Find the missing pieces.
Start with what you know. We’ll draw your triangle and walk through the rest.
What do you know?
Each side must be shorter than the other two combined.
Follow the calculation
Triangle solver questions
Wondering about the why? Start here.
How do I find a missing angle in a triangle?
If you know two interior angles, subtract their sum from 180°. For example, angles of 50° and 60° leave 70°. If you know side lengths instead, choose a supported solver mode to calculate the angles using the sine or cosine rule.
Understand the cosine ruleWhat information do I need to solve a triangle?
Use SSS for three sides, SAS for two sides and the angle between them, or AAS for two angles and a side. SSA uses two sides and an angle opposite one of them and may have zero, one, or two solutions. All lengths must use the same unit.
Understand the sine ruleWhy does the solver sometimes show two triangles?
In the ambiguous SSA case, the known measurements may fit two different triangles. An acute angle and its supplementary obtuse angle have the same sine. The solver shows both solutions when both satisfy the supplied measurements.
Explore the ambiguous case