Classic tool
Pythagorean Theorem Calculator
Find a missing leg or hypotenuse, plus triangle area and perimeter, from any two sides of a right triangle.
Use this Pythagorean theorem calculator to find the missing side of a right triangle without doing the equation by hand. Enter any two sides, leave the unknown side blank, and the tool returns the missing value together with the triangle perimeter and area.
How to use it
- Fill in exactly two fields.
- Use c for the hypotenuse, which must be the longest side.
- Leave blank the side you want to solve.
The base equation is a² + b² = c². If the hypotenuse is missing, the calculator adds the squares of both legs. If a leg is missing, it subtracts the square of the known leg from the square of the hypotenuse.
This page is useful for homework, classroom review, construction checks, layout measurements, geometry practice and quick answer verification.
Use clear inputs to get a more useful result.
How to use Pythagorean Theorem Calculator
Open the tool, fill in the fields with the data you already have and generate the result step by step. If you want to compare scenarios, change one field at a time so it is easier to understand the impact of each value.
When Pythagorean Theorem Calculator is useful
The goal here is simple: Find a missing leg or hypotenuse, plus triangle area and perimeter, from any two sides of a right triangle. It works well for quick checks, planning, study and review before you move to a final decision or document.
What to review before using the result
Check units, labels, numbers, timing and any context that can change the meaning of the output. If the result will be used in a quote, technical task, published page or report, finish with a manual review.
Frequently asked questions
What should I prepare before using the tool?
Keep the key values, labels and units ready before filling in the fields. Cleaner inputs make the final result easier to review and compare.
Can I test different scenarios on the same page?
Yes. The safest approach is to change one field at a time, compare the outputs and note which value actually changes the final answer.
Is the result ready to use without checking it?
It is better to treat it as support. Review the output once more before using it in a quote, document, spreadsheet, technical task or published page.