Triangle Area Calculator
Fill in the values and the answer updates as you type.
How the Triangle Area Calculator works
Heron's formula: area = √(s(s−a)(s−b)(s−c)), where s is half the perimeter. If the sides cannot form a triangle, no result is shown.
Inputs and results
The Triangle Area Calculator takes 3 inputs and gives 2 results.
What you enter
- Side a — starts at 3.
- Side b — starts at 4.
- Side c — starts at 5.
What you get
- Area
- Perimeter
Example: Triangle Area Calculator with the starting values
With side a 3, side b 4 and side c 5, the calculator returns:
| Area | 6 |
|---|---|
| Perimeter | 12 |
Change any value above and the results update straight away.
Triangle Area Calculator FAQ
How do I use the Triangle Area Calculator?
Enter side a, side b and side c in the fields, then read area and perimeter in the result panel. The answer updates as you type, and you can press Calculate or Enter to refresh it. Use “Copy link” to share your exact numbers with someone else.
What does the Triangle Area Calculator calculate?
Area and perimeter from three side lengths. It returns area and perimeter from the 3 values you provide.
What values does the Triangle Area Calculator start with?
It opens with side a 3, side b 4 and side c 5 so you can see a working result straight away. Replace them with your own numbers, or press Reset to return to these starting values.
Is the Triangle Area Calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so nothing you type is sent to or stored on our servers. See the Privacy Policy for details.
Can I rely on the Triangle Area Calculator for important decisions?
Treat the result as a well-rounded estimate. Real situations often have details a general calculator cannot know, so confirm important decisions with a qualified professional. See the Disclaimer for more.