๐Law of Cosines Calculator
Solve triangles using cยฒ = aยฒ + bยฒ โ 2abยทcos C, for SAS (find a side) or SSS (find angles).
Free Law of Cosines Calculator
Find a missing side or angle in any triangle with our free Law of Cosines Calculator, using cยฒ = aยฒ + bยฒ โ 2abยทcos C. Enter two sides and the included angle (SAS) to find the third side, or all three sides (SSS) to find any angle โ with full step-by-step working shown at every stage.
The calculator checks your inputs against the triangle inequality before solving, so invalid triangles are caught immediately with a clear explanation rather than a broken calculation. Area and perimeter are computed automatically, and a scaled diagram illustrates the result.
Whether you're checking homework or solving a real-world triangulation problem, get accurate results with the reasoning shown, not just a bare number. No sign-up, no downloads required.