Last updated October 6, 2026 · Report an error
A right triangle is fully determined by any two of its four key values — two legs, the hypotenuse, and one acute angle.
This calculator solves for every remaining side and angle from whichever two values you already know.
How it works
Choose which two values you know (both legs, a leg and the hypotenuse, or a side and an angle), then enter those values. The calculator applies the Pythagorean theorem and right-triangle trigonometric ratios (sine, cosine, tangent) to solve for the rest.
- Enter which two values do you know?.
- Enter leg a.
- Enter leg b.
- Enter hypotenuse (c).
- Enter angle A (degrees).
- Click Calculate to see your results.
Examples
Legs 3 and 4
A right triangle with legs 3 and 4 has a hypotenuse of exactly 5, with acute angles of 36.87° and 53.13° — the classic 3-4-5 right triangle.
Who should use it
- Solving right triangle problems for geometry or trigonometry coursework.
- Calculating a ramp, roof pitch, or diagonal measurement in a construction or DIY project.
Industry applications
- Geometry and trigonometry education
- Construction, carpentry, and engineering
Advantages
- Supports all 6 combinations of two known values (both legs, leg+hypotenuse, leg+angle, hypotenuse+angle).
- Reports both remaining sides and both acute angles in one calculation.
Limitations
- Only for right triangles — use the general Triangle Calculator for triangles without a right angle.
Common mistakes to avoid
- Selecting the wrong "known values" option for the two values actually entered, which leads to a mismatched calculation.
- Entering an angle in radians instead of degrees.
Best practices
- Double check the leg labeling (a is opposite angle A, b is adjacent to angle A) matches your diagram before reading off the results.
Tips
- The 3-4-5 triangle (and its multiples, like 6-8-10) is a common quick way to check that a corner is truly square in construction — measure 3 units one way, 4 units the other, and the diagonal should be exactly 5.
Frequently asked questions
Yes, with no signup and no limit on how many calculations you run.
In any right triangle, the two acute angles always add up to 90°, so once one is known, the other is automatically 90° minus that value.
The general Triangle Calculator handles any triangle shape using the law of sines and cosines, while this calculator is specialized for right triangles, using simpler and more direct right-triangle trigonometry.
Degrees — enter and read all angle values in degrees, not radians.