Quick start
- Choose whether to find the hypotenuse, leg a, or leg b.
- Enter the two known side lengths.
- Add a unit label if useful.
- Press Calculate side to solve the missing side.
Best uses
Start here if one of these sounds like your job. The examples below show which inputs matter most.
- Find the hypotenuse when both legs are known.
- Find a missing leg when one leg and the hypotenuse are known.
- Check right triangle side lengths for homework.
- Copy formula steps for Pythagorean theorem practice.
When the theorem applies
The Pythagorean theorem only works for right triangles. The hypotenuse is always the side opposite the 90-degree angle.
If the triangle is not a right triangle, use the Triangle Calculator instead.
Finding the hypotenuse
When both legs are known, the calculator uses c = sqrt(a^2 + b^2).
The hypotenuse should always be longer than either leg.
Finding a missing leg
When the hypotenuse and one leg are known, the calculator subtracts the known leg squared from the hypotenuse squared, then takes the square root.
If the known leg is longer than the hypotenuse, the input cannot describe a real right triangle.
Worked examples for Pythagorean Theorem Calculator
c = 5
a = 5
b = 15
FAQ in plain language
What formula does the calculator use?
It uses the Pythagorean theorem: a^2 + b^2 = c^2, where c is the hypotenuse of a right triangle.
Can it solve for a missing leg?
Yes. If you know the hypotenuse and one leg, it subtracts the known leg squared from the hypotenuse squared, then takes the square root.
What do the main Pythagorean Theorem 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 Pythagorean Theorem 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 Pythagorean Theorem 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.
Does the Pythagorean theorem work for every triangle?
No. It only applies to right triangles with one 90-degree angle.
What if the hypotenuse is shorter than a leg?
That input is invalid for a right triangle. The hypotenuse must be the longest side.
Sources
Use these if you want to compare the formula, inputs, or limits with a trusted outside explanation.
Related tools
- Right Triangle Calculator Solve right triangle sides, area, perimeter, and acute angles.
- Distance Calculator Find distance, delta x, delta y, and midpoint from two coordinate points.
- Triangle Calculator Find triangle area, perimeter, angles, and type from three side lengths.
Keep exploring
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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.