🔺Pythagorean Theorem Calculator

Solve for any side of a right triangle given the other two, using a² + b² = c².

Side a

Side b

Hypotenuse c

Free Pythagorean Theorem Calculator

Our free Pythagorean theorem calculator solves for any missing side of a right triangle using a² + b² = c². Enter exactly two of the three sides — the two legs (a and b) or a leg and the hypotenuse (c) — and the third side is calculated instantly, with a scaled diagram showing the triangle.

Whether you're solving a geometry homework problem, checking a construction measurement, or working out the diagonal of a rectangle, this tool gives you the exact answer along with the formula and substitution shown step by step.

The Pythagorean theorem only applies to right triangles, where one angle is exactly 90°, and the hypotenuse is always the longest side, opposite that right angle. No sign-up, no downloads — everything runs instantly in your browser.