Pythagorean Theorem Calculator
Solve a right triangle with a² + b² = c².
The theorem
In a right triangle, the square of the longest side (the hypotenuse, c) equals the sum of the squares of the other two sides: a² + b² = c².
Example
With sides 3 and 4, c = √(9 + 16) = √25 = 5. Going the other way, if c = 5 and a = 3, then b = √(25 − 9) = 4.
Handy facts
- Whole-number triples such as 3-4-5, 5-12-13 and 8-15-17 are called Pythagorean triples.
- Builders use 3-4-5 to check a corner is square.
- The theorem only works for right triangles (one 90 degree angle).
Frequently asked questions
Which side is the hypotenuse?
The side opposite the right angle. It is always the longest side.
Why did I get no result in the second tab?
The hypotenuse must be longer than the known side. If it is not, no right triangle exists.
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