Triangle Calculator
Find the hypotenuse of a right triangle, or its area from base and height.
Two of the most common triangle questions — finding the hypotenuse of a right triangle, and finding the area from base and height — come up constantly in construction, design, and geometry homework.
The Pythagorean theorem, in plain terms
For any right triangle, a² + b² = c², where c is the hypotenuse. It's used constantly for checking that a corner is truly square — the classic 3-4-5 triangle trick — or finding a diagonal distance.
Frequently asked questions
Does the hypotenuse formula work for any triangle?
No — the Pythagorean theorem only applies to right triangles.
What's the 3-4-5 triangle trick used for?
Builders use it to check a corner is a true 90° angle, since 3² + 4² = 5².