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Pythagorean Theorem Calculator

Find the missing side of a right triangle with a² + b² = c².

Results update as you type.

Hypotenuse c

5
Area
6
Perimeter
12
Hypotenuse c5

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How it works

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 sides.

Formula

c = √(a² + b²)
a = √(c² − b²)

Example

Legs of 3 and 4: c = √(9 + 16) = 5.

Assumptions & limitations

  • Results are rounded for display.

Frequently asked questions

Does this work for any triangle?

Only right triangles (one 90° angle).