Pythagorean Theorem Calculator

What is the Pythagorean Theorem Calculator?

Find the hypotenuse of a right triangle from its two legs. The Pythagorean theorem finds the longest side of a right triangle from the other two, one of the most useful formulas in building and design.

How to use the Pythagorean Theorem Calculator

1. Enter your leg a, your leg b.
2. Results update automatically as you type; you can also press Calculate.
3. Read the output: hypotenuse c, area, angle opposite a.
4. Use the 📊 chart to see the result visually, then copy or share it.

Formula and method

Worked example

With leg a = 3, leg b = 4, the Pythagorean Theorem Calculator returns hypotenuse c: 5; area: 6; angle opposite a: 36.8699°.

Where the Pythagorean Theorem Calculator helps in real life

You need a ladder to reach a window 4 meters up, with the base 1.5 meters from the wall. The calculator gives a ladder length of about 4.27 meters.

A carpenter checks that a frame is square by measuring 3 ft along one side and 4 ft along the other. The diagonal should be exactly 5 ft.

Common mistakes to avoid

• Using it on triangles without a right angle.
• Adding the sides instead of their squares.
• Forgetting to take the square root at the end.
• Entering the hypotenuse as one of the legs.

💡 Practical tip: A 3-4-5 triangle is a quick, tool-free way to check that a corner is exactly 90 degrees.

Tips for better results

• Confirm the triangle has a 90° angle first.
• Use 3-4-5 or 6-8-10 triangles to check corners are square.
• Use the right triangle calculator when you know an angle.

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