Inverse Tangent Calculator
Enter a value to get arctan(x) in degrees, radians and multiples of π. To find an angle from a right triangle, or a direction in all four quadrants, switch to the two-side mode (atan2).
Results update as you type.
- arctan(1) in degrees
- 45°
- In radians
- 0.7853981634
- In terms of π
- 0.25π
Steps
- tan⁻¹(1) = 0.7853981634 rad
- 0.7853981634 × 180/π = 45°
Worked example
Example: a ramp rises 1 m over 4 m
- tan θ = opposite ÷ adjacent = 1 ÷ 4 = 0.25
- θ = tan⁻¹(0.25) = 0.24498 rad
- × 180/π = 14.036°
The ramp angle is about 14.04°.
Formula
θ = tan⁻¹(x), range −90° to 90°
θ = atan2(y, x), range −180° to 180°
atan2 uses the signs of both sides to place the angle in the correct quadrant, which plain arctan can't do.
Frequently asked questions
What is arctan(1)?
45°, or π/4 radians.
Is tan⁻¹ the same as 1/tan?
No. tan⁻¹ is the inverse function (an angle); 1/tan is the cotangent.
How do I do inverse tan on a calculator?
Press SHIFT or 2nd, then TAN. Make sure the calculator is in the right angle mode (DEG or RAD).
Last reviewed October 17, 2026 · Calculations run in your browser; nothing you enter is sent to a server.