Pythagorean Theorem Calculator

Use this Pythagorean Theorem Calculator to find a missing side of a right triangle from the other two sides. It also calculates the triangle’s area and perimeter.

Calculation Method

The Pythagorean theorem is:

a² + b² = c²

Where a and b are the legs and c is the hypotenuse.

To find the hypotenuse:

c = √(a² + b²)

To find a missing leg:

a = √(c² − b²)

b = √(c² − a²)

Example

For a right triangle with legs of 6 and 8:

c = √(6² + 8²)

c = √(36 + 64) = √100 = 10

The hypotenuse is 10.

Important Note

The Pythagorean theorem applies only to right triangles. The hypotenuse is always the side opposite the 90° angle and must be the longest side.

Source

• OpenStax Prealgebra 2e — The Pythagorean Theorem