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Pythagorean Theorem Calculator

Find the missing side of a right-angled triangle, plus all its angles.

Result

5

c = 5

Area

0

Perimeter

0

In a right-angled triangle a² + b² = c², where c is always the longest side and sits opposite the 90° angle. A 3-4-5 triangle is the classic example.

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What Is Pythagorean Theorem Calculator?

The Pythagorean Theorem Calculator finds the missing side of a right-angled triangle from the other two, then gives the area, perimeter, and all three angles. The triangle is drawn to scale so you can check the shape visually.

Who Uses the Pythagorean Theorem Calculator?

Students use it for trigonometry and geometry homework, and tradespeople use it to check diagonal lengths before cutting or bracing material.

How to Use the Pythagorean Theorem Calculator

  1. Choose which side to calculate: the hypotenuse, a, or b.
  2. Enter the two known side lengths.
  3. Read the missing side, area, perimeter, and angles.

Why Choose Our Pythagorean Theorem Calculator?

  • Finds any of the three sides
  • Rejects impossible triangles instead of returning a bad number
  • Drawn to scale with labelled angles

Try the Pythagorean Theorem Calculator above — it is free, fast, and works on any device. Bookmark this page to return whenever you need it.