Math
Pythagorean Theorem Calculator
Calculate the hypotenuse or a missing side of a right triangle using the Pythagorean theorem. Supports all three solving modes with instant results and step-by-step calculations.
About This Tool
Use this Pythagorean Theorem Calculator to find the missing side of any right triangle. Enter any two sides and instantly calculate the third using the formula a² + b² = c².
Pythagorean Theorem
a² + b² = c²The square of the hypotenuse equals the sum of the squares of the other two sides. Rearranging the equation allows you to solve for any missing side.
Examples
Find the hypotenuse
a = 3, b = 4
Result: c = 5
Find a missing leg
c = 13, a = 5
Result: b = 12
Construction example
a = 8, b = 15
Result: c = 17
Useful for checking right angles on-site.
FAQ
What is the Pythagorean theorem?
It states that in a right triangle, the square of the hypotenuse equals the sum of the squares of the other two sides.
Can I calculate any side?
Yes. Enter any two sides and the calculator will determine the missing side automatically.
Does this work for all triangles?
No. The Pythagorean theorem only applies to right triangles with one 90° angle.
What is the hypotenuse?
The hypotenuse is the longest side of a right triangle and is always opposite the 90° angle.
Can I use decimals?
Yes. The calculator supports both whole numbers and decimal values.