Pythagorean Theorem Calculator
Find the hypotenuse of a right triangle.
Hypotenuse
Applies only to right triangles. Inputs must use the same units.
Formula checked · NumberSwift · Review process
How this calculator works
For a right triangle, the square of the longest side equals the sum of the squares of the other two sides. Enter those two perpendicular legs to find the hypotenuse. The relationship does not apply to arbitrary triangles. Measurements should use the same length unit for both legs.
Formula
c = √(a² + b²)
Assumptions & limitations
Applies only to right triangles. Inputs must use the same units.
Worked example
Legs 3 and 4 give a hypotenuse of 5.
To find the area of the same right triangle, use the Area Calculator with one leg as the base and the other as perpendicular height.
Our approach to calculations ↗Common questions
Which two sides should I enter?
Enter the two perpendicular legs, not the hypotenuse. The tool calculates the longest side opposite the right angle.
Can I use it for a triangle without a right angle?
No. The relationship a² + b² = c² applies to right triangles.
Does it work with different units?
Convert both legs into the same length unit first. The output uses that unit.