△ Triangle Calculator
Area, perimeter and all angles from sides
Enter all 3 side lengths (Heron's formula)
About this calculator
Solve any triangle from what you already know. Enter three known values — sides and/or angles, such as side-side-side or angle-side-angle — and the calculator finds the rest using the Law of Sines, the Law of Cosines, and the fact that angles sum to 180°. It returns the missing sides and angles, plus the area and perimeter. Works for right and non-right triangles alike.
Tip: for right triangles you only need two known values — the calculator fills in the rest with the Pythagorean theorem and basic trigonometry.