How to use the result
A right triangle has one 90 degree angle. The hypotenuse is always the longest side and sits opposite the right angle. This page is useful for layout, construction sketches, school geometry and quick checks where the two legs are known.
Example
With legs of 3 and 4, the hypotenuse is sqrt(3^2 + 4^2) = 5. The area is 3 x 4 / 2 = 6 square units.
Common mistakes
Only use this page when the two entered sides meet at a right angle. For three side lengths without a known right angle, use the general triangle calculator.
Limitations
Measurements can be in any unit as long as both legs use the same unit. The area is returned in square units and the perimeter in the original unit.
Last reviewed: 2026-05-17