Pythagorean Theorem Calculator

About this calculator

This tool applies the Pythagorean theorem (a² + b² = c²) to a right triangle's two legs to find the length of the hypotenuse, the side opposite the right angle, and then also reports the triangle's area and perimeter using those three side lengths. The relationship holds only for right triangles, so the calculator assumes a 90-degree angle between the two given sides.

It is used by students checking geometry and trigonometry homework, and in a surprising number of practical situations: carpenters and builders squaring a corner or cutting a diagonal brace, electricians and installers figuring out the shortest cable run between two points at different heights, and anyone measuring the diagonal of a screen, room or piece of furniture from its width and height. Because the theorem shows up anywhere two perpendicular measurements need to be turned into a straight-line distance, it's one of the most reused formulas outside the classroom.