Heron's Formula Table: Triangle area by Side a
Reference table of triangle area for Heron's Formula across a range of side a values — exact, engine-computed figures you can read off at a glance.
Heron's Formula Calculator
Verified formula Updated Jun 2026 Private — runs on your device
Verified formula
Private
Triangle area
6.0000
- Perimeter
- 12.00
For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.
How to use the Heron's Formula Calculator
The Heron's Formula Calculator works out your triangle area, along with 1 related figure in an instant. Enter side a, side b and side c and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.
- Enter the side a.
- Enter the side b.
- Enter the side c.
- Read off your triangle area, together with perimeter — the calculator updates automatically, with no button to press.
Formula
The Heron's Formula Calculator uses the formula:
Triangle area = √((Side a + Side b + Side c) ÷ 2 × ((Side a + Side b + Side c) ÷ 2 - Side a) × ((Side a + Side b + Side c) ÷ 2 - Side b) × ((Side a + Side b + Side c) ÷ 2 - Side c))
Worked example
For example, with side a of 3, side b of 4 and side c of 5, the triangle area is 6.0000.
| Side a | 3 |
|---|---|
| Side b | 4 |
| Side c | 5 |
| Triangle area | 6.0000 |
|---|---|
| Perimeter | 12.00 |
Results are estimates for educational use, not professional advice.
Key terms explained
- Perimeter
- The total distance around the outside of a two-dimensional shape.
- Area
- The amount of two-dimensional space a shape covers, measured in square units.
Frequently asked questions
It finds a triangle's area from its three sides. With semi-perimeter s, area = √(s(s−a)(s−b)(s−c)). A 3-4-5 triangle has area 6.
It is half the perimeter: (a + b + c) ÷ 2. Heron's formula uses it as the base of the calculation.
When you know all three sides but not the height, so the usual half-base-times-height formula is hard to apply.
Yes. Any side must be shorter than the sum of the other two, or the shape is not a valid triangle.
Enter the side a. Enter the side b. Enter the side c. Read off your triangle area, together with perimeter — the calculator updates automatically, with no button to press.
Related guides
How to Calculate Heron's Formula: Formula, Steps & Examples
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