Solve any triangle by entering three known sides or angles. Get all sides, all angles, area, perimeter, height, and a scaled diagram — instantly, right in your browser.
Enter any three pieces of information about a triangle — three sides (SSS), two sides with the angle between them (SAS), two angles with the side between them (ASA), or the two legs of a right triangle — and the calculator solves for everything else using the Law of Cosines and Law of Sines.
Once all three sides and three angles are known, the calculator also reports the area using Heron's formula, the perimeter, and the triangle's height, then classifies the shape by its sides (equilateral, isosceles, or scalene) and by its largest angle (acute, right, or obtuse).
The diagram redraws to scale every time you calculate, so you can visually check that the proportions match the numbers you entered.
Given sufficient known values, it finds missing sides, angles, area, and perimeter.
The Law of Sines and Law of Cosines.
0.5 × base × height, or Heron's formula when only sides are known.