Pythagorean Theorem Calculator
Find the missing side of a right triangle from the other two with a² + b² = c².
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The Pythagorean Theorem
In any right triangle, the square of the hypotenuse (the side opposite the right angle) equals the sum of the squares of the two legs.
a² + b² = c² c = √(a² + b²) a = √(c² − b²)
Worked Example
Tips
Common whole-number triples: 3-4-5, 5-12-13, 8-15-17, 7-24-25, and any multiple (6-8-10). Builders use 3-4-5 to square a corner: measure 3 ft one way, 4 ft the other, and adjust until the diagonal is exactly 5 ft. The theorem only works for right triangles; for others, use the triangle solver.