Inverse Tan Calculator

Convert a tangent ratio into its principal angle in degrees or radians.

How it works

Enter the ratio opposite ÷ adjacent. The calculator returns θ = arctan(x) in the principal range (−π/2, π/2), or (−90°, 90°). For a full-circle direction from two coordinates, use atan2 instead.

Worked example

For x = 1, arctan(1) = π/4 radians = 45°. For x = 0, the angle is 0°; for x = −1, it is −45°.

Is inverse tan the same as reciprocal tan?

No. arctan finds an angle from a ratio. The reciprocal 1/tan(θ) is cotangent.

Ratios are limited to ±1e12. Results use floating-point arithmetic and are displayed to about eight significant digits.

Reference: NIST DLMF: Inverse Trigonometric Functions.

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