01
How to use this calculator
- Identify the two sides meeting at the right angle.
- Square both lengths and add the results.
- Take the square root to obtain the hypotenuse.
02
A little understanding goes a long way.
The hypotenuse is opposite the 90-degree angle and is always the longest side of a right triangle. Use consistent units for both legs.
THE FORMULA
c = √(a² + b²)
TRY IT ON PAPER
A worked example
For legs of 3 cm and 4 cm, c = √(9 + 16) = 5 cm.
03
A few common questions
Can I use any triangle?
No. This formula applies only to right triangles.
How do I find a missing leg?
If c is the hypotenuse and a is the known leg, the other leg is √(c² − a²), with c greater than a.