Pythagorean Theorem Calculator | Free Right Triangle Tool
Find the missing side of any right triangle. Enter two sides and get the third with a visual triangle display and step-by-step solution.
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Common Pythagorean Triples
These are sets of three positive integers that satisfy a² + b² = c².
| a | b | c (hypotenuse) |
|---|---|---|
| 3 | 4 | 5 |
| 5 | 12 | 13 |
| 8 | 15 | 17 |
| 7 | 24 | 25 |
| 20 | 21 | 29 |
| 9 | 40 | 41 |
| 12 | 35 | 37 |
| 11 | 60 | 61 |
Reviewed by Emily Watson, M.Ed.
Mathematics EducatorMathematics teacher and curriculum designer with 15+ years of experience.
Pythagorean Theorem Calculator Pros & Cons
Pros
- ✅ Find hypotenuse or any missing leg
- ✅ Visual triangle display
- ✅ Step-by-step solution shown
- ✅ Free forever — no subscriptions
- ✅ Works offline after page load
Cons
- ✗ Right triangles only (not oblique)
- ✗ No angle calculation support
Frequently Asked Questions
What is the Pythagorean theorem?
In a right triangle, a² + b² = c², where c is the hypotenuse (longest side).
How do you find the hypotenuse?
c = √(a² + b²). For a=3, b=4: c = √(9+16) = 5.
How do you find a missing leg?
a = √(c² - b²). Subtract the known leg squared from hypotenuse squared, then take the square root.
Does this work for non-right triangles?
No. The Pythagorean theorem only applies to right triangles (triangles with one 90° angle).
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