Chicken coop measurements in our plans start at 4 sq ft of coop floor and 8 to 10 sq ft of run for a standard laying hen, so a flock of 12 wants a 48 sq ft coop and a 96 to 120 sq ft run. The chart below runs that arithmetic from 2 hens to 50 and matches each flock to the plans that carry it, using each plan’s own floor and rating.
Read the 4 as ours. Penn State lists 1.5 sq ft indoors for laying hens and 2 for large chickens, poultry.extension.org says 3 to 4, and Oregon State says at least 3 with a run. Our 4 is the top of that spread, not a legal minimum and not a universal standard. The chart shows where each plan lands against it.
The chart, 2 to 50 hens
| Hens | Coop floor at 4 sq ft | Run at 8-10 sq ft | Nest boxes, OSU / Penn State | Roost, 6-10 in a bird | Vent at our 1:10 (sq ft) | Our plans that carry it, cheapest first |
|---|---|---|---|---|---|---|
| 2 | 8 | 16-20 | 1 / 2 | 12-20 in | 0.8 | 4x8 A-frame tractor (10 sq ft), 4x4 starter (10 sq ft) |
| 3 | 12 | 24-30 | 1 / 2 | 18-30 in | 1.2 | 4x8 A-frame tractor (10 sq ft, short of the 12), 6x8 A-frame (15 sq ft) |
| 4 | 16 | 32-40 | 1 / 2 | 24-40 in | 1.6 | 6x10 tractor (19 sq ft), 6x8 A-frame (15 sq ft, short of the 16) |
| 6 | 24 | 48-60 | 2 / 3 | 36-60 in | 2.4 | 6x10 tractor (19 sq ft, short of the 24), 4x8 lean-to (23 sq ft, short of the 24) |
| 8 | 32 | 64-80 | 2 / 3 | 48-80 in | 3.2 | 6x8 coop (37 sq ft), 6x8 walk-in (37 sq ft) |
| 10 | 40 | 80-100 | 3 / 4 | 60-100 in | 4.0 | 6x8 walk-in (37 sq ft, short of the 40), 6x10 walk-in (47 sq ft) |
| 12 | 48 | 96-120 | 3 / 4 | 72-120 in | 4.8 | 6x10 walk-in (47 sq ft, short of the 48), 8x8 walk-in (51 sq ft) |
| 15 | 60 | 120-150 | 4 / 5 | 90-150 in | 6.0 | 8x12 coop (80 sq ft), 10x10 walk-in (84 sq ft), 8x12 walk-in (58 sq ft, short of the 60) |
| 20 | 80 | 160-200 | 5 / 6 | 120-200 in | 8.0 | 10x12 walk-in (74 sq ft, short of the 80), 8x16 walk-in (79 sq ft, short of the 80) |
| 25 | 100 | 200-250 | 7 / 8 | 150-250 in | 10.0 | 8x16 walk-in (79 sq ft, short of the 100) |
| 30 | 120 | 240-300 | 8 / 9 | 180-300 in | 12.0 | none yet, see below |
| 40 | 160 | 320-400 | 10 / 11 | 240-400 in | 16.0 | none yet, see below |
| 50 | 200 | 400-500 | 13 / 14 | 300-500 in | 20.0 | none yet, see below |
The coop floor and run columns are arithmetic. The nest boxes use two published rules: Oregon State’s one per four hens, and Penn State’s two for the first four and one for each four after that. Roost runs from Penn State’s 6 inches a bird to our 10. Vent at 1 sq ft per 10 of floor is our own design default, not a published number; each plan page lists its own vent area, and the ventilation guide explains the reasoning.
Where a plan’s floor falls short of 4 per bird it says so, and it falls short more often than the names suggest. The 8x16 walk-in is the only plan that reaches 25 hens, with 79 sq ft against the 100 that our default asks. Past 26 hens we have no single coop. The planned pages for 30 and 50 hens cover the split-flock options.
