ATAN

Supported, behaves as documented

Category: Math and trigonometry · Last tested 2026-09-01

Real compatibility results for the ATAN 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, 2026-08-31)	Supported, behaves as documented
LibreOffice Calc	Yes	Yes (25.8.7.3, 2026-08-31)	Supported, behaves as documented

LibreOffice version history

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

LibreOffice version	Verdict	Tested
24.2.0.3	Supported, behaves as documented	2026-08-31
24.8.7.2	Supported, behaves as documented	2026-08-31
25.2.0.3	Supported, behaves as documented	2026-08-31
25.8.7.3	Supported, behaves as documented	2026-08-31

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
=ROUND(ATAN(1),9)	Microsoft's documented worked example: arctangent of 1 in radians (pi/4)	0.785398163	0.785398163 Provenance Microsoft's page publishes this example's result as 0.785398163. Independently verified in Python: math.atan(1) = 0.7853981633974483, which is exactly pi/4 -> 0.785398163 at 9 dp	Matched
=ROUND(DEGREES(ATAN(1)),9)	The same example converted to degrees with the DEGREES function, as the page's third example does	45	45.0 Provenance Microsoft's page publishes this example's result as 45. Independently verified: pi/4 radians = 45 degrees exactly, and the double-precision conversion is exactly 45.0	Matched
=ROUND(ATAN(0),9)	The arctangent of zero	0	0.0 Provenance tan(0) = 0 and the documented output range is -pi/2 to pi/2, which contains exactly one angle with tangent zero, so ATAN(0) = 0 exactly	Matched
=ATAN("abc")	A non-numeric text argument	#VALUE!	#VALUE! Provenance #VALUE! is Excel's documented error for an argument of the wrong type; the ACOT page states it explicitly for this inverse-trigonometric family	Matched

Google Sheets (executed 2026-08-31 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
=ROUND(ATAN(1),9)	Microsoft's documented worked example: arctangent of 1 in radians (pi/4)	0.785398163	0.785398163 Provenance Microsoft's page publishes this example's result as 0.785398163. Independently verified in Python: math.atan(1) = 0.7853981633974483, which is exactly pi/4 -> 0.785398163 at 9 dp	Matched
=ROUND(DEGREES(ATAN(1)),9)	The same example converted to degrees with the DEGREES function, as the page's third example does	45	45.0 Provenance Microsoft's page publishes this example's result as 45. Independently verified: pi/4 radians = 45 degrees exactly, and the double-precision conversion is exactly 45.0	Matched
=ROUND(ATAN(0),9)	The arctangent of zero	0	0.0 Provenance tan(0) = 0 and the documented output range is -pi/2 to pi/2, which contains exactly one angle with tangent zero, so ATAN(0) = 0 exactly	Matched
=ATAN("abc")	A non-numeric text argument	#VALUE!	#VALUE! Provenance #VALUE! is Excel's documented error for an argument of the wrong type; the ACOT page states it explicitly for this inverse-trigonometric family	Matched

LibreOffice Calc 25.8.7.3 (tested 2026-08-31)

Formula	Description	Result	Expected	Verdict
=ROUND(ATAN(1),9)	Microsoft's documented worked example: arctangent of 1 in radians (pi/4)	0.785398163	0.785398163 Provenance Microsoft's page publishes this example's result as 0.785398163. Independently verified in Python: math.atan(1) = 0.7853981633974483, which is exactly pi/4 -> 0.785398163 at 9 dp	Matched
=ROUND(DEGREES(ATAN(1)),9)	The same example converted to degrees with the DEGREES function, as the page's third example does	45	45.0 Provenance Microsoft's page publishes this example's result as 45. Independently verified: pi/4 radians = 45 degrees exactly, and the double-precision conversion is exactly 45.0	Matched
=ROUND(ATAN(0),9)	The arctangent of zero	0	0.0 Provenance tan(0) = 0 and the documented output range is -pi/2 to pi/2, which contains exactly one angle with tangent zero, so ATAN(0) = 0 exactly	Matched
=ATAN("abc")	A non-numeric text argument	#VALUE!	#VALUE! Provenance #VALUE! is Excel's documented error for an argument of the wrong type; the ACOT page states it explicitly for this inverse-trigonometric family	Matched

Docs & syntax

Excel (desktop): official documentation
Google Sheets: official documentation
LibreOffice Calc: official documentation

Where ATAN behaves differently

ACOT of a negative number is off by pi in Google Sheets versus Excel and LibreOffice
Executed evidence: =ROUND(ACOT(-2),9) is -0.463647609 in Google Sheets but 2.677945045 in Excel for the web and in all four LibreOffice builds. The two branches differ by exactly pi, 180 degrees, with no error anywhere. Dates, per-engine provenance and the portable fix.