Triangle Calculator
Solve any triangle from the information you have. Choose the combination of sides and angles you know — SSS, SAS, ASA, AAS or SSA — and the calculator returns all remaining sides, angles, area and perimeter.
Enter the values you know
Enter values and press Solve.
Triangles and the rules used
Angle sum
A + B + C = 180°
Law of Sines
a / sin A = b / sin B = c / sin C
Law of Cosines
c² = a² + b² − 2ab · cos C
Area (Heron's formula)
Area = √[s(s − a)(s − b)(s − c)] where s = (a + b + c) / 2
Area (from sides and included angle)
Area = ½ · a · b · sin C
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Frequently asked questions
You need at least three pieces of information, including at least one side. The valid combinations are SSS, SAS, ASA and AAS. SSA is ambiguous — it may produce 0, 1 or 2 possible triangles.
Because the law of sines may produce two possible values for an angle (θ and 180° − θ). Depending on the side lengths, both can produce valid triangles. This calculator returns the primary solution; disambiguate manually if needed.
Yes — this calculator handles all valid triangles: acute, right, obtuse, scalene, isosceles and equilateral. The classification is reported in the results.