Which side is the hypotenuse?
The hypotenuse c is opposite the right angle and is the triangle’s longest side.
Pythagorean Theorem Calculator
Find a missing side of a right triangle using a² + b² = c².
Calculations happen locally. We do not send your values to our server.
Example
With legs of 3 and 4, the hypotenuse is 5 because 3² + 4² equals 5².
Calculation method
For a right triangle, c=√(a²+b²). To find a leg, the known leg squared is subtracted from the hypotenuse squared before taking the square root.
Important notes
The hypotenuse must be longer than either leg. This relationship applies only to right triangles.
Frequently asked questions
Can I use any measurement unit?
Yes. Use the same unit for known sides and the answer will use that unit.
Does this work for non-right triangles?
No. Use a law-of-cosines method when the included angle is not 90 degrees.