Pythagorean theorem calculator for right triangle sides.
Find a missing side of a right triangle using a^2 + b^2 = c^2. Enter any two sides and leave the unknown side blank.
Find the missing side
Triangle resultEnter exactly two side lengths.
Right triangle rule
Formula
a^2 + b^2 = c^2, where c is the hypotenuse.
- The hypotenuse is always the longest side.
- Both legs must be positive values.
- This calculator only applies to right triangles.
Worked example
If a = 3 and b = 4, then c = sqrt(3^2 + 4^2) = sqrt(25) = 5. The triangle is the classic 3-4-5 right triangle.
Related learning
Use the Scientific Calculator for square roots, the trigonometry calculator guide for angle work, and the Formula Reference for geometry formulas.
FAQ
Can I use this for non-right triangles?
No. The Pythagorean theorem only works for right triangles.
What if c is smaller than a or b?
That cannot describe a valid right triangle because c must be the longest side.