Triangle Calculator
Solve a triangle from three sides, two sides and the included angle, or a right triangle. Returns missing sides/angles, area, perimeter, and inradius.
Sides
Angles (°)
Measurements
How to use
- 1
Pick the inputs you have. Three sides (SSS), two sides and the angle between them (SAS), or two legs of a right triangle.
- 2
Enter the values. Angles are in degrees.
- 3
The calculator returns the missing sides and angles, plus area, perimeter, and inradius.
Frequently asked questions
For any triangle, the sum of any two sides must be greater than the third. If a = 1, b = 2, c = 10, no triangle exists — sides 1 and 2 together can't reach the endpoints of side 10.
Law of cosines to find each angle from the three sides, then Heron's formula for the area. Both are textbook standard.
The inradius is the radius of the largest circle that fits inside the triangle, tangent to all three sides. Formula: area / semi-perimeter, where semi-perimeter is half the sum of the three sides.
SSA is the ambiguous case — it can have zero, one, or two valid triangle solutions depending on the values. This calculator covers SSS, SAS, and right triangles, which all have unique solutions. For SSA, sketch the configuration first to see how many triangles exist.
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Source: Law of cosines, law of sines, Heron's formula · Last verified 2026-06. This tool provides estimates only and is not legal, tax or financial advice. Always verify your specific situation with the relevant UAE authority or a licensed advisor before taking action.