Arctan calculator
Enter any number and get the angle whose tangent it is, in degrees or radians. For example tan⁻¹(1) = 45°.
Fill in the fields; the answer appears here straight away.
How it's worked out
How it works
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Enter the values
Type the numbers or the formula. Decimals may use a point or a comma. No idea? Click Fill in an example.
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Instant answer
The answer appears as you type, with the most important intermediate values.
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See the working
Under "How it's worked out" you see the steps, handy for checking your own calculation.
What does arctan do?
Arctan (tan⁻¹ or atan) gives the angle that belongs to a tangent. Unlike arcsin and arccos, it works for every number, because a tangent can be any value. The principal value lies between −90° and 90°.
Finding a slope angle
The tangent of a slope angle is rise ÷ run. A road that climbs 12 m over 100 m has a gradient of 0.12, and arctan(0.12) ≈ 6.8°. For a triangle with two known sides, the right triangle calculator also gives the other angle and the hypotenuse.
Frequently asked questions
Is the arctan calculator free?
Yes. The arctan calculator is completely free, with no account, sign-up or usage limit.
How accurate is the result?
The tool calculates with your browser's number precision. For important calculations, always double-check what you entered.
Does it work on my phone?
Yes. The tool works in any modern browser on a phone, tablet or computer.