Pythagoras Theorem Calculator

Find the hypotenuse of a right triangle from the two sides.

Last updated: 25 Aug 2026

Quick answer

By the Pythagorean theorem, the hypotenuse = √(a² + b²). For example, sides 3 and 4 give a hypotenuse of 5. Enter the two shorter sides above.

Side a

Side b

Find the hypotenuse of a right-angled triangle: c = √(a² + b²).

How to use the Pythagorean theorem

What is the Pythagorean theorem?

In a right triangle, a² + b² = c², where c is the hypotenuse (longest side).

How do I find a missing shorter side?

Rearrange: a = √(c² − b²).

What is a 3-4-5 triangle?

A common right triangle where sides 3 and 4 give a hypotenuse of 5.