How to use the right triangle calculator
Enter any two of the three sides (leg a, leg b, or hypotenuse c) and leave the third blank. The calculator applies the Pythagorean theorem to find the missing side, then uses trigonometry to compute all angles. Area is ½ × a × b. Perimeter is a + b + c.
Right triangle formulas
Pythagorean theorem: a² + b² = c². Angle A: arctan(a/b). Angle B: arctan(b/a). Angle C = 90°. Area = (a × b) / 2. Perimeter = a + b + c. The two acute angles always add up to 90°.
FAQ
What is a leg vs. a hypotenuse?
In a right triangle, the two shorter sides adjacent to the 90° angle are called legs (a and b). The longest side, opposite the 90° angle, is the hypotenuse (c). The Pythagorean theorem relates them: a² + b² = c².
Why must the hypotenuse be longer than either leg?
The hypotenuse is always the longest side in a right triangle. If you enter a hypotenuse value shorter than a leg, no valid right triangle exists for those measurements.