How this calculator works
This calculator finds the area, perimeter, and angles of a triangle from three side lengths. Enter three side lengths to see if they form a valid triangle and get the calculated results. Use it for geometry problems, construction, and design work. The key inputs are three side lengths. The output is the area, perimeter, and three angles. Real-world applications include geometry education, construction, design work, and triangle verification. The calculator validates the triangle inequality, uses Heron's formula for area, and applies the law of cosines for angles. Any side must be shorter than the sum of the other two sides to form a valid triangle. Angles are shown in degrees for readability. This page calculates from three known side lengths only and does not solve for missing sides.