The classic 3-4-5 right triangle, checked and confirmed, free and instant.
The Pythagorean theorem relates the three sides of a right triangle: a² + b² = c², where c is the hypotenuse (the longest side, opposite the right angle). Enter any two sides and leave the third blank to solve for it, or switch modes to check whether three given side lengths actually form a right triangle at all.
For the missing-side mode: entering the hypotenuse (c) as blank alongside sides a and b finds the hypotenuse; entering a or b as blank alongside the other two finds that leg.
It sorts your three numbers, treats the largest as the hypotenuse, and checks whether the sum of the squares of the other two exactly equals its square.
The theorem itself only applies to right triangles — use the Triangle Solver instead for a general triangle without a right angle.
Yes — both modes work with decimals, not just whole numbers.