Pythagorean Theorem Calculator

Find the third side of a right triangle

Quick Answer

Pythagorean Theorem Calculator: Find the third side of a right triangle. Hypotenuse c = √(a² + b²) · leg = √(c² − other leg²).

Enter any one value, the rest auto-solve

Leg a

Leg b

Hypotenuse cauto

Area Aauto

Perimeter Pauto

Diagram (updates live with input)

Step-by-step

c = √(a² + b²) = √(3.0000² + 4.0000²) = 5.0000

验证 a² + b² = 25.0000 = c² = 25.0000 ✓

A = ab / 2 = 3.0000 × 4.0000 / 2 = 6.0000

P = a + b + c = 12.0000

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How to Use

Enter known values: fill sides, radius or angles in the Pythagorean Theorem Calculator.
Auto-solve the rest: all unknowns are solved instantly — no manual derivation.
See formula and steps: the result panel shows the formula used and the substitution.
Try another case: change any known value to solve again.

Key Points

Pythagorean Theorem Calculator is a free online geometry tool — open and use, no sign-up.
All calculations run locally in your browser; your data never leaves the device.
Key capability: Find the third side of a right triangle.
Results come with formulas and reference tables so you can verify every number.

Formula & How It Works

Pythagorean theorem

a² + b² = c²

Hypotenuse c = √(a² + b²) · leg = √(c² − other leg²)

Area = ½ab · common triples: 3-4-5, 5-12-13, 8-15-17, 7-24-25

FAQ

How do I use the Pythagorean Theorem Calculator?

Open the page and fill in the input fields — results update automatically. Find the third side of a right triangle.

Are the results accurate?

Yes. Standard formulas and conversion factors are used and verified.

Is it free? Do I need to sign up?

Completely free. No registration, login or download required.

Does it work on mobile?

Yes. The responsive design works on phones, tablets and desktops.

Is my data saved?

No. Everything runs locally in your browser.

Related Guides

Source & Updates

Based on standard Euclidean geometry formulas. Last updated: 2025-07

Last updated: 2026-08-07

Formulas and content on this page are reviewed by the YiJianSuan team. For reference only — official sources prevail.

Cite this page: YiJianSuan. Pythagorean Theorem Calculator[EB/OL]. https://www.yijiansuan.com/en/c/geometry/pythagorean

Results provided by this tool are for reference only and do not constitute professional advice.