Triangle Solver
Give it SSS, SAS, ASA, or AAS — get every side, every angle, area, perimeter, and a true-to-scale diagram.
Notation: side a is opposite angle A, side b opposite B, side c opposite C.
Method:
Diagram
Gold labels mark the values you entered.
Steps
How to use the triangle solver
- Pick what you know. SSS, SAS, ASA, or AAS — the inputs change to match.
- Enter the values. Use the standard notation: side a opposite angle A, and so on.
- Press Solve triangle. You get all three sides, all three angles, area, and perimeter.
- Check the diagram and steps. Gold labels show your inputs; the steps show the law used at each stage.
Frequently asked questions
What do SSS, SAS, ASA, and AAS mean?
They describe which three values you know. SSS = three sides; SAS = two sides and the angle between them; ASA = two angles and the side between them; AAS = two angles and a side that isn't between them.
Why does the triangle inequality matter?
If one side is longer than the other two put together, the ends can't meet and no triangle exists. The solver checks this before solving and tells you when the sides are impossible.
Which side is "a"?
Standard notation: side a sits opposite vertex A, side b opposite B, and side c opposite C. The diagram labels every side and angle so you can check.
How is the area calculated?
With Heron's formula from the three sides: area = √(s(s−a)(s−b)(s−c)), where s = (a+b+c)/2 is the semi-perimeter.
Can it solve ambiguous SSA cases?
No — SSA (two sides and a non-included angle) can produce zero, one, or two valid triangles, so this tool sticks to the four unambiguous cases: SSS, SAS, ASA, and AAS.
Is this accurate enough for homework?
Angles are computed to full floating-point precision and displayed to two decimals — plenty for classwork. Always double-check against your teacher's notation for which side is which.
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Open tool →Support the codex
This tool is free, with no account and no ads. If it saved you some time, consider supporting the indie dev behind it.