Triangle Calculator
Calculate triangle area with Heron formula. Identifies equilateral, isosceles, scalene, right.
How to Use
Enter your values in the fields above and click Calculate to get instant results. All computations run locally in your browser. No data is ever uploaded or stored.
Related Calculators
Triangle Geometry Calculations
CalcSolver's triangle calculator determines area, perimeter, and all three angles from known side lengths. It uses the Law of Cosines to find angles and Heron's formula for area: Area = √(s(s-a)(s-b)(s-c)) where s is the semi-perimeter.
For a triangle with sides 3, 4, 5 (a classic right triangle): area = 6, perimeter = 12, and angles are 36.87°, 53.13°, and 90°. The Pythagorean theorem confirms right triangles: if a² + b² = c², the angle opposite the longest side is exactly 90°.
Triangle types: equilateral (all sides equal, all angles 60°), isosceles (two sides equal), right (one 90° angle), obtuse (one angle > 90°), and acute (all angles < 90°). The sum of interior angles is always 180°. Use CalcSolver's circle calculator for circular geometry and scientific calculator for trigonometric functions.
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Frequently Asked Questions
How do I find the area of a triangle?
The most common formula is A = ½ × base × height. If you know all three sides, use Heron's formula: A = √(s(s-a)(s-b)(s-c)), where s is the semi-perimeter (a+b+c)/2.
How do I find an unknown side?
Using the Pythagorean theorem for right triangles: a² + b² = c². For non-right triangles, use the law of cosines: c² = a² + b² − 2ab×cos(C).
What are the types of triangles?
By sides: equilateral (all equal), isosceles (two equal), scalene (all different). By angles: acute (all < 90°), right (one = 90°), obtuse (one > 90°).