Triangle Solver
Solve any triangle from sides and angles.
How to use
- 1 Enter the values you know — at least three, including one side.
- 2 Leave the unknown sides or angles blank.
- 3 Read the full solution: sides, angles, area and perimeter.
- 4 Copy the result if you need it elsewhere.
About Triangle Solver
The Triangle Solver finds every missing measurement of a triangle once you give it enough information.
Supply three known values — including at least one side — and it returns all three side lengths, all three angles, the area and the perimeter.
It recognises the four classic solvable cases: SSS (three sides), SAS (two sides and the included angle), ASA (two angles and the side between them) and AAS (two angles and a non-included side).
Behind the scenes it applies the law of cosines to recover angles from three sides or to find the third side from two sides and their included angle, and the law of sines to scale the remaining sides once the angles are known.
The area is computed with Heron’s formula, so it works for any triangle, not just right-angled ones.
The solver also checks that your inputs can actually form a triangle — flagging cases where the sides violate the triangle inequality or where two angles already add up to 180 degrees or more.
Just type the values you know and leave the unknown boxes blank; the result updates live.
As with every My Tools Garage tool, all the trigonometry runs locally in your browser, with nothing uploaded, so it is fast, private and available offline.
FAQ
What combinations can it solve?
It solves SSS, SAS, ASA and AAS. You must provide three values in total, and at least one of them must be a side length.
Are angles in degrees or radians?
All angles are entered and reported in degrees.
What if my values can’t form a triangle?
The solver checks the triangle inequality and angle sums, and shows a clear message when no valid triangle exists.