How to use the Pythagorean Theorem Calculator
- Choose which side to find.
- Enter the two sides you know.
- Read the missing side, angles, area and perimeter.
What does this tool do?
In any right triangle, the square of the hypotenuse (the side opposite the right angle) equals the sum of the squares of the other two sides: a² + b² = c².
It's used everywhere from checking that a corner is square (the 3-4-5 rule) to finding distances on a map or screen.
Why use it?
- Solve for any side.
- Angles, area and perimeter included.
- Step-by-step working.
Example
A ladder 5 m long with its foot 3 m from a wall reaches √(5² − 3²) = 4 m up the wall.
The formula
c = √(a² + b²)
a = √(c² − b²)
Privacy
The calculation happens instantly in your browser. The numbers you enter are not sent to our servers or saved. There's no account to create and nothing to install.
Last reviewed by the M2Toolkit team.