Triangle Calculator

Give this calculator any three known values—some mix of sides and angles—and it reconstructs the triangle in full, returning every remaining side and angle along with the area and perimeter. That completeness is what makes it practical work: an architect detailing the triangular facades of the 2026 'Green Tower' or a surveyor mapping the irregular plots of a 2026 urban development zone needs exactly that kind of full geometric picture.

Several classical relationships do the heavy lifting. The Law of Sines (a/sin A = b/sin B = c/sin C) and the Law of Cosines (c² = a² + b² - 2ab cos C) handle most side-and-angle combinations, while area comes from Heron's formula when all three sides are known, or from 0.5 * base * height otherwise. The solver works through these step by step, pinning down each unknown from whichever triplet you supply.

Keep your angle units consistent, since the tool reads input as degrees by default. Three angles that fail to sum to 180 degrees describe a triangle that cannot exist, and that input will be rejected. Be aware too that supplying two sides and a non-included angle can yield two valid triangles—the ambiguous case—and the calculator flags when that happens.