Chicken Coop Size Calculator
Coop, run, nest boxes, and roost from flock size and breed.
What it does
Crowded coops pay in pecking, disease, and thin shells, so space math comes before lumber. Standard layers at 3 square feet indoors plus 8 of run each turn six hens into 18 square feet of coop with a 48 square foot run. The tool above sizes floor, run, nests, and roost from any flock.
The default also fits out the interior: six hens split into 2 nest boxes at one per four, with 60 inches of roost bar at 10 inches each. Bantams halve the footprint while heavy breeds stretch it, and confined flocks with no run at all need roughly double indoor room.
University extensions converge on the allowances. Maryland tables layers at 1.5 to 2 square feet inside with 8 of run, Oregon State asks 3 square feet with run access, and Virginia Tech with Delaware settle standard hens near 3 to 4 inside with 8 to 10 of run. Nest guidance repeats everywhere at one box per three to four hens.
Minimums are floors, not targets. Cold climates that lock birds inside for weeks want the generous end, roosts must outrank nests or hens sleep where they lay, and feeders with waterers need their own inches beside the floor math.
How to use
- Type the number of hens.
- Pick bantam, layer, or heavy breed.
- Read coop floor first for the build.
- Read run area for the fenced yard.
- Fit nests and roost from the setup line.
Formula
- inside
- 2 bantam, 3 layer, 4 heavy ft2 per bird.
- run
- 5 bantam, 8 layer, 10 heavy ft2 per bird.
- nests
- One 10 to 12 in box per four hens.
Minimums with run access; double indoor space for fully confined flocks. Local ordinances may cap flock size regardless of math.
Worked example
Example: 6 standard layers
Defaults: 6 birds, layer.
- Coop: 6 x 3 = 18 ft2, such as 4 by 4.5 ft.
- Run: 6 x 8 = 48 ft2, such as 6 by 8 ft.
- Nests: 6 / 4 = 1.5, round up to 2 boxes.
- Roost: 6 x 10 = 60 in of bar.
- Tool shows 18 ft2, 48 ft2, 2 boxes + 60 in roost.
Reference table
| Hens | Coop | Run |
|---|---|---|
| 4 | 12 ft2 | 32 ft2 |
| 6 | 18 ft2 | 48 ft2 |
| 8 | 24 ft2 | 64 ft2 |
| 12 | 36 ft2 | 96 ft2 |
Limits
- Minimums with run access; confinement needs more.
- Breed sizes blur; measure your birds.
- Ordinances and HOAs override arithmetic.
- Feeders, waterers, and doors need extra inches.
Common mistakes
- Counting the run as indoor space.
- Buying dollhouse coops rated for twice the hens.
- Setting nests below roost height.
- Skipping ventilation for winter warmth.
- Forgetting winter confinement needs room.
Try it yourself
Quick checks. Answers sit tucked under each question.
4 bantams?
4 x 2 = 8 ft2 coop, 4 x 5 = 20 ft2 run, 1 box + 40 in roost.
10 heavy breeds?
10 x 4 = 40 ft2 coop, 10 x 10 = 100 ft2 run, 3 boxes + 100 in roost.
8 layers?
24 ft2 coop, 64 ft2 run, 2 boxes + 80 in roost.
Questions
Coop for 6 hens?
18 ft2 indoors with 48 ft2 of run for layers.
How many nest boxes?
One per four hens, so 2 for six.
Roost per bird?
About 10 inches of bar each.
Bantams different?
Yes: 2 ft2 inside with 5 of run each.
No run at all?
Roughly double the indoor allowance.
Where do nests go?
Below roosts, or hens sleep in them.
Sources
- U Maryland Extension: Poultry Housing Requirements
- Oregon State Extension: Backyard chicken coop design