The ring is sized by the empty part
Work out the ground an agility course occupies and the answer comes out surprisingly small. Eighteen obstacles at twenty feet of spacing is seventeen gaps, 340 feet of path. Fold that into a rectangle sixty feet wide with the legs twenty feet apart and you get three passes, so the rectangle is 113 by 60 feet — about 6,800 square feet, roughly a sixth of an acre.
Then add the run-off. Twenty feet on each of the four sides turns 113.3 by 60 into 153.3 by 100, which is 15,333 square feet. The obstacles did not move and the path did not get longer. The ring more than doubled because of the band around the outside, and that band is 8,533 square feet — 55.7 percent of everything you have to rent, level, fence, drag and mow.
This is the number that catches people out when they price a venue or a build. The run-off is not a margin of error on the course; it is the majority of the site. Five more feet all round on that same example adds another 2,633 square feet and 40 more feet of perimeter fencing. Five feet.
Folding, and why width shortens a ring faster than anything else
A course path is a single line, and a ring is a rectangle, so somewhere the line has to double back on itself. How many times it can double back is set by the width divided by how far apart you are willing to run two adjacent legs. Sixty feet at twenty feet between legs gives three passes; eighty feet gives four.
The effect on length is not gradual — it steps. At three passes the 340 foot path needs 113 feet of length. At four passes it needs 85. At two it needs 170. Nothing in between exists, because you cannot have three and a half passes. If a site is 20 feet too short, widening the working rectangle by one pass width is usually the cheaper fix than finding more length, and the calculator will show you the step.
| Working width | Passes at 20 ft | Length for 340 ft of path | Ring at 20 ft run-off | Ring area |
|---|---|---|---|---|
| 40 ft | 2 | 170.0 ft | 210 x 80 ft | 16,800 sq ft |
| 60 ft | 3 | 113.3 ft | 153 x 100 ft | 15,333 sq ft |
| 80 ft | 4 | 85.0 ft | 125 x 120 ft | 15,000 sq ft |
| 100 ft | 5 | 68.0 ft | 108 x 140 ft | 15,120 sq ft |
Notice how flat the area column is. Total ring area barely moves across that whole range, because the path length is fixed and you are only choosing what shape to wrap it in. What changes dramatically is the aspect ratio, and therefore whether it fits the piece of ground you actually have. The area is decided by the course; the shape is decided by you.
What this model is and is not
Folding a path into even passes is a planning approximation, not a course. Real courses turn, cross themselves, use the same ground twice and put obstacles at angles, and a course designer works to a set of rules this page does not have. What the fold gives you is a defensible first number for the footprint, built from inputs you chose rather than from constants somebody invented.
It is deliberately straight-line too. The distance between two obstacles measured obstacle to obstacle is shorter than the line anything actually travels between them, which is why the course yardage calculator exists separately and adds the arc a wider line takes.
Where this hands off
The perimeter this page produces is what the fencing pages consume: chain link fence material for fabric, posts, rails and fittings, or modular panel layout if the boundary is panels rather than a permanent fence. Surfacing the ground inside it is the arena footing calculator, which does depth, cubic yards, tons and truck loads for sand, screenings, fibre and rubber blends and is a better tool than anything this page could add. If the ring is a hard pad rather than footing, backyard court size covers playing area plus run-off on a pour, and site layout squaring proves the rectangle is square before anything goes in the ground.
Questions people ask
What spacing should I use between obstacles?
This page will not tell you, and you should be suspicious of any page that does. Spacing is set by the rule book of the organization you compete under, it differs between organizations, it differs between classes within one organization, and it changes. Get the figure from the current rule book or from a course designer in your club, then type it in. The arithmetic here is about what your figure does to the footprint, not about what the figure should be.
How much run-off should I leave around the course?
Also your number, from the same sources. What the calculator can do is show you what the choice costs: on an eighteen obstacle course folded three passes into sixty feet, twenty feet of run-off is 8,533 square feet and 55.7 percent of the whole ring, and at that point every extra foot adds about 511 more square feet and 8 more feet of perimeter. Seeing that trade priced usually changes the conversation from a number people argue about to a budget people decide.
Why does the ring barely change size when I change the width?
Because you are wrapping a fixed length of path in a different shape rather than shortening it. Doubling the working width roughly halves the working length, so the working area stays put. The ring area moves a little because the run-off band changes shape, and it is smallest when the ring is closest to square. What the width really decides is whether the ring fits your ground, which is why the optional length and width fields are there.
Does this account for the space obstacles themselves take up?
Only through the spacing you enter, which is measured obstacle to obstacle and therefore already contains them. It does not know that a tunnel is fifteen feet of ground and a jump is four, and it does not need to for a footprint estimate. If a particular long obstacle is what is binding your layout, add its length into the spacing on either side of it rather than trying to model it separately.
Can I use this for a practice field in the back yard?
That is probably where it is most useful, because a back yard is the case where the ground is fixed and everything else has to bend. Enter the length and width you have in the optional fields and the page tells you either how much is left over or, if it does not fit, the largest run-off that ground would allow at your working rectangle. That last number is often the honest answer: not how big a ring you want, but what the yard will actually carry.