
| 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. | False | FalseProvenanceISNUMBER(TRUE) = FALSE; use ISLOGICAL to detect booleans instead. |
Matched |
| =ISNUMBER(A1) | A blank cell -> FALSE | False | False | Matched |
LibreOffice Calc 25.8.7.3 (tested 2026-07-29)
| 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 | FalseProvenanceISNUMBER(TRUE) = FALSE; use ISLOGICAL to detect booleans instead. |
Mismatch |
| =ISNUMBER(A1) | A blank cell -> FALSE | False | False | Matched |
Docs & syntax
- Excel (desktop): official documentation
- Google Sheets: official documentation
- LibreOffice Calc: official documentation
Related how-to recipes
- How to average a range that contains errors
- How to check if a cell contains any word from a list
- How to check if a cell contains specific text
- How to sum a column that contains errors
Where ISNUMBER behaves differently
- MAXA, MINA, AVERAGEA, VARPA vs MAX, MIN, AVERAGE, VAR.P
The A-variants count text as 0 and TRUE as 1; the plain ones ignore them. Executed: LibreOffice implements all four A-variants faithfully, but its VAR.P returns 8.2222 on {4, 8, TRUE} where Microsoft documents 4 and Google Sheets returns 4 - a silent wrong number in all four builds tested. - DOLLARDE and DOLLARFR: fractional bond prices across engines
Executed: all eight valid DOLLARDE/DOLLARFR conversions match Microsoft's documented values in LibreOffice 25.8.7.3 and Google Sheets, including the documented truncation of a non-integer fraction. All four error cases return #VALUE! in LibreOffice where #DIV/0! or #NUM! is documented; Google Sheets returns the documented code. - FVSCHEDULE: LibreOffice drops text in the rate schedule
Microsoft documents any non-numeric value in FVSCHEDULE's schedule as #VALUE!. Executed, LibreOffice 25.8.7.3 returns 1.09 for =FVSCHEDULE(1,A1:A2) with A2 = "x" - a compounding period silently dropped - while Google Sheets returns #VALUE! as documented. - ISNUMBER(TRUE) is FALSE in Excel but TRUE in LibreOffice
In Excel a logical value is not a number, so ISNUMBER(TRUE) is FALSE - executed Google Sheets agrees. LibreOffice returns TRUE. The silent divergence and a safe rewrite. - TYPE(TRUE): Excel 4 vs LibreOffice 1
Excel documents TYPE(TRUE) as 4 and TYPE(A1:A3) as 64; LibreOffice returns 1 for both. The booleans-are-numbers theme breaks logic that branches on TYPE codes.