What is the syntax for ATAN in Excel?

The syntax for ATAN is: =ATAN(number)

What is ATAN (arctangent)?

ATAN is the inverse of TAN - it returns the angle whose tangent is the given number. If TAN(45°)=1, then ATAN(1)=45° (in radians: π/4 ≈ 0.785). Unlike ASIN/ACOS, ATAN accepts any real number.

What is the difference between ATAN and ATAN2?

ATAN takes one number (the tangent ratio). ATAN2 takes x,y coordinates and returns the angle, handling all four quadrants correctly. Use ATAN2 when you have coordinates; use ATAN when you have a tangent value.

How do I calculate slope angle from rise/run?

Slope angle = ATAN(rise/run). For a ramp rising 3 feet over 12 feet: =DEGREES(ATAN(3/12)) = 14.04°. This is the angle of inclination. For percentage grade: =TAN(RADIANS(angle))*100.

Math & Trig

ATAN Function in Excel

Returns the arctangent of a number in radians.

Syntax

=ATAN(number)

Arguments

number (required): Tangent value

Examples

=ATAN(1) - Arctangent of 1 - Result: 0.785 (π/4)

ATAN in reporting workflows

Use absolute references when copying formulas across rows.
For conditional totals see [SUMIF](/functions/sumif/) and [SUMIFS](/functions/sumifs/).
Filtered lists may need [SUBTOTAL](/functions/subtotal/) instead of SUM on visible cells only.

Common errors

Result between -π/2 and π/2

Use cases

Trigonometry
Angle calculations
Engineering

Frequently asked questions

What is ATAN (arctangent)? ATAN is the inverse of TAN - it returns the angle whose tangent is the given number. If TAN(45°)=1, then ATAN(1)=45° (in radians: π/4 ≈ 0.785). Unlike ASIN/ACOS, ATAN accepts any real number.
What is the difference between ATAN and ATAN2? ATAN takes one number (the tangent ratio). ATAN2 takes x,y coordinates and returns the angle, handling all four quadrants correctly. Use ATAN2 when you have coordinates; use ATAN when you have a tangent value.
How do I calculate slope angle from rise/run? Slope angle = ATAN(rise/run). For a ramp rising 3 feet over 12 feet: =DEGREES(ATAN(3/12)) = 14.04°. This is the angle of inclination. For percentage grade: =TAN(RADIANS(angle))*100.

Editorial review

Reviewed by Excel.Directory Editorial Team. Updated May 2026.