Pythagorean Theorem Calculator
Find a missing right-triangle side from the other two sides.
Enter values to calculate.
Use the right-triangle rule
Enter the two known legs to calculate the hypotenuse. The Pythagorean theorem applies only to a right triangle, so confirm that the selected sides and angle context meet that condition.
Formula
For legs a and b and hypotenuse c, a² + b² = c². If a leg is missing, rearrange the formula and take the square root of c² minus the known leg squared.
Worked example
Legs 3 and 4 produce a hypotenuse of 5. Keep all lengths in the same unit before calculating.
Frequently asked questions
Frequently Asked Questions About Online Calculators
Does this work for every triangle?
No. The Pythagorean theorem requires a right triangle.
Can I mix centimeters and meters?
Convert to one unit first.
Is the result rounded?
The displayed result is formatted for readability; keep extra precision when the measurement requires it.
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