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Solve a² + b² = c².
The Pythagorean Theorem Calculator solves a right triangle's unknown side. Give it the two legs to find the hypotenuse, or give it the hypotenuse and one leg to find the missing leg.
It applies the theorem a² + b² = c², which holds for every right-angled triangle and underpins distance, construction and navigation calculations.
The hypotenuse is always the longest side, so c must be greater than either leg.
In a right triangle, the square of the hypotenuse equals the sum of the squares of the other two sides: a² + b² = c².
Rearrange to a = √(c² − b²): subtract the known leg's square from the hypotenuse's square, then take the root.
Because c² equals the sum of two positive squares, c is always larger than either leg.
No — only right-angled triangles. For other triangles use the law of cosines.