MATH & NUMBERS
Triangle Calculator
Solve a triangle from three sides — angles, area and perimeter.
100% free
No sign-up
Private — runs in your browser
Instant results
KEY TAKEAWAYS
- Solve a triangle from three sides — angles, area and perimeter.
- Free to use — no sign-up, no account and no usage limits.
- Runs entirely in your browser, so the numbers you enter stay private.
- Works on desktop and mobile with instant, accurate results.
Last updated: June 2026
About the Triangle Calculator
Enter the three side lengths to get every interior angle (law of cosines), the area (Heron's formula), the perimeter and the triangle type.
Frequently asked questions
What if the sides can't form a triangle?
The tool checks the triangle inequality and tells you if no triangle is possible.
Free online tool from ConvertFleet. Calculations run entirely in your browser — nothing you type is sent anywhere. Results are estimates for general guidance only.