Pythagorean theorem calculator

Enter any two sides of a right triangle (leave the unknown blank) — the calculator solves a² + b² = c² for the missing side, where c is the hypotenuse.

Tip: enter any two sides — leave the unknown blank to solve for it.

Side a
Enter two sides to solve.

How it works

The Pythagorean theorem applies only to right triangles (one 90° angle). The two shorter sides (legs) are a and b; the longest side opposite the right angle is the hypotenuse c.

  • Find c: c = √(a² + b²)
  • Find a: a = √(c² − b²)
  • Find b: b = √(c² − a²)

FAQ

What is a Pythagorean triple?

A set of three positive integers (a, b, c) that satisfy a² + b² = c² — for example (3, 4, 5), (5, 12, 13), (8, 15, 17).

Does it work for non-right triangles?

No. For oblique triangles use the law of cosines.