The Golden Rule: 4 Square Feet Per Hen
Ask any poultry extension service how much indoor space a laying hen needs and you will hear the same number: 3 to 4 square feet per standard bird, with 4 being the comfortable, widely recommended figure. CoopCount uses 4. That number is not arbitrary — it is the floor area at which hens can move, stretch, flap, and establish a pecking order without the chronic stress that comes from crowding. Crowded coops do not just look sad; they produce feather-pecking, bullying, respiratory illness from ammonia buildup, and fewer eggs.
The run gets its own rule: 8 to 10 square feet per bird of outdoor run space (CoopCount uses 10). The run is where chickens spend their days scratching, dust-bathing, and foraging — the behaviors that make a chicken a chicken. Skimp on the run and you get bored birds, and bored birds are destructive birds. Note that both numbers describe floor area. Height does not count — you cannot stack chickens.
Bantams, Heavy Breeds, and Mixed Flocks
Not all chickens are the same size, so one number does not fit all. Bantams — the miniature breeds — need roughly half the room: about 2.5 square feet indoors and 6 square feet of run each. Heavy breeds like Jersey Giants and Brahmas, tipping past 10 pounds, want 5+ square feet indoors and 12 in the run.
Mixed flocks need mixed math, which is why CoopCount counts standards and bantams separately instead of pretending every bird is average. One caution for mixed flocks: size differences create pecking-order problems. Bantams get shouldered off feeders and roosts by bigger hens. The fixes are cheap — a second feeder, a lower roost just for the little ones, and sightline breaks (a straw bale, a branch) so a chased bird can duck out of view.
Nest Boxes: One Per Four Hens
The published guidance is one nest box per 4 to 5 hens, and CoopCount plans one per four. Hens are hilariously synchronized layers — give twelve hens three boxes and they will queue for the same favorite one while the others sit empty. That is normal; do not build twelve boxes.
Each box should be about 12×12 inches (a bit bigger for heavy breeds), filled with pine shavings or straw, positioned lower than the roosts (so birds sleep on roosts, not in nests — sleeping in nests means filthy eggs), and placed in the dimmest part of the coop. Hens like privacy. A curtained nest box is not fussy; it is good design.
Roosts: 10 Inches of Bar Per Bird
Chickens sleep on roosts, not on the floor — it is an anti-predator instinct. Plan 8 to 10 inches of roost bar per bird so everyone gets a spot without midnight shoving matches. Use 2×4 lumber with the wide side up (in cold climates this lets feet stay flat and fully covered by belly feathers, preventing frostbite), mount roosts 2 to 4 feet off the ground, higher than the nest boxes, and leave 12–18 inches of horizontal clearance from the wall so tails do not brush it.
Multiple roosts should be at the same height, not stair-stepped — otherwise every bird fights for the top bar. Under the roosts goes the droppings board or deep litter: most of a flock's manure lands in one predictable strip, which makes cleaning a five-minute job instead of a coop-wide excavation.
Coop-Only, Coop + Run, or Free Range?
Coop + run is the standard backyard setup and the happiest compromise: secure nights, sunny days. Coop-only (sometimes called a tractor or confined coop) suits small yards and strict predator pressure, but the birds live indoors full time — give them extra floor space if you can, plus enrichment: perches at different heights, a dust bath box, hanging greens. Boredom in a coop-only flock turns into feather-pecking fast.
Free range is the dream and the risk. Ranging birds still need the full coop space — nights, storms, and predator lockdowns happen, and a flock accustomed to acres will riot in a closet. The honest cost of free range is predation: hawks by day, raccoons and foxes by night. Most successful free-rangers use supervised ranging or a large fenced paddock rather than true open range, and lock the pop door at dusk without exception. An automatic pop door on a timer is the single best purchase a chicken keeper makes.
Ventilation Without Drafts
The most misunderstood sentence in chicken keeping: chickens need lots of ventilation and zero drafts. Both at once. Ventilation means ammonia and moisture escape near the roof — high vents, ideally on two sides for crossflow. Drafts mean cold air blowing across roosting birds at night. The fix is geometry: vents up high, roosts below and out of the airflow path, and no gaps at roost level.
