Horse trainers and other livestock owners use round pens for the convenient and temporary confinement of animals. Made with prefabricated, solid or open panels, round pens can be assembled to create any needed size. The size that your round pen needs to be depends on what you are using it for. Once you determine the necessary pen size, the number of panels that you need to create that size can be calculated with a simple mathematical formula.
Determine what diameter your pen needs to be. For basic horse training, the average size is 60 feet in diameter. If you are quarantining larger numbers of horses or other livestock like cattle, you may want a pen that is 90 to 120 feet in diameter. If you are working with small livestock, such as hogs or sheep, you might not need anything bigger than 30 or 40 feet in diameter. For infant or very small animals you may only need five to 10 feet in diameter.
Consider what height the pen needs to be. Pen panels come in heights ranging from two feet to five feet. A short pen is appropriate for small or infant animals, such as lambs, piglets or even puppies. If the animals are jumpers or climbers, use a medium to large height. Use medium height pen panels for medium to larger size tame or mellow livestock, like hogs, sheep or goats. Use a four- or five-foot height for tame horses. Wild horses will need the highest pen, as they can easily clear shorter heights.
Decide what length of individual pen panels will suit you best. Panels come in a variety of lengths, from eight to 16 feet. Shorter panels weigh less and are easier to transport; however more of them will be required to make up the pen, thus extending the time it takes to set the pen up.
Calculate the number of panels you need to make up your determined pen diameter. Multiply the diameter by 3.14 to find the circumference. Divide the circumference by the panel length to determine the requisite number of panels.