About the Perimeter Calculator
Perimeter of a rectangle, triangle, circle or polygon, with the fencing needed.
Also known as: perimeter of a shape, fence length calculator, boundary length, circumference perimeter.
How to use this calculator
- Enter shape, fence post spacing and the other fields.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
Rectangle P = 2(l + w) · Circle P = 2πr
Worked example
Using the values pre-filled in the calculator above:
- Shape: Rectangle
- Length = 20 m
- Width = 15 m
- Fence post spacing = 2.4 m
the calculator returns:
- Perimeter: 70 m
- In feet: 229.66
- In yards: 76.553
- Fence posts needed: 31