Triangle Calculator
Area and perimeter of a triangle from its sides
Use this when you need a fast, accurate result — no sign-up, works entirely in your browser.
Area (Heron)—
Perimeter—
Triangle type—
How to Use
- Enter your details into the fields above.
- Click the calculate button to get your result instantly.
- Use the clear button to start a new calculation.
Example
- Sides a = 3, b = 4, c = 5 → Area = 6, perimeter = 12, scalene right triangle
- Sides a = 5, b = 5, c = 6 → Area = 12, perimeter = 16, isosceles triangle
Formula
Area = √(s(s − a)(s − b)(s − c)) with s = (a + b + c) ÷ 2 (Heron's formula). Perimeter = a + b + c. Any two sides must add up to more than the third side.
About Triangle Calculator
Area and perimeter of a triangle from its sides. This free online tool gives you fast, accurate results without registration or downloads.
Everything runs locally in your browser, so your data is never uploaded or stored — privacy first.
Frequently Asked Questions
Is this tool free to use? +
Yes, it is completely free with no registration or download required.
Is my data private? +
Yes. Everything is processed locally in your browser. Nothing is uploaded or stored on our servers.
Does it work on mobile? +
Yes, it works on any device — phone, tablet, or desktop.