Pythagorean Theorem Calculator

Calculate a missing side of a right triangle using the Pythagorean theorem quickly and accurately.

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Enter Triangle Values

Enter any two known sides

Side A

Side B

Hypotenuse C (optional)

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Enter any two sides of a right triangle and click Calculate Missing Side.

Calculation Complete

Hypotenuse C

The missing side of the right triangle.

Side A

Side B

Hypotenuse C

Area

Side A 3

Side B 4

Hypotenuse C 5

Perimeter 12

Area 6

3² + 4² = 5²

Left side 9 + 16 = 25

Right side 25

Verification ✓ Correct

Angle A 36.87°

Angle B 53.13°

Right Angle 90°

Result: The missing hypotenuse is 5 units.

This calculator assumes a valid right triangle and uses the Pythagorean theorem: a² + b² = c², where c is the hypotenuse.

Manual calculations work, but an online tool offers key advantages for students, teachers, builders, and hobbyists alike:

100% Accuracy: Avoid small calculation mistakes, misplaced decimals, or square root errors.
Saves Time: Get instant answers instead of working through multi-step equations on paper.
Everyday Practicality: Perfect for real-world applications like framing a wall, laying out square garden beds, or measuring diagonal screen sizes.
Completely Free: Access our Free Pythagorean Theorem Calculator anytime from your phone, tablet, or desktop computer without downloading extra software.