Round Pen Calculator: Panels, Circumference and Area

This calculator works out the materials for a round pen. Enter the diameter you want and the length of one panel; you get the fence length around the pen, the number of panels to buy and the area inside.

Formula

Circumference = π × diameter. Panels = circumference ÷ panel length, rounded up. Area = π × (diameter ÷ 2)².

• dia: inside diameter of the pen
• pl: length of one panel as sold (gate panels count as panels)

Worked Example

A 60 ft pen with 12 ft panels.

1. Circumference = π × 60 = 188.5 ft
2. Panels = 188.5 ÷ 12 = 15.7, rounded up to 16 panels
3. Area = π × 30² = 2,827 ft²

How to read the result

Panels make a polygon, not a true circle, so a pen of whole panels comes out a little different from the diameter you entered. With 16 panels of 12 ft, the pen is about 61 ft across. Choose the diameter that suits the work you plan with the horse; many trainers use 50 to 60 ft.

Limits and common mistakes

• Add the gate as one of the panels, or subtract its width if it is separate.
• Leave room outside the pen for access and drainage.

Frequently Asked Questions

How many 12 ft panels for a 50 ft round pen?

14 panels (π × 50 ÷ 12 = 13.1, rounded up).

How many panels for a 60 ft pen?

16 panels of 12 ft.

What is the area of a 60 ft round pen?

About 2,827 ft².

Does a gate count as a panel?

Usually yes, if it is the same length.

in dia | Pen diameter | ft | 60 | 1 | 1000
in pl | Length of one panel | ft | 12 | 1 | 100
out circ | Fence length (circumference) | ft | pi * dia | 1
out panels | Panels to buy | panels | ceil(round(pi * dia / pl, 6)) | 0
out area | Area inside | ft² | pi * (dia / 2)^2 | 0