Round Pen Calculator
Our round pen calculator helps you calculate the round pen size you need based on the diameter or circumference of the designated land. This tool determines how many round pen panels you need based on your desired panel length.
This article briefly discusses how to build a round pen. More importantly, it focuses on how many round pen panels you need based on the required size of the pen.
How to build a round pen
Here's an overview of how we can build a round pen:

Measurements
Choose your pen's appropriate diameter and height based on the animals you wish to keep.
For example, if you plan to train a horse, you should have a round pen at least 60 feet in diameter.

Preparations
Make sure to build the pen on firm ground that isn't prone to flooding. Clean and level the land before installing the enclosure. Keeping in mind the safety and comfort of the animal, have suitable amounts of sand, wood shavings or soft dirt for the ground, and cement for fixing posts.

Steel or wood
Decide between steel or wood for the pen. Wood may be more economical, but you cannot move it once fixed. In comparison, steel may be more expensive but easier to assemble and more manageable for increasing or decreasing the size of the pen.
🔎 To learn about different types of steel and their weight, check out our steel weight calculator.

Panels and posts
Determine the required number of posts and panels based on your preferred panel lengths and pen size. The number of posts will be a multiple of the number of panels.
You can calculate your round pen panel quantity using our given calculator.

Installation
Starting from the entrance, mark the ground for posts. Dig the holes about 2 feet deep. Attach the panels to the posts and fix the posts in the ground using cement.
Once you've attached the gate, you're ready to bring the animals in.
How to use the round pen calculator
Here's how you can use our round pen calculator:

Enter your preferred pen diameter, e.g., 80 ft.

The calculator will give you the pen circumference of 251.3 ft.
🔎 Alternatively, you can also enter the pen's circumference in our calculator to obtain its diameter or use our circumference to diameter conversion calculator.
 Enter your preferred panel length. A typical panel size is 8 feet.
💡 Depending on the requirement, a standard round pen's panel length can be anywhere between 4 and 20 feet wide.
 Once you enter your preferred panel length, you'll get the number of panels required to build this round pen, which in this case is 31 panels.
How to manually calculate the round pen size
You can manually calculate your round pen panels quantity using the following formula:
 $P = D \times \pi \div L$
where:
 $P$ – Number of panels required to build the round pen;
 $D$ – Diameter of the round pen;
 $\pi$ – Math constant with a value of 3.1416 approx.; and
 $L$ – Preferred length of the panel.
Here's an example of calculating the required number of panels for a round pen, where the pen's diameter should be 100 feet and our preferred panel length is 15 feet.
Placing the values in the formula, we get:
 $P = 100 \times \pi \div 15 ≈ 21$
Thus, we require 21 panels of 15 feet each for building a round pen of 100 feet in diameter.
FAQ
For a round pen, how many 12 foot panels do I need?
16. That's how many 12foot round pen panels you need for a standard round pen with a diameter of 60 feet.
You can calculate the round pen panels that are required by using this formula:
Number of panels = Pen diameter × π / Preferred panel length
.
How big are round pens for horses?
A round pen with a diameter of 60 feet and a height of 5 feet is sufficient for keeping regular horses. For riding and training wild horses, such as stallions, a round pen of about 80 feet in diameter and a height of 6 feet is more suitable.
How do I calculate the number of panels for a round pen?
To calculate the number of panels for a round pen:
 Measure the diameter of your pen in feet. As an example, let's say it's 45 ft.
 Multiply the result by π to find its circumference, e.g.,
45 × 3.1416 = 141.4 ft
.  Divide the circumference by your desired panel length (in feet). So that's
141.4 / 12 = 12
.  Thus, with a 45 feet diameter, you'll need 12 panels, each 12 feet long.
How many 10′ panels in a 50′ round pen?
16. That's how many round pen panels you need for a round pen of 50′ diameter.
You can calculate the number of panels using the following formula:
Number of panels = Pen diameter × π / Preferred panel length
.