RightSizeTools Practical sizing calculators
Geometry Basics

Right Triangle Calculator

Enter the two square sides of a right triangle. The calculator returns the diagonal side, area, perimeter, and approximate angles.

Last updated: May 2026

Unit system Switch between U.S. customary and metric units. Your choice is remembered on other calculators.

Right triangle legs

Use the two sides that meet at the 90° corner. The result is the diagonal side across from the right angle.

Visual guide

Which measurement goes where?

Enter the two legs that meet at the 90° corner. The diagonal side is the hypotenuse.

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Buying and sizing notes

How to use this estimate

What this includes

  • The required inputs shown on this page
  • common planning assumptions
  • optional advanced adjustments where provided

What it does not include

  • site-specific professional design
  • local code approval
  • manufacturer-specific requirements
  • installation quality

Common mistakes

  • Leaving a required input at the default when your situation is different
  • ignoring product labels or ratings
  • treating the estimate as an exact final answer

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