Plan 10 sq ft of run per laying hen, which is the outdoor figure in Virginia Cooperative Extension’s housing table and on the national poultry extension site; an older Virginia Tech table said 8. For 20 chickens that is 200 sq ft, or 160 at the old figure. Bantams run 5 to 8 sq ft each. Enter your flock below (our chicken run plans show every build) and the calculator returns the run area, then the hardware cloth, posts and sand to build it.
The inputs and the one number that matters
The calculator asks for your hen count, bantam or standard, and how generous you want to be: minimum (8), extension standard (10), or generous. Generous is 12 to 20 sq ft a hen for flocks whose run is their only outdoor space. That band is the range in our run design guide, our recommendation and not an extension finding; we could not find a published figure for permanently confined hens and say so. Bantams use 5 to 8 from Virginia’s table.
Here is the arithmetic for common flocks, so you can read the answer without the tool.
| Hens | At 8 | At 10 | At 12 | At 20 |
|---|---|---|---|---|
| 3 | 24 | 30 | 36 | 60 |
| 4 | 32 | 40 | 48 | 80 |
| 6 | 48 | 60 | 72 | 120 |
| 10 | 80 | 100 | 120 | 200 |
| 12 | 96 | 120 | 144 | 240 |
| 20 | 160 | 200 | 240 | 400 |
| 25 | 200 | 250 | 300 | 500 |
| 30 | 240 | 300 | 360 | 600 |
All figures are sq ft. A 12-hen flock at the extension standard wants 120 sq ft, which is a 10x12 run, or our 8x16 run at 128.
Run size for 20 chickens, and for six
Twenty hens at 10 is 200 sq ft, which is exactly our 10x20 run (10 by 20 feet, $1,900 to $2,450, 30 to 40 hours). Go generous and the number is 240 to 400, which is bigger than any plan we draw. Six hens at 10 is 60 sq ft, and at the generous band 72 to 120; our 6x8 run at 48 sq ft covers 4 hens at the extension standard and 6 at the older 8.
That is worth noticing: our own run plans are rated for more hens than the 10 sq ft rule gives. The 6x8 is rated for 6 to 9 hens, the 8x16 for 16 to 25 and the 10x20 for 25 to 40, which works out to 5 to 8 sq ft a bird. Read those ratings as a supplement to a coop’s attached run or to free-ranging, not as a full-time home.
| Run | Area | Hens at 10 | Hens at 8 | Materials | Per sq ft |
|---|---|---|---|---|---|
| 6x8 | 48 | 4 | 6 | $850-$1,100 | $17.71-$22.92 |
| 8x16 | 128 | 12 | 16 | $1,300-$1,700 | $10.16-$13.28 |
| 10x20 | 200 | 20 | 25 | $1,900-$2,450 | $9.50-$12.25 |
Cost per sq ft falls about 46% between the smallest and largest, so if you will outgrow a run, build the bigger one once.
What the calculator builds from the area
Once it has square feet, it works out materials with formulas we checked against our own runs. Wall cloth is the exposed perimeter times wall height divided by the 3-ft width of a 36-in roll, plus a lap allowance. Roof cloth is the area divided by 3 plus the same allowance. The apron is 2 ft wide, 12 in down and 12 in out, so it is the full perimeter times two thirds. Posts are one per 4 ft of exposed perimeter, rounded up. Sand is 4 in deep, in cubic yards.
Run those on the 10x20 and the answers match the plan line for line: 135 lin ft of wall cloth, 75 of roof cloth, 40 of apron, 3 cu yd of sand. The 6x8 and 8x16 match too (63 and 108, 18 and 48, 19 and 32). The lap allowance in those plans is exactly 12.5%; the 8x12’s attached run uses none, which is why the tool offers both. Posts are the one place the rule is a floor: the 10x20 plan sets 18 plus two centre posts where the rule says 16.
Covered run sizing
A roof does not change how many square feet a hen needs. It changes what holds the roof up. Our standalone runs are 8 ft wide or less with purlins only; at 10 ft wide the plan adds a centre beam on two 90-1/2 in posts, because 1/4-in mesh spanning 10 ft sags into a hammock. Covered also adds the roof cloth above, and our plans add a shade cloth panel of about one third of the floor area (16, 43 and 67 sq ft on the three runs).
A solid roof is a different build. At our 24 in of coverage per panel and 10-ft sheets, 20 sq ft each, a 10x20 needs 10 panels. Pitch and purlin rules for metal are in the chicken coop roof guide.
Where run size goes wrong
Square feet is not the same as usable space. Our plans grade the run to drop an inch every 8 ft and finish it 3 to 4 in deep in coarse sand or 3/8-in drain rock, because a ponded run turns to mud. A big muddy run is worse than a small dry one. The hardware cloth guide covers the mesh itself.