Enter three values
Fill in any three sides or angles — sides a, b, c line up with the opposite angles A, B, C.
Triangle Solver
Enter any three sides or angles — with at least one side — and solve every missing measurement instantly.
Fill in exactly three fields (at least one side), leave the rest blank.
Sides (opposite each matching angle)
Angles (degrees)
–Side a
–Side b
–Side c
–Angle A
–Angle B
–Angle C
–Area
–Perimeter
How it works
Automatic case detection
The solver detects SSS, SAS, ASA, AAS or SSA and applies the right formula automatically.
Get every measurement
See every missing side, every missing angle, the area and the perimeter at once.
FAQ
How many values do I need to solve a triangle?
You need exactly three known values, and at least one must be a side length. Three angles alone only fix the triangle's shape, not its size.
What is the ambiguous SSA case?
When you know two sides and a non-included angle (SSA), there can be zero, one or two valid triangles. This tool returns one valid solution and flags when a second solution also exists.
Which formulas does this tool use?
It uses the law of cosines (c² = a² + b² − 2ab·cos C) to relate three sides and an angle, and the law of sines (a/sin A = b/sin B = c/sin C) to relate sides and their opposite angles.