This Pythagorean theorem calculator solves right-triangle side lengths when two sides are known.
Math
Pythagorean Theorem Calculator
Solve right-triangle sides with the Pythagorean theorem.
Calculator
About this calculator
Formula notes
For a right triangle, a^2 + b^2 = c^2, where c is the hypotenuse.
Worked examples
- Example: legs 3 and 4 give hypotenuse 5, because 3^2 + 4^2 = 9 + 16 = 25.
- A right triangle with legs 9 and 12 has hypotenuse sqrt(9^2 + 12^2) = 15 and area 9 x 12 / 2 = 54.
How to use it
- Enter the two known sides.
- Identify whether you are solving for a leg or the hypotenuse.
- Read the missing side length.
Frequently asked questions
Does this work for non-right triangles?
No. The Pythagorean theorem applies only to right triangles.
How can I check whether three sides form a right triangle?
Sort them so c is longest, then test whether a^2 + b^2 equals c^2 within the measurement tolerance.
Limits and interpretation
- The theorem applies only to a right triangle; using it on an arbitrary triangle produces an invalid side relationship.
- Measured sides must share one unit, and rounded measurements can make the computed triangle appear slightly inconsistent.