Chicken Coop Size Calculator
Enter your flock and get the space numbers that experienced keepers and university extension services actually recommend — not the capacity printed on a coop box. Then take the numbers to our coop buying guides.
Your recommended setup
| Coop interior floor | |
|---|---|
| Run space | |
| Roost bar length | |
| Nest boxes | |
| Feeder space (linear) | |
| Water capacity to plan for | |
| Bedding volume for that floor |
The math behind the numbers
- Coop floor: ~4 sq ft per standard bird with run access (3 bantams, 5 large breeds). Coop only, no run? Double it: 8 sq ft per standard bird — the conservative end of the 8–10 planning band, and the same figure the capacity checker uses.
- Run: ~10 sq ft per bird in an attached run; free-range flocks can drop to 8. The coop floor never drops below the with-run figure — nights are when space matters.
- Roost: 8–12 inches of bar per bird.
- Nest boxes: one box per 4 hens.
- Feeder space: ~2.5 inches of linear feeder space per bird, so every bird can eat at once.
- Water: plan roughly 1 gallon of capacity per 4–5 birds per day; actual intake is lower (roughly half a pint to a pint per bird in moderate weather) — the rest is headroom. More in heat, less in cold.
- Bedding: the volume row converts your coop floor to loose shavings at 2 and 4 inches deep, so you can bracket it. Divide by the cubic-feet number printed on your bag for a bag count — shavings are sold compressed, so fluffed coverage is bigger than the bag looks.
These are widely used rules of thumb for planning, not veterinary advice — bantams, climate and breed temperament all shift the numbers. Sources: eXtension — space allowances (3–4 sq ft indoor, 10 sq ft outdoor), Penn State Extension — small flock guide (the top of that published indoor range is what this tool uses), and large keeper communities (BackYardChickens.com, r/BackYardChickens).