53 · Calculators

Pythagorean Theorem Calculator

Enter any two sides of a right-angled triangle to find the third, plus its area, perimeter and angles.

a² + b² = c². Fill in two sides and leave the one you want empty.

Missing side

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How to use the pythagorean theorem calculator

  1. Enter two of the three sides.
  2. Leave the side you want empty.
  3. Read the missing side and the angles.

a² + b² = c²

In a right triangle, the square of the hypotenuse (the longest side, opposite the right angle) equals the sum of the squares of the other two. Builders use 3-4-5 triangles to check corners are square.

Examples

a = 3, b = 4

c = 5

a = 5, c = 13

b = 12

Questions

Does it work for any triangle?

No, only right-angled triangles.

Which side is the hypotenuse?

The longest side, opposite the 90° angle. Enter it as c.