Coop Size Calculator
Last reviewed on 30 April 2026.
Use this tool to determine how much space your chickens need. Enter the number of chickens and select their approximate size to see the recommended coop and run dimensions.
How the figures are calculated
The numbers come from rules-of-thumb that have held up well across temperate-climate backyard flocks: roughly 4 square feet of coop floor per medium-sized hen and 8–10 square feet of run per hen as a comfortable minimum, scaled down for bantams and up for large breeds. The coop figure assumes the run is genuinely usable; if your birds are confined to the coop for part of the year — for example during snow or in heavy rain — increase the coop allowance and add solid sheltered run space rather than open mesh.
Why minimum space rules matter
Crowding is the single most common driver of behavioural problems in backyard flocks. Feather-pecking, bullying, broken eggs and stress-driven illness all rise sharply once stocking density crosses the comfortable threshold. The feather pecking guide and aggression guide trace many cases back to too little space. Going slightly above the minimum costs little and prevents the most expensive problems.
Adjustments worth making
- Climate. In hot climates, give more shaded run space; the coop can stay near the minimum if ventilation is generous. In cold climates, the coop matters more because birds spend more time inside.
- Mixed flocks. If you have a mix of large breeds and bantams, size to the larger figure. Roosters need a little more space than hens of the same breed.
- Free-ranging. A few hours of daily free-ranging effectively expands the run and lets you stay closer to the minimum on the enclosed side.
- Future flock growth. Most keepers add birds within two years. Building in 25% extra capacity now is cheaper than rebuilding later.
For the wider context — choosing a layout, materials and predator-proofing your build — see the coop size and design guide and the first-coop setup guide.