Pythagorean Theorem Calculator

a² + b² = c². Calculate any side of a right triangle.

What this calculator does

Enter two sides to calculate the third.

When to use this calculator

This tool is most valuable when you need a result to compare against something else: a quoted figure, a competing option, or a budget threshold. Accurate comparisons require accurate inputs and arithmetic — this calculator ensures both.

Common mistakes

Many errors with this type of calculation stem from unit inconsistency: mixing metric and imperial, or mixing annual and monthly rates. Ensure all inputs use the same unit system before running the calculation.

Real-world scenarios

A business owner spots that revenue grew from £180,000 last year to £213,400 this year. The calculator confirms the increase is 18.6% — a figure needed for the annual report and for comparing against the industry growth rate cited in the sector report.

Frequently asked questions

What is the Pythagorean theorem?

In a right triangle: a² + b² = c², where c is the hypotenuse.