Pythagorean theorem calculator
Pick the side you need, enter the other two and get the answer instantly. The calculator uses a² + b² = c² and also reports the area, the perimeter and the two acute angles of the right triangle.
Runs in your browser: nothing you enter is sent anywhere.
Frequently asked questions
What is the Pythagorean theorem?
In a right triangle the square of the hypotenuse equals the sum of the squares of the two legs, a² + b² = c². The hypotenuse c is the side opposite the right angle and is always the longest.
How do I find a missing leg?
Subtract the squares and take the root, a = √(c² − b²). For a hypotenuse of 13 and a leg of 12 the other leg is √(169 − 144) = √25 = 5.
What are Pythagorean triples?
They are whole-number sets that satisfy the theorem, such as 3-4-5, 5-12-13, 8-15-17 and 7-24-25. Any multiple of a triple works too, for example 6-8-10.
Does it work for triangles without a right angle?
No, the theorem needs a 90° angle. For other triangles use the triangle calculator, which applies the laws of sines and cosines.