Right triangle calculator
Enter the two sides next to the right angle and see both angles, the hypotenuse, the area and the perimeter, with the steps.
The two sides next to the right angle of a right-angled triangle.
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.
How it works
For a right-angled triangle with legs a (opposite angle α) and b (adjacent to α):
- tan(α) = a ÷ b, so α = tan⁻¹(a ÷ b)
- β = 90° − α
- c = √(a² + b²) (Pythagorean theorem)
With a = 3 and b = 4, the hypotenuse is 5 and α ≈ 36.87°.
Units
The angles come out in degrees or radians, whichever you choose. The sides can be in any unit, as long as both are in the same one. Only need one angle from a ratio? Use the arctan calculator.
Frequently asked questions
Is the right triangle calculator free?
Yes. The right triangle 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.