Right Triangle Calculator
Enter any two values — the legs a and b, the hypotenuse c, or the angle α — and the solver fills in every other side, both acute angles, the area and the perimeter.
Enter any two values
Leave the values you don't know blank (or zero). The right angle is at C, between legs a and b; α is the angle opposite leg a.
How to use this calculator
1. Fill in exactly two values
Provide any two of: leg a, leg b, hypotenuse c, or the angle α in degrees. Leave the unknowns blank. At least one of the two must be a side length.
2. Click Calculate
The solver figures out which two values you gave and uses the Pythagorean theorem or trigonometry to find the rest of the triangle.
3. Read all the results
You get both legs, the hypotenuse, both acute angles, the area and the perimeter — a complete description of the triangle.
4. Watch for inconsistent input
If your hypotenuse is shorter than a leg, or an angle is outside 0–90°, the calculator shows a friendly message instead of an impossible triangle.
About right triangles
Which two values are enough?
Any two work as long as at least one is a side. Two sides, or one side plus an acute angle, fully determine a right triangle. Two angles alone only fix its shape, not its size.
The Pythagorean theorem
For legs a and b and hypotenuse c, a² + b² = c². It is used whenever you supply two sides. Explore it on its own with the Pythagorean theorem calculator.
Beyond right triangles
This tool assumes a 90° angle at C. For triangles with no right angle, use the general triangle calculator, which handles any combination of sides and angles.