Triangle Calculator
Enter three known measurements and solve the whole triangle: sides, angles, perimeter and area.
Runs 100% in your browser — nothing is uploaded.
Result
Formula
Law of cosines: c² = a² + b² − 2ab·cos C · Heron: A = √(s(s−a)(s−b)(s−c))
About this calculator
Solve any triangle when three independent measurements are known: three sides (SSS), two sides and the included angle (SAS), or two angles and the included side (ASA). The calculator returns all side lengths, all interior angles, the perimeter, and the area. The calculator uses standard trigonometric relationships.
How to use
- 1
Select your known measurements: 3 sides (SSS), 2 sides + angle (SAS), or 2 angles + side (ASA).
- 2
Enter the values for the labeled sides and angles (e.g., Side a, Side b, Included angle C).
- 3
Click Calculate to see all sides, angles, perimeter, and area.
Frequently asked questions
Why is there no side-side-angle mode?
SSA can produce zero, one or two triangles (the ambiguous case); SSS, SAS and ASA give unambiguous answers.
Please note: Results are estimates for general information only and are not professional or medical/financial advice.