Math Calculators
Pythagorean Theorem Calculator
Find a missing right-triangle side, then calculate its area and perimeter.
Free foreverRuns in your browserNo sign-up
Hypotenuse c
5
Area: 6Perimeter: 12
About the Pythagorean Theorem Calculator
The Pythagorean theorem describes every right triangle: the square of the hypotenuse equals the sum of the squares of the two legs, written as a² + b² = c².
Use Find hypotenuse when both perpendicular legs are known. Use Find a leg when you know the hypotenuse and one leg.
Along with the missing side, the calculator reports the triangle's area and perimeter, making it useful for geometry exercises, construction layouts and diagonal measurements.
Key features
- Solve for the hypotenuse
- Solve for either missing leg
- Triangle area and perimeter
- Clear triangle validity checks
How to use
- 1Choose whether to find the hypotenuse or a missing leg.
- 2Enter the two known positive side lengths.
- 3Read the missing side, area and perimeter.
Frequently asked questions
- What is the Pythagorean theorem?
- For a right triangle, a² + b² = c², where a and b are the perpendicular legs and c is the hypotenuse opposite the right angle.
- How do I find the hypotenuse?
- Square both legs, add the results, then take the square root. For legs 3 and 4, the hypotenuse is 5.
- How do I find a missing leg?
- Subtract the square of the known leg from the square of the hypotenuse, then take the square root.
- Does this work for every triangle?
- No. The Pythagorean theorem in this form applies only to right triangles with one 90-degree angle.