Solve a triangle from three sides: Heron area, perimeter, all three interior angles, and equilateral/isosceles/scalene type.. Triangle Solver (SSS) is a free online tool from the ToolsRift Math Calculators collection. It runs entirely in your browser — nothing to install, no signup, and your data never leaves your device.
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How to use Triangle Solver (SSS)
Enter the three side lengths and the solver returns the area, perimeter, all three interior angles and whether it is scalene, isosceles or equilateral.
Frequently asked questions
What is SSS solving?
Side-Side-Side: given all three side lengths, the calculator determines the angles, area, perimeter and classification.
How is the area found from three sides?
With Heron's formula: area = √(s(s−a)(s−b)(s−c)), where s is the semi-perimeter (a+b+c)/2.
How are the angles calculated?
Using the law of cosines, e.g. cos(A) = (b²+c²−a²)/(2bc), for each of the three interior angles.
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