Moisture is the real winter enemy, not cold. A dry, ventilated coop at 10°F houses healthier birds than a damp, sealed one at 30°F. Damp air plus droppings equals ammonia, and ammonia burns lungs and invites respiratory disease. If your coop smells like ammonia when you open the door, you do not have a space problem — you have a ventilation and bedding problem. Deep litter (8–12 inches of shavings, stirred regularly) composts gently, generates a little heat, and only needs a full clean-out a few times a year.
Winter Math: When the Run Disappears
In snowy climates, the run effectively vanishes for weeks — birds refuse to walk in snow, and you cannot blame them. Winter is when the 4-square-foot rule earns its keep: a flock that was “fine” at 3 square feet in summer starts fighting in January. If you live where winters lock birds inside, build to the full 4 (or a touch more) and consider it non-negotiable.
Cold-hardy breeds handle subzero nights in an unheated, ventilated coop without heat lamps — and heat lamps are a genuine fire hazard responsible for countless coop fires each winter. What cold birds need is more feed (digestion is their furnace — offer extra scratch grains before roosting time), unfrozen water (a heated base beats hauling buckets), and wide roosts for warm feet. Combs and wattles of large-combed breeds can frostbite; a thin coat of petroleum jelly on the worst nights helps.
Feed: A Quarter Pound a Day
A laying hen eats roughly ¼ pound of feed per day — about 1.5 pounds a week, 6–7 pounds a month. CoopCount's monthly estimate multiplies that by your flock: six hens run through about 45 pounds a month, essentially one 50-pound bag. Layers in peak production, growing pullets, and cold-weather flocks eat a bit more; bantams and light breeds a bit less.
Feed is the recurring cost that surprises new keepers, so budget it honestly: a 50-pound bag of layer feed is the unit of chicken economics. Store it in a metal can with a tight lid — mice, rats, and raccoons all consider an open feed bag an invitation, and damp feed grows mold that can kill birds. Fermented feed (soaked 2–3 days) stretches the bag a little and birds love it, but it is optional, not required.
Predator-Proofing: Build Like a Raccoon Is Watching
Because one is. The predator list — raccoons, foxes, coyotes, hawks, owls, opossums, skunks, rats, neighborhood dogs — reads like a nature documentary, and every one of them has defeated a “good enough” coop. The non-negotiables: ½-inch hardware cloth on every opening (chicken wire keeps chickens in; it does not keep anything out — raccoons shred it), buried 12 inches or skirted outward 18 inches to stop diggers, a solid floor or buried wire under the coop, and latches raccoons cannot operate (they open simple hooks and slide bolts — use carabiners or locking hasps).
Size the run's wire for the smallest threat: rats and weasels pass through 1-inch mesh. Cover the run top — hawks and climbing raccoons treat open runs as serving suggestions. And lock the pop door every single night. Every keeper who skipped “just once” has a story; you do not want yours.
The “Chicken Math” Expansion Rule
Every chicken keeper knows the phenomenon: you plan for six hens, and somehow you have eleven. “Chicken math” is half joke, half law of nature — there is always a irresistible breed, a friend rehoming pullets, a hatch that went well. Build 20% bigger than today's flock and thank yourself later. An 8-hen coop for 6 hens costs little extra in lumber and saves you rebuilding (or overcrowding) within two years.
The same logic applies to the run: fence the bigger area now, while the posts and wire are already out. Future you, carrying home three surprise Silkies, will be grateful.
Common Sizing Mistakes
Counting the nest boxes as floor space. The 4 square feet is open floor the birds actually stand on — boxes, feeders, and waterers do not count toward it.
Forgetting the human. You need to get in there to clean, collect eggs, and catch birds. A coop you cannot stand or reach into becomes a coop you do not maintain. Minimum human door: big enough for you plus a rake.
Building exactly to the minimum. Minimums assume perfect management. Real life includes a broody hen hogging space, an injured bird in recovery, and winter. Build past the minimum.
Ignoring the run's ground. A run on bare dirt becomes a mud pit and then a dust bowl. Plan for deep wood chips (free from tree services), which drain, compost the droppings, and give birds something to scratch.