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Pythagorean Theorem Calculator

Calculators Free Updated 21 Sep 2026
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ⓘ About this tool 🔄 Last updated 21 Sep 2026 ✓ Reviewed by TopToolAI Team

Know two sides of a right triangle? Enter them and leave the third box empty. You get the missing side, both acute angles, the area and the perimeter, and the calculation is shown.

How to use Pythagorean Theorem Calculator

Step-by-step guide to the boxes below. Open it only if you need help.
  1. 1
    Side a Text

    Length of one shorter side of the right-angled triangle.

    Example: 3

  2. 2
    Side b Text

    Length of the other shorter side.

    Example: 4

  3. 3
    Hypotenuse c Text

    The longest side, facing the right angle. Leave one of the three boxes empty to find it.

  4. 4
    Press “Calculate”

    Click the button under the boxes. If something is missing or not valid, a short message tells you which box to fix.

  5. 5
    Read your result

    Your answer appears under the button, with a short note in plain words where it helps. Change any box and press again to compare different numbers.

Go to the calculator

Enter any two sides of a right triangle and leave the third empty. Side c is the hypotenuse.

Embed this calculator on your website

Want this calculator on your own site? Copy the code below and paste it into the HTML of any page or post. It works the same as it does here. If you do not mind, leave the small link under it in place.

Pythagorean Theorem Calculator FAQs

Which side is the hypotenuse?
The one opposite the right angle. It is always the longest side.
What is a Pythagorean triple?
Three whole numbers that fit a² + b² = c², like 3-4-5 or 5-12-13.
What is the Pythagorean theorem?
In a right triangle, a² + b² = c², where c is the hypotenuse, the side opposite the right angle.
How do I find a missing side?
For the hypotenuse, c = √(a² + b²). For a leg, a = √(c² − b²). Leave one field blank in the calculator.

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