Hypotenuse Calculator
The hypotenuse is the longest side of a right triangle, opposite the right angle. Given the lengths of the two legs (a and b), the hypotenuse is calculated using the Pythagorean theorem: c = √(a² + b²). This calculator quickly computes the hypotenuse from the two leg lengths.
Hypotenuse formula
c = √(a² + b²)
Quick reference
| Leg a | Leg b | Hypotenuse c |
|---|---|---|
| 3 | 4 | 5.00 |
| 5 | 12 | 13.00 |
| 6 | 8 | 10.00 |
| 8 | 15 | 17.00 |
Hypotenuse calculator: frequently asked questions
What is the hypotenuse?
The hypotenuse is the longest side of a right triangle, opposite the right angle. Formula: c = √(a² + b²).
How do I use this calculator?
Enter the lengths of the two legs (a and b), and the calculator instantly finds the hypotenuse.
What are legs?
Legs are the two sides that form the right angle. The hypotenuse is opposite the right angle.
Can I use decimals?
Yes, enter any positive numbers including decimals for accurate results.
What are common leg pairs?
3-4-5, 5-12-13, 8-15-17, and 7-24-25 are classic Pythagorean triples.
Official sources
- Khan Academy: Pythagorean theorem.
- NIST: National Institute of Standards.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.