Pythagorean Theorem Calculator

Find any side of a right triangle. Enter the two known sides to calculate the missing one using a² + b² = c². Also calculates triangle area, perimeter, and all angles.

Right Triangle Calculator

Leave the side you want to find empty. Enter the other two.

Pythagorean Theorem

a² + b² = c² Find c (hypotenuse): c = √(a² + b²) Find a (leg): a = √(c² − b²) Find b (leg): b = √(c² − a²) Area = (a × b) / 2 Angle A = arctan(a / b) Angle B = arctan(b / a) [= 90° − A]

Common Pythagorean Triples

abc
345
51213
81517
72425
94041

Frequently Asked Questions

What is the hypotenuse?+
The hypotenuse is the longest side of a right triangle, always opposite the 90° right angle. In the formula a² + b² = c², c is the hypotenuse. It is always longer than either leg (a or b).
Can the Pythagorean theorem work with non-right triangles?+
No — the theorem only applies to right triangles. For other triangles, use the Law of Cosines: c² = a² + b² − 2ab·cos(C), which generalizes the Pythagorean theorem for any angle.

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