Solve any triangle by entering 3 known values (at least one side). Calculates all sides, angles, area, perimeter, heights, medians, inradius, circumradius, and vertex coordinates.
SSSSASASAAASSSADegree & Radian
How to use this calculator Enter any 3 values (at least one side length). Leave the unknowns blank and click Calculate. Supports Degree and Radian modes. For radian input, you can type expressions like pi/3.
Triangle Calculator
Provide 3 values including at least one side
°
°
°
Angle Unit:
Results are computed using trigonometric laws (Law of Cosines, Law of Sines).
Triangle Facts & Laws
Interior angles always sum to 180°. The exterior angle equals the sum of the two non-adjacent interior angles.
Triangle inequality: The sum of any two sides must be greater than the third side.
Pythagorean theorem (right triangles only): a² + b² = c², where c is the hypotenuse.
Law of Sines: a/sin(A) = b/sin(B) = c/sin(C). Useful when an angle and its opposite side are known.
Law of Cosines: a² = b² + c² − 2bc·cos(A). Generalizes the Pythagorean theorem to all triangles.
Heron's Formula (area from three sides): Area = √[s(s−a)(s−b)(s−c)], where s = (a+b+c)/2.