Solve any right triangle from two known sides or angles
Enter Any 2 Known Values
Quick Presets
Solution
Sides
Angles
Properties
Trig Ratios (for angle A)
Formulas Used
Enter any 2 of the 5 values (sides a, b, c or angles A, B). Angles must be in degrees. C is always 90°.
A right triangle calculator lets you find all unknown sides and angles when you know any two values. Enter any combination of sides (a, b, hypotenuse c) or acute angles (A, B) and this tool instantly applies the Pythagorean theorem and trigonometric functions to solve the full triangle — including area, perimeter, and trig ratios.
Any two of the five values work: the three sides (a, b, c) or the two acute angles (A, B). Common combinations include two legs, one leg and the hypotenuse, or one side and one acute angle. Two angles alone only define the shape — you need at least one side to determine the scale.
It uses the Pythagorean theorem (a² + b² = c²) when two sides are given, and SOH-CAH-TOA trigonometry when a side and angle are known. Angles are derived from the fact that A + B = 90° in every right triangle.
The 3-4-5 and 5-12-13 triangles are Pythagorean triples with integer sides. The 45-45-90 triangle has two equal legs, and the 30-60-90 triangle has sides in a 1 : √3 : 2 ratio. Use the presets to explore these instantly.
Every triangle's interior angles sum to 180°. Since one angle is already 90° (the right angle), the remaining two acute angles must together equal 90°. If you enter both A and B and they don't sum to 90, the inputs are inconsistent and the calculator will flag the error.