Calculate the arctangent (inverse tangent) of any real number and return the angle in degrees and radians.
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Result
The angle whose tangent equals 0.
Also in Functions
Trigonometry
The arctan calculator finds the angle whose tangent equals a given value. Unlike arcsin and arccos, arctangent accepts any real number — the result always falls between -90° and 90°.
Arctangent (tan⁻¹ or atan) is the inverse of the tangent function. If tan(45°) = 1, then arctan(1) = 45°. The result range is (-90°, 90°) or (-pi/2, pi/2).
As the input grows very large, arctan approaches 90°. As it goes to negative infinity, it approaches -90°. The function is defined for all real numbers.
Arctangent returns the principal value only. For the full-range inverse tangent that distinguishes quadrants, use atan2(y, x) — not covered by this calculator.
Frequently asked questions
0 degrees. tan(0°) = 0, so arctan(0) = 0°.
45 degrees (pi/4 radians). tan(45°) = 1.
Related
These related calculators come from the same leaf category, nearby sibling categories, or the same top-level topic.
Calculate the arccosine (inverse cosine) of a value and return the angle in degrees and radians with exact fractions of pi.
Calculate the arcsine (inverse sine) of a value and return the angle in degrees and radians with exact fractions of pi.
Calculate the tangent of an angle in degrees or radians with undefined-angle detection at 90 and 270 degrees.
Calculate the sine of an angle in degrees or radians with exact values for common angles like 30, 45, and 60 degrees.
