Quick start
- Choose two legs mode or leg and hypotenuse mode.
- Enter the known side lengths.
- Add a unit label if useful.
- Press Calculate right triangle.
Best uses
Start here if one of these sounds like your job. The examples below show which inputs matter most.
- Complete a right triangle from two known side lengths.
- Find hypotenuse, missing leg, area, perimeter, and angles together.
- Check 3-4-5, 5-12-13, and other right-triangle examples.
- Copy right-triangle formula steps into notes or homework.
Choosing input mode
Use two legs mode when both shorter sides are known. The calculator finds the hypotenuse.
Use leg and hypotenuse mode when one leg and the longest side are known. The calculator finds the missing leg.
What the calculator returns
The calculator returns side lengths, area, perimeter, and the two acute angles. The third angle is always 90 degrees.
Area is reported in square units, while perimeter and side lengths use the length unit you entered.
When to use the simpler theorem tool
Use the Pythagorean Theorem Calculator when you only need one missing side.
Use this right triangle tool when you also need area, perimeter, and angles.
Worked examples for Right Triangle Calculator
c = 15
missing leg = 12
Area = 6
FAQ in plain language
What does the Right Triangle Calculator find?
It finds the missing side, hypotenuse, area, perimeter, and the two acute angles for a right triangle.
What inputs can I use?
Use two legs mode when both legs are known. Use leg and hypotenuse mode when you know one leg and the hypotenuse.
What do the main Right Triangle Calculator inputs mean?
The main inputs are the numbers, operation, mode, or known values the calculator needs. Keep units consistent, enter percentages the way the page label shows, and use the examples as a quick check before trusting the answer.
How should I read the Right Triangle Calculator answer?
Read the headline answer, then check the supporting lines and examples to understand how the calculator got there. If one input changes, rerun the tool and compare the new answer instead of guessing.
What should I double-check before trusting the Right Triangle Calculator?
Check units, signs, rounding, and the selected mode before copying the answer. If the number feels weird, rerun one of the examples first, then put your own values back in slowly.
How are the angles calculated?
After the sides are known, the calculator uses sine ratios to estimate the two acute angles. The third angle is always 90 degrees.
What formula is used for area?
Right triangle area uses A = leg a x leg b / 2 because the two legs are perpendicular base and height.
Sources
Use these if you want to compare the formula, inputs, or limits with a trusted outside explanation.
Related tools
- Pythagorean Theorem Calculator Solve a missing right-triangle side with a^2 + b^2 = c^2.
- Triangle Calculator Find triangle area, perimeter, angles, and type from three side lengths.
- Distance Calculator Find distance, delta x, delta y, and midpoint from two coordinate points.
Keep exploring
If this guide is close but not exact, these links keep you near the same kind of problem.
- Calculators Browse the full category for related tools that help with the same job.
- All free tools Search the complete Access Free Tools library by task, category, or tool name.
- All calculator and utility guides Find more plain-language examples, formulas, mistakes, and result explanations.
- Free calculator resources Start here when you are not sure which calculator page fits.
Privacy and copying results
Recent answers stay visible only while you work in the current browser tab. They are not sent to a server.
Use Copy answer when you want to save the inputs and result in notes, homework, a message, or a project list. Check the units, labels, and limits before copying.