Triangle Calculator
Solve a triangle from three side lengths: area, perimeter, and all three angles.
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How to use Triangle Calculator
Three sides determine the triangle. A scaled form of Heron’s formula gives area, and the cosine rule gives the angles opposite sides a, b, and c.
- Enter side a, side b, side c.
- Check that the input follows the stated limits and uses consistent units.
- Run the calculator, review the result, then copy or download it.
Good to know
- Side lengths must be positive, use the same unit, and satisfy the strict triangle inequality. Nearly degenerate triangles may lose angle precision.
- Decimal inputs have at most 120 characters and magnitude from 1e-100 to 1e15, or zero. Floating-point results are rounded to 12 significant digits; extreme derived results may underflow or be rejected. Exact integer results are identified separately.
Common questions
What calculation does Triangle Calculator perform?
Three sides determine the triangle. A scaled form of Heron’s formula gives area, and the cosine rule gives the angles opposite sides a, b, and c.
What units are used for area?
If the side lengths are in meters, area is in square meters. Angles are displayed in degrees.
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