TopToolsAiFind the missing side of a right triangle with the Pythagorean theorem. Enter any two sides to get the third, plus the area, perimeter, both acute angles and the working steps.
Last updated: 21 Sep 2026
How to use Pythagorean Theorem Calculator
- Enter the two sides you know: a and b, or one leg and the hypotenuse c.
- Leave the unknown side empty.
- Click Calculate to get the missing side, angles, area and the working.
Frequently asked questions
Which side is the hypotenuse?
The hypotenuse (c) is the side opposite the right angle. It is always the longest side of the triangle.
What is a Pythagorean triple?
Three whole numbers that satisfy a² + b² = c², such as 3-4-5 or 5-12-13.
Is this calculator free to use?
Yes, it is completely free, with no signup or account required.
Does my data get uploaded anywhere?
No. Everything is calculated in your browser and nothing is sent to our servers.
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