Triangle Calculator
Solve any triangle from three sides or two sides and the angle between.
Area (Heron's formula)
31.305
Angles
35.4°, 48.2°, 96.4°
Perimeter
28
Two laws solve everything
The law of cosines (c² = a² + b² − 2ab·cos C) handles SSS and SAS cases; the law of sines handles the rest. Heron's formula computes area straight from three sides via the semi-perimeter — no heights needed.
The triangle inequality
Three lengths form a triangle only if each is shorter than the other two combined — 3, 4, and 12 can't close. The calculator checks this first, because the law of cosines silently produces impossible angles otherwise.
Frequently asked questions
- How does the Triangle Calculator work?
- Solve any triangle from three sides or two sides and the angle between.
- Is the Triangle Calculator free to use?
- Yes. The Triangle Calculator is completely free, runs entirely in your browser, and requires no account or sign-up. Your inputs never leave your device.
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