What each plan gives per bird at its ceiling
| Plan | Coop floor, sq ft | Rated | Floor per hen at the ceiling | Floor per hen at the bottom | Run per hen at the ceiling | Nest boxes |
|---|---|---|---|---|---|---|
| 4x4 starter | 10 | 2-3 | 3.3 | 5.0 | 5.3 | 2 |
| 4x8 A-frame tractor | 10 | 2-3 | 3.3 | 5.0 | 5.3 | 2 |
| 6x8 A-frame | 15 | 3-5 | 3.0 | 5.0 | 5.2 | 2 |
| 4x6 | 16 | 3-4 | 4.0 | 5.3 | 6.0 | 2 |
| 6x10 tractor | 19 | 4-6 | 3.2 | 4.8 | 5.5 | 2 |
| 4x8 shed | 23 | 4-6 | 3.8 | 5.8 | 5.3 | 2 |
| 4x8 lean-to | 23 | 4-6 | 3.8 | 5.8 | 5.3 | 2 |
| 6x8 coop | 37 | 6-9 | 4.1 | 6.2 | 5.3 | 3 |
| 6x8 walk-in | 37 | 7-10 | 3.7 | 5.3 | 6.0 | 3 |
| 6x10 walk-in | 47 | 9-12 | 3.9 | 5.2 | 6.0 | 3 |
| 8x8 walk-in | 51 | 10-13 | 3.9 | 5.1 | 6.2 | 4 |
| 8x12 walk-in | 58 | 14-18 | 3.2 | 4.1 | 7.1 | 5 |
| 8x10 walk-in | 66 | 12-14 | 4.7 | 5.5 | 6.9 | 4 |
| 10x12 walk-in | 74 | 18-22 | 3.4 | 4.1 | 7.3 | 6 |
| 8x16 walk-in | 79 | 19-26 | 3.0 | 4.2 | 6.2 | 7 |
| 8x12 coop | 80 | 12-19 | 4.2 | 6.7 | 5.1 | 5 |
| 10x10 walk-in | 84 | 15-17 | 4.9 | 5.6 | 7.1 | 5 |
At the ceiling, the 8x16 walk-in gives 3.0 sq ft a hen, the 6x8 A-frame 3.0, the 4x4 and the 4x8 tractor 3.3, and the 8x12 walk-in 3.2 (the pallet, modern and insulated variants share their parents’ floors and are left out of the table). Those clear Oregon State’s 3 and sit under our 4, so treat the first number in each plan’s range as the comfortable flock. The 8x10 walk-in and the 10x10 give 4.7 and 4.9, the most generous in the line.
Breed class and confinement
| Source and bird | Indoors, sq ft | Outdoor run, sq ft |
|---|---|---|
| Penn State, bantam chickens | 1 | 4 |
| Penn State, laying hens | 1.5 | 8 |
| Penn State, large chickens | 2 | 10 |
| poultry.extension.org, laying hens | 3-4 | 10 |
| OSU EC 1644, with a run | at least 3 | run figure not stated |
| OSU EC 1644, no outdoor access | 8-10 | none |
| Our plans’ default | 4 | 8 as the comfortable flock |
Oregon State’s 8 to 10 sq ft with no outdoor access is the figure that matters in a snowed-in winter, since it is roughly three times its own figure with a run. If your birds will be shut in for weeks, size from that row and read the cold climate plans. Penn State separates bantams, laying hens and “large chickens”, and none of the sources fetched for this page gives a figure by named breed, so a per-breed number beyond that is not printed here. For ducks, the duck house size calculator has its own figures.
How to use the 4, and when the run can shrink
Treat 4 sq ft as a design number you can defend, not a target to squeeze under. It sits above the published floors, and it is what the floor-per-bird column is measured against, so a plan that lands at 3.2 at its ceiling is not breaking a rule, it is telling you to stock at the lower end of its range. The run is where flexibility lives. Our plan text says 5.1 sq ft a hen in the 8x16 run works only if the flock is out on grass most of the day and uses the run to sleep, shelter and wait out weather. Shut the same birds in full time and the extension figures of 8 to 10 apply. Free-ranging is the one case where a smaller run is defensible, and none of the sources fetched for this page gives a smaller number for it, so we do not print one.
Other measurements
| Measurement | Published | Our plans use |
|---|---|---|
| Nest box size | 12 x 12 x 12 in (OSU), at least 12 x 12 in (Penn State) | Banks 17 in deep, about 15 in wide per box, hung outside with a hinged lid |
| Roost height | 2 ft (OSU), 18-24 in (Penn State) | Top of bar 20 in off the floor |
| Roost spacing | 10 in apart (OSU), 1 ft (Penn State) | 11-13/16 in apart, 2x4 on edge |
| Roost per bird | 6 in (Penn State), 5-10 in (OSU), 6-8 in (OSU Ohioline) | Plan allowance 10 in; bars built are listed per plan |
| Pop door | no figure found in these sources | 12 x 14 in opening on the 4x6, 6x8 and 8x12 walk-in; 16 x 18 on the insulated 8x12 |
| Walk-in door | no figure found in these sources | 34 x 74 in on the 8x12 walk-in |
Our size calculator turns your count into these numbers, and the nest box and roost calculator does the bank and bar lengths. For mid-size flocks the picks are in 6 chickens, 10 and 20.