Chicken coop size calculator
Tell us your flock. Get the coop and run square footage, monthly feed cost, nesting boxes, and winter ventilation — per the published extension-service standards, rounded up.
The rule everyone argues about on r/BackYardChickens, applied for you: 4 sq ft of coop + 10 sq ft of run per standard bird (2 + 8 for bantams).
Prefab coops matched to common flock sizes on Amazon — 4×6 walk-ins for 6-8 hens, 8×12 for 15+.
A standard laying hen eats about ¼ lb of layer feed per day. Here's what your flock goes through — and what it costs per egg.
Storing bulk feed? A 30-gallon metal trash can holds about 150 lb — a full pallet-order math check is in the feed cost guide.
Layer feed, gravity feeders, and rodent-proof storage cans on Amazon:
One box per 3-4 hens is the standard. More than that and they'll all lay in the same one anyway.
Nesting box kits, roll-out nest inserts, and fake ceramic training eggs on Amazon:
Adults rarely need heat — damp air is the winter killer, not cold. Size your high vents and brooder bulb here.
Coop thermostats, red brooder bulbs, and vent covers on Amazon:
How coop sizing works
Two numbers decide the build. Coop interior — 4 sq ft per standard bird if they also have a run (2 sq ft for bantams); if the coop doubles as the run, double it. Run — 10 sq ft per standard bird (8 for bantams). These come from the guidance published by state extension services and repeated in every serious backyard-flock book. The floor plans work out to a 4×6 ft coop for 6 hens, an 8×8 for 12, and roughly a 10×12 for 25+.
The other constraint is roost bar length: plan 8-10 inches of roost per bird, so 12 hens need 8-10 ft of roosting bar regardless of floor math. Nesting boxes are separate — one per 3-4 hens, and hens will queue to lay in the same box no matter how many you build.
Quick reference by flock size
| Flock | Coop sq ft | Run sq ft | Nest boxes | Feed / month |
|---|---|---|---|---|
| 3 hens | 12 | 30 | 1 | 23 lb (~1 bag / 2 mo) |
| 6 hens | 24 | 60 | 2 | 46 lb (~1 bag / mo) |
| 12 hens | 48 | 120 | 3–4 | 91 lb (~2 bags) |
| 25 hens | 100 | 250 | 7–9 | 190 lb (~4 bags) |
Standard-size birds, ¼ lb feed/day each, $22 per 50 lb bag as the default price.
Guides
Best chicken coops for 6 hens (2026)
What a real 24+ sq ft coop costs, prefab vs DIY vs kit, and the specs that matter — roost length, vents, predator latches.
What does it cost to feed backyard chickens?
Feed math per flock size, cost per egg, layer vs flock-raiser, and the storage setup that stops rodents eating your margin.
Do chickens need a heat lamp in winter?
Why vents beat heaters, the frostbite myth, brooder wattage by week, and how not to burn the coop down.
GeneratorSizer ↗ SolarSizer ↗ WeldingCalc ↗ Battery Bank Sizer ↗
Running the coop off-grid? Size the generator, solar array, welder circuit, or battery bank with the sister tools.