When can I use the Pythagorean theorem?

Use it only for right triangles, where one angle is exactly 90 degrees.

How do I find the hypotenuse?

Square both legs, add the squares, then take the square root of the sum.

Can it find a missing leg?

Yes. Enter the hypotenuse and the other leg, and the calculator subtracts the known leg square from the hypotenuse square.

Pythagorean Theorem Calculator

Find the hypotenuse, find a missing leg, or check right-triangle side relationships with the Pythagorean theorem.

Find

Unit

Leg a (m)

Leg b (m)

Enter two sides of a right triangle. The calculator finds the third side and checks that the hypotenuse remains the longest side.

Preview (enter values for an exact diagram)schematic example

Find the missing side of a right triangle

English Pythagorean-theorem intent is direct: find the hypotenuse, find a missing leg, or verify a right-triangle relationship. This tool keeps that workflow separate from general triangle solving.

a^{2} + b^{2} = c^{2}

For a right triangle, c is the hypotenuse and a and b are the legs.

a = c^{2} - b^{2}

Use the difference of squares to recover a missing leg.

Use one length unit throughout a calculation. Linear outputs use that unit, surface areas use square units, and volume uses cubic units.

Frequently Asked Questions

Sources and References

Calculations are based on the listed reference sources. Links open in a new tab.

Updated: June 2, 2026

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