Pythagorean Theorem Calculator
Find the missing side of a right triangle — with step-by-step solution.
Leave one field empty to solve for that side.
About this calculator
Enter any two sides of a right triangle, leave the third empty, and the calculator will find the missing side using the Pythagorean theorem (a² + b² = c²). Side c is always the hypotenuse (longest side, opposite the right angle).
How the Pythagorean theorem works
The Pythagorean theorem states that in a right triangle, the square of the hypotenuse (c) equals the sum of the squares of the other two sides (a and b): a² + b² = c². To find a missing side, rearrange the equation: c = √(a² + b²) for the hypotenuse, or a = √(c² − b²) for a leg. The theorem is fundamental to geometry, trigonometry, and many real-world applications such as construction, navigation, and physics.