Find the hypotenuse from two legs
When both legs are known, use the Pythagorean theorem to solve the longest side.
a = 3, b = 4
c = 5, area = 6, perimeter = 12
Right Triangle Calculator
Our free right triangle calculator helps you find all properties of a right-angled triangle, including sides, angles, area, and perimeter. Enter any two values to calculate the rest.
Right Triangle Calculator
You're using two sides mode: enter the lengths of two legs, and the calculator will find the hypotenuse and all angles.
Results
Enter values and calculate to see results
What is a Right Triangle?
A right triangle has one 90-degree angle. The side opposite that angle is the hypotenuse, and the other two sides are the legs. Because one angle is fixed, a right triangle can often be solved quickly when you know two sides or one side plus one acute angle.
Right Triangle Formulas
These formulas power the calculator and explain how each missing value is solved:
| Property | Formula |
|---|---|
| Hypotenuse (c) | c = √(a² + b²) |
| Area | A = (a × b) / 2 |
| Perimeter | P = a + b + c |
How to Use the Right Triangle Calculator
- Enter any two known values (sides or angles) in the calculator.
- Click the "Calculate" button to see the results.
- The calculator will automatically find all missing sides, angles, area, and perimeter.
- If you want to perform a new calculation, click the "Reset" button and enter new values.
For the fastest result, enter the lengths of both legs. If you know one leg and one acute angle, the calculator can still solve the triangle.
Important Notes
- Since this is a right triangle calculator, one angle is always 90 degrees.
- The sum of the other two angles must equal 90 degrees (since all angles in a triangle sum to 180 degrees).
- Make sure to enter positive values for sides. Angles must be between 0 and 90 degrees.
Right Triangle Examples
Solve with one leg and one acute angle
A single leg and one acute angle are enough to determine the rest of a right triangle.
a = 10, angle A = 30°
b ≈ 17.32, c = 20, angle B = 60°
Estimate area for construction layout
Right triangles are common when checking slope, roof framing, or stair layouts.
a = 12, b = 5
c = 13, area = 30, perimeter = 30
Right Triangle Calculator FAQ
What values do I need to solve a right triangle?
You usually need two independent values. The most common combinations are two sides or one side plus one acute angle.
Can I use only two angles in a right triangle calculator?
No. Two angles describe the shape, but not the size. You still need at least one side length to calculate area, perimeter, and actual side measurements.
How is the hypotenuse calculated?
The calculator uses the Pythagorean theorem: c = sqrt(a^2 + b^2), where c is the hypotenuse and a and b are the legs.
When should I use this instead of a general triangle calculator?
Use this calculator when one angle is exactly 90 degrees. The right-triangle-specific formulas make the calculation simpler and more precise for that case.