Backyard chicken calculators
How big a coop, how much vent area, how much feed, what brooder temp. Calculator-driven research for backyard flocks.
Coop floor
18–30
sq ft
6 standard hens, run access
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Vent area
2.9–3.5
sq ft
32 sq ft coop, temperate
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Feed
1.3–2.0
lb / day
6 layer hens
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Brooder · wk 1
90–95
°F
Drop 5°F per week
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Live numbers from each calculator's default inputs. Click any card to tune the inputs to your flock.
Calculators
See all →Coop ventilation
Total vent area for a backyard coop, split between high outlets and low intakes, by climate and breed weight.
Sq ft of vent area, climate-adjusted
Brooder heat lamp
Target temperature at chick level + advisory wattage. Temperature-led, not wattage-led.
90–95°F week 1, drop 5°F per week
Coop size + run space
Indoor floor area + outdoor run footprint by flock count, breed, climate, run hours.
3–5 sq ft indoor (with run access)
Feed amount
lb/day, lb/week, lb/month + bag-size and reorder cadence. Adjusts by life stage and free-range supplement.
100–150 g/day per laying hen
Ask a HatchMath question
Free, no signup. Quick answers on coop math, ventilation, feed, and brooder questions. Not veterinary advice.
Hi, I'm the HatchMath assistant. I answer questions about backyard chicken keeping math — coop sizing, ventilation, feed, brooder and incubation setpoints — and how the calculators on this site work. I'm not a veterinarian and can't diagnose or treat sick birds. For health emergencies, talk to an avian or poultry vet or your county extension agent.
Recent guides
Coop ventilation, explained
Why sealed coops fail in winter, the stack-effect physics behind high+low vents, and where the 1:10 rule of thumb comes from.
How to incubate chicken eggs
21-day walkthrough — temperature, humidity, turning, candling, lockdown — anchored on UMD Extension FS-1114.
How many chickens fit in a 4×8 coop?
6–8 standard hens with daily run access. Heavy breeds and full confinement change the answer. Calculator prefilled.
Frequently asked
What does HatchMath actually do?
HatchMath publishes calculators and short reference pages for backyard chicken keepers. Where the published guidance gives a range, the calculator shows the range. Where HatchMath synthesizes practitioner consensus into a number that isn't directly published, the page labels it HatchMath methodology and surfaces the assumption.
Who is HatchMath for?
Backyard keepers and small-flock owners who want sourced math. Specifically: anyone deciding how big to build a coop, how much ventilation it needs, what wattage of brooder lamp to buy, how much feed to order monthly. The site doesn't publish breed shopping lists or sick-bird diagnostics — those go to a poultry vet or your county extension office. HatchMath is calculator-first; the prose supports the calculator.
Why ranges instead of single numbers?
Because the verified extension working set publishes ranges — and chicken keeping varies enough by climate, breed, bedding management, and coop layout that single-answer precision would be misleading. OSU Extension EC-1644 publishes 3 sq ft per bird with run access vs 8–10 sq ft for full confinement. UMN Extension publishes 3–5 sq ft indoor. Penn State and University of Maryland publish ~2 sq ft for layer floor pens. Ranges are honest about what's actually published; single numbers would imply a precision the sources don't support.
Do I need a heat lamp for adult chickens in winter?
Almost never. Heat lamps are a real fire risk, and supplemental heat in a sealed coop creates the condensation that produces frostbite — exactly the problem most beginners think the heat lamp prevents. Adult layers handle below-freezing dry coops without distress. The conservative answer for adult flocks in winter is: no heat lamp, more vent area, dry deep-litter bedding, roost shape that lets birds tuck their feet under their feathers. See the coop ventilation guide for the underlying physics.