What we do
Right Triangle Calculators is an independent site with calculators for one shape: the right triangle. Enter any two known values and the right triangle calculator works out every side, angle, the area, the perimeter, and the altitude to the hypotenuse.
Most triangle calculators just give you an answer. Ours shows each formula it used and the numbers it put into it, so students can follow the method, teachers can check a worked example, and builders can see where a measurement came from.
What's on the site
- Right triangle calculator: solves from any two of eight values (either leg, the hypotenuse, either acute angle, the altitude, the area, or the perimeter).
- Pythagorean theorem calculator: finds a missing side, or checks whether three lengths form a right triangle.
- Special right triangle, 30-60-90, and 45-45-90 calculators: solve from a single side using the exact ratios.
- Formula reference and FAQ: the math behind the calculators, in plain language.
How the calculators work
Every calculation runs in your browser. Nothing you enter is sent to a server, and the tools work without an account. Each result comes with a triangle diagram drawn to scale. You can use millimeters, centimeters, meters, inches, or feet, and switch angles between degrees and radians. The Copy shareable link button copies a link that reopens the same triangle.
Results use standard double-precision floating-point math and are rounded only for display. The calculators also recognize special cases, including 30-60-90 and 45-45-90 triangles and Pythagorean triples such as 3-4-5, and show their exact ratios.
Accuracy and corrections
The solver is checked by automated tests covering each supported pair of inputs. If you still find a wrong result, a confusing step, or a typo, please tell us. Include the link from the Copy shareable link button so we can see the exact triangle you entered. We fix confirmed errors as quickly as we can.
The calculators are made for learning and general use. For structural, surveying, or other safety-critical work, check the results independently. See our terms and conditions for details.
Get in touch
Questions, feature ideas, or feedback are welcome. Visit the contact page to reach us.