Heron’s Formula Calculator
⬛ Area & perimeter (2D). Use the Heron’s formula formula to find area, side a, side b, side c: pick the value you want, type the others, and the answer updates as you go.
The area of a triangle from its three sides.
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| Area | cm² |
| Side a | cm |
| Side b | cm |
| Side c | cm |
Worked example
Find the area when Side a = 3 cm, Side b = 4 cm, Side c = 5 cm.
Using A = √(s(s-a)(s-b)(s-c)), s = (a+b+c)/2: Area = 6 cm².
Frequently asked questions
What is the formula for Heron’s formula?
A = √(s(s-a)(s-b)(s-c)), s = (a+b+c)/2. The area of a triangle from its three sides.
What do the letters stand for, and what units are used?
Area in cm², Side a in cm, Side b in cm, Side c in cm.
How do you calculate area?
Put the values into A = √(s(s-a)(s-b)(s-c)), s = (a+b+c)/2. For example, with Side a = 3 cm, Side b = 4 cm, Side c = 5 cm, area = 6 cm².
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (area, side a, side b, side c) and fill in the others: it rearranges the formula for you.
