Right Triangle Calculator
Give this calculator any two sides of a right triangle and it solves the whole triangle: the third side from the Pythagorean theorem, both acute angles, the area and the perimeter.
Results
Formula
How to use this calculator
- Choose whether you know both legs or a leg plus the hypotenuse.
- Enter the two side lengths.
- Press Calculate for the complete solved triangle.
Worked example
Legs of 3 and 4.
- Hypotenuse: √(3² + 4²) = √25 = 5.
- Angles: arcsin(3/5) ≈ 36.87° and 53.13°.
- Area: 3 × 4 ÷ 2 = 6; perimeter: 3 + 4 + 5 = 12.
Result: The classic 3-4-5 triangle: hypotenuse 5, area 6, perimeter 12.
Frequently asked questions
Which side is the hypotenuse?
Always the side opposite the 90° angle — and always the longest side of a right triangle.
What is a Pythagorean triple?
Whole-number sides that satisfy a² + b² = c², like 3-4-5 and 5-12-13. Triples are useful for laying out exact right angles in construction.
Can I solve with one side and one angle instead?
That needs sine/cosine/tangent ratios for the known angle. This calculator covers the two-side cases, which include the most common homework and layout problems.
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