Rex says
The fast lane for the math you almost remember from school. Type the numbers, get the answer, move on with your day.
Try a scenario
Click to load — tweak from there.Inputs
Leave 0 to solve for it
Result
Hypotenuse
5.0000
Side a
3.0000
Side b
4.0000
Area
6.0000
Perimeter
12.0000
Angle opposite a (°)
36.87
Angle opposite b (°)
53.13
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter side a.
- 2Enter side b.
- 3Enter hypotenuse c — Leave 0 to solve for it.
- 4Read your hypotenuse on the right — it updates as you type.
- 5Hit Share to keep the scenario or send it to someone.
About this calculator
Enter any two sides of a right triangle and get the third, plus the angles and area. Leave the side you want to solve for at zero.
Worked example
Using the values the calculator loads with:
Inputs
- Side a: 3
- Side b: 4
- Hypotenuse c: 0
Results
- Hypotenuse: 5
- Side a: 3
- Side b: 4
- Area: 6
- Perimeter: 12
- Angle opposite a (°): 36.87
- Angle opposite b (°): 53.13
What each field means
Inputs
- Side a
- The side a used in the calculation. Starts at 3 so you have a working example on load.
- Side b
- The side b used in the calculation. Starts at 4 so you have a working example on load.
- Hypotenuse c
- Leave 0 to solve for it
Results
- Hypotenuse
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Side a
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Side b
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Area
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Perimeter
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Angle opposite a (°)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Angle opposite b (°)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How does the pythagorean theorem calculator work?
Enter any two sides of a right triangle and get the third, plus the angles and area. Leave the side you want to solve for at zero. The underlying maths is: a² + b² = c², where c is the hypotenuse.
What do I need to enter?
3 values: side a, side b, and hypotenuse c. Each field starts with a sensible default, so you can change one number at a time and watch the result move.
What does the hypotenuse result mean?
It is returned as a decimal number and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds.
Is this calculator free, and do I need an account?
Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser.
How accurate is the result?
It applies the standard formula exactly, so the arithmetic is precise. Results are rounded for display; the underlying calculation keeps full precision.
Who is this tool for?
It's built for students, developers, and anyone who needs the answer right now without setting up a spreadsheet.
Accuracy and limitations
- Results are rounded for display; the underlying calculation keeps full precision.
- Very large or very small inputs may hit floating-point limits in the browser.
- Inputs outside the accepted range are clamped rather than rejected.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Pythagorean Theorem Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/pythagorean
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/pythagorean" target="_blank" rel="noopener">Pythagorean Theorem Calculator — RevenueLab</a> (2026).</p>
Source: [Pythagorean Theorem Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/pythagorean) (2026).