ONLYOFFICE ATAN Function: Inverse Tangent, Slope, Degrees and Examples

=ROUND(DEGREES(ATAN(1)),6) has independently expected result 45 degrees. =ROUND(ATAN(1),6) has expected result 0.785398 radians. The first computes a display angle from a tangent ratio of 1; the second leaves the angle in radians. These are mathematical expectations, not native ONLYOFFICE outputs.

ATAN (arctangent) takes the numeric tangent ratio of an angle and returns the inverse tangent’s principal angle. A practical example is finding a ramp angle from rise ÷ horizontal run. For finite real ratios, the mathematical principal angle lies strictly between −90° and +90° (−π/2…π/2 radians); the short vendor reference does not itself list that range or exact error codes. ATAN alone cannot determine a full-circle direction from a coordinate pair when the x sign is lost.

=ATAN(number)

Exactly what is documented: the one required numeric argument is described in the ONLYOFFICE ATAN Help Center entry (accessed 2026-10-13 UTC). No optional arguments or defaults are specified for this function. Numbers may be directly typed or supplied by referenced cells. The documentation does not provide a full table of behaviour for blank references, quoted numeric strings, Booleans, arrays, worksheet error propagation or a first-introduced version; those areas require native checking. Its input is a tangent ratio (often rise divided by horizontal run), not an angle expressed in degrees.

The named function is present in the current official Spreadsheet Editor function catalogue and the function-specific article, both checked on 2026-10-13 UTC. This is documentation confirmation, not a claim of successful calculation in any installed build. The function article is not tagged with a minimum Docs web, self-hosted Docs, or Desktop Editors release. The separate Docs changelog and Desktop Editors changelog were consulted, but no first-supported-version or complete cross-platform parity statement for ATAN was established. No native Desktop/web application or screenshot testing was available.

These formulas show the English-language function name, decimal point and comma delimiter (where more than one argument exists). ONLYOFFICE’s Advanced Settings has distinct Formula Language and Region selectors and configurable decimal/thousands separators; it does not validate any particular translated name or argument separator in this research. Check the Formula Language setting and tooltips before pasting formulas on another locale or a different editor release. The official function entry guide explains the Home and Formula insert menus, Shift+F3, equal sign, parentheses and comma-separated arguments for its English examples.

Evidence labels throughout: A statement called official-documentation checked is drawn from the linked ONLYOFFICE page; a displayed number called independently calculated was computed from the mathematical definition using Python’s math library and then rounded for readability; native ONLYOFFICE observed results: none. Correct-looking expected values do not prove the installed program has calculated them.

1. In A1, enter Tangent ratio; in B1, enter ATAN radians; in C1, enter Degrees (6 decimals).
2. Enter the exact numbers in the A column below. Negative ratios represent negative slope in this numerical exercise.
3. In B2, enter =ATAN(A2); in C2, enter =ROUND(DEGREES(B2),6). Fill B2:C2 down through row 10. The equivalent single-cell expression for C is shown in the table so it can be copied independently.
4. Compare against the independent expectations. Do not interpret these as guaranteed observed outputs on every Desktop/web version.

The independent fixture uses Python’s math.atan() on each input and converts the result to degrees. At very large ratios, the result approaches—but does not reach—±90° for any finite real ratio. No application-specific infinity handling is assumed.

Ramp inclination from measured rise and run

Put vertical rise 3 in D2, horizontal run 4 in E2, and put =ROUND(DEGREES(ATAN(D2/E2)),6) in F2. The independently calculated inclination is 36.869898°. Here rise/run is dimensionless. If the run is zero, division is undefined; do not use ATAN(D2/E2) to model vertical lines. For full quadrant and axis handling using nonzero coordinate vectors, compare the separate ATAN2 model after testing the editor.

Negative gradients are signed directions only within a restricted interval

With a rise of −3 and a positive horizontal run of 4, =ROUND(DEGREES(ATAN(-3/4)),6) has expected angle -36.869898°. Changing both x and y signs gives the same ratio, although it points in an opposite direction. ATAN cannot distinguish those opposite points.

Roof pitch from a ratio

For a roof with vertical rise 7 and horizontal run 12, =ROUND(DEGREES(ATAN(7/12)),6) has expected pitch angle 30.256437°. If you are given a percentage grade instead, first divide the percentage by 100: a grade of 12% corresponds to a ratio 0.12, so =ROUND(DEGREES(ATAN(12/100)),6) should return 6.842773°. Compare like units before interpreting the result.

Principal-angle ambiguity

TAN(RADIANS(150)) is a negative ratio. Feeding it to ATAN yields a principal angle with an independent expected value of −30°, not 150°. The tangent is periodic with 180°, so without quadrant information there are infinitely many possible original angles. Use ATAN2 on properly ordered x/y coordinates for vector directions where quadrant matters.

• Angle versus ratio: =ATAN(45) does not recover 45°; 45 is interpreted as a tangent value. For 45°, the correct tangent ratio is 1.
• Unexpected radian decimals: ATAN returns the inverse-tangent angle; convert with the separately documented DEGREES function when degrees are needed.
• Zero denominator in slope calculations: D2/E2 has an undefined mathematical ratio when E2 is zero. This article does not assign an unverified exact ONLYOFFICE error code to that case.
• Wrong quadrant or 150° becomes −30°: ATAN returns a principal interval, not a full-circle bearing.
• Tiny numerical mismatch: binary floating-point and rounding affect the last few decimals; compare the examples to an appropriate tolerance.
• Large positive/negative ratios: the mathematical angle gets close to ±90° but finite values are not identical to infinity.
• Text, blank, TRUE/FALSE, arrays and propagated errors: coercion/precise code behaviour is not documented sufficiently in the vendor’s short function page to claim a tested outcome.
• Formula entered as text: begin with =, confirm the referenced cell contains a number, and check the editor’s formula language and decimal separator.

Microsoft Excel’s ATAN(number) documentation also describes inverse tangent for a numeric ratio, expressed in radians. That is an independently documented Excel signature—not a proof that ONLYOFFICE matches Excel’s coercion, floating-point details, errors, localized formula names, or historical version availability. Other spreadsheet editors were not natively compared. In a shared workbook, test input domain, locale, and output angle units in the exact applications and releases actually used.

• ONLYOFFICE ATAN reference — official argument definition.
• ONLYOFFICE ATAN2 reference — coordinates in x-then-y order for quadrant-dependent models.
• ONLYOFFICE ASIN reference — a distinct inverse for sine ratios.
• ONLYOFFICE DEGREES — convert radian angles to degrees.
• ONLYOFFICE RADIANS — convert degree inputs to radians.

1. Function name, required syntax and argument meaning: ONLYOFFICE ATAN, checked 2026-10-13 UTC. No vendor-evidenced minimum version, exact out-of-scope value coercion or error matrix.
2. Degrees conversion: ONLYOFFICE DEGREES, checked 2026-10-13 UTC.
3. Degrees-to-radians conversion in examples: ONLYOFFICE RADIANS, checked 2026-10-13 UTC.
4. Function insertion and catalogue: ONLYOFFICE Insert Function, checked 2026-10-13 UTC.
5. Formula language, region and number separators: ONLYOFFICE Advanced Settings, checked 2026-10-13 UTC.
6. Separate Docs and Desktop release histories, unsupported first-version attribution: Docs releases and Desktop releases, checked 2026-10-13 UTC.
7. Limited comparative documentation only: Excel ATAN, checked 2026-10-13 UTC, not evidence of ONLYOFFICE runtime behaviour.