Triangle Calculator
Calculate triangle angles, area, perimeter, and type from the lengths of three sides.
Frequently Asked Questions
What is the Pythagorean theorem?
For right triangles, a² + b² = c², where c is the hypotenuse. This calculator uses the law of cosines, which works for all triangles.
How do I know if my triangle is valid?
A triangle must satisfy the triangle inequality theorem: the sum of any two sides must be greater than the third side.
What is an isosceles triangle?
An isosceles triangle has two sides of equal length. An equilateral triangle has all three sides equal, while a scalene triangle has all different sides.