Chicken Coop Size Calculator: Space, Eggs and Feed Cost

Ventilation

No extension service publishes a vent area for a backyard coop — not one of the fourteen I read, including the single page in the whole extension system written specifically about it. What they publish instead is a test: damp litter or a smell of ammonia means there is not enough air moving for the number of birds you have. The full account, including the one number that is published, is on chicken coop ventilation.

Feed intake

Bird and stage	Feed per day	Source
Mature laying hen	0.25 lb (100 to 150 g)	Alabama Cooperative Extension ANR-2913; Oklahoma State Extension
Mature laying hen, planning figure including waste	about 0.29 lb	Derived from the University of Maryland 100-hen budget (80 bags of 50 lb over 550 days for 25 hens equivalent)
Chicks	0.1 lb	Oklahoma State Extension
Hatch to point of lay, total	13 to 15 lb per bird	Oklahoma State Extension
Day 1 to 6 weeks, starter	at least 4 lb per bird total	University of Georgia Extension C969
Cold weather	up to 25% more	University of Minnesota Extension
Hy-Line Brown standard, week 18 to 33	87 to 91 g per day	Hy-Line Brown performance standards
Hy-Line Brown standard, week 34 to 48	98 to 103 g per day	Hy-Line Brown performance standards
Hy-Line Brown standard, week 49 onward	105 to 110 g per day	Hy-Line Brown performance standards
Bantam	not published	No extension or breeder source publishes a bantam intake figure. The tool uses the standard-hen number and says so.

Egg production, and what the flock really lays

Figure	Eggs per hen per year	Source and context
US commercial average, 2025	288	USDA NASS, Chickens and Eggs 2025 Summary: "The annual average production per layer on hand in 2025 was 288 eggs, down 1 percent from 2024." Note this is production per layer on hand across a 365-million-bird inventory, including birds mid-molt or at the end of lay, for the year ending 30 November 2025. It is not the same measurement as a breed's peak-year potential.
Commercial sex-linked hybrid	240 to 280	Penn State Extension, Successfully Raising a Small Flock of Laying Chickens
Commercial egg-type birds	200 to 260	Penn State Extension, Management Requirements for Laying Flocks — a different Penn State page
Single Comb White Leghorn	about 265	Oregon State Extension
Enterprise budget assumption	about 256	University of Maryland: flat 70% lay over a 550-day, two-year flock
Conservative budget assumption	about 182	Oklahoma State Extension: "a chicken would lay an egg every other day"
Heritage type breed	50 to 100	Penn State Extension, Successfully Raising a Small Flock of Laying Chickens: "There is also great variability between strains."
Purebred poultry	100 to 180	Penn State Extension, Management Requirements for Laying Flocks — the same institution, a different page, a range that does not overlap the one above

The shape of the year matters as much as the total. UF/IFAS publishes the curve: production starts at 18 to 22 weeks, peaks around 90% about 6 to 8 weeks later, then declines to about 65% after 12 months of lay. Good layers run 50 to 60 weeks and then molt. Penn State assumes flocks stay above 60% production to 80 weeks of age.

Gap flagged No extension service publishes a percentage decline for the second or third laying year. We looked at Kentucky ("hens will lay fewer eggs each year", no number), Oregon State ("chickens produce well until they are 2 to 3 years old, and then egg production declines") and Minnesota (peak in the first two years). The 12.5%-per-year figure this tool applies to years two and three is derived from Hy-Line Brown measured hen-day rates — 92.8 to 96.6% at week 30, 85.3 to 89.2% at week 70, 76.5 to 80.2% at week 90 — and is labeled as derived everywhere it appears. It is not a quoted extension figure and we are not going to present it as one.

Water, light, mortality

Item	Published figure	Source
Water, cool weather	0.05 gal per hen per day	Penn State: at least 5 gallons per 100 birds daily
Water, planning figure	0.075 gal per hen per day	Oklahoma State Extension
Water, hot weather	about 0.106 gal per hen per day	University of Kentucky Table 12.1, layers at 89.6 degrees F
Water to feed ratio	about 2:1 by weight	University of Kentucky; Alabama Extension. Under extreme heat stress, requirements "may easily quadruple".
Light to sustain lay	14 hours per day	University of Kentucky ASC-192; UF/IFAS; Poultry Extension Collaborative
Light below which lay stops	under 12 hours	University of Kentucky: "production will decrease and often stops"
Light ceiling	16 hours, not more	Penn State. Birds need at least 15 minutes of darkness (Oklahoma State).
Mortality, small flocks	about 10% per year, 20% over two years	University of Maryland layer budget and small-flock economics page
Labor	about 15 minutes per day	Oklahoma State Extension budgeting fact sheet

What a dozen eggs actually costs

Published budget	Layer feed price	Cost per dozen	Source
Small Layer Flock Budget, 2010 data	$11.00 per 50 lb	$1.37	University of Maryland Extension, Economics of Small Poultry Flocks
Small Flock Layer Budget, 100 hens, updated 2022	$14.00 per 50 lb	$2.07	University of Maryland Extension (Dale M. Johnson), 3,208 dozen over two years, total feed $4,972

Gap flagged USDA publishes no retail layer-feed price series. We checked the AMS Oklahoma Retail Feed Cost Report, which carries cattle cubes, creep pellets, corn, cottonseed meal, alfalfa and bulk commodities — and no poultry line items at all. That is why the feed price in this tool is a field you fill in rather than a number we assert.

The method, in plain text

A worked example you can check by hand

Six standard laying hens with a run, planned on the Maryland enterprise-budget basis of 256 eggs, first laying year, 0.25 lb of feed a day, three cold months, feed at $14.00 per 50 lb bag:

• Coop floor: 6 x 1.5 = 9 sq ft at the Penn State and Maryland end; 6 x 4 = 24 sq ft at the Poultry Extension Collaborative end. A 4x6 coop meets the high figure.
• Run: 6 x 10 = 60 sq ft. That is the number both camps agree on.
• Roost: 6 x 6 in = 36 in = 3 linear feet at the low published figure; 6 x 10 in = 5 feet at the high.
• Nest boxes: 2 by the Maryland ratio of one per four to five hens; 3 by Penn State's rule of two nests for the first four hens plus one for every four additional. Penn State's laying-flock page separately calls for a minimum of four boxes regardless of flock size.
• Feed: 6 x 0.25 x 365 = 547.5 lb before the winter adjustment. Three cold months at 25% more adds 6 x 0.25 x 91.2 x 0.25 = 34.2 lb, so 582 lb a year, which is 12 bags and $163 at $14 a bag.
• Eggs: 6 x 256 = 1,536 eggs, which is 128 dozen, about 30 eggs a week.
• Feed cost per dozen: $163 / 128 = $1.27. Feed is not the whole cost — Maryland's full budget, which includes bedding, birds and other inputs, lands at $2.07 a dozen.
• Water: 6 x 0.05 = 0.3 gal a day in cool weather, rising to about 0.64 gal a day at 90 degrees F.
• Birds to order: 6 x 1.10 = 7, to absorb the roughly 10% annual mortality Maryland reports for small flocks.

How to read your result

• Build to the high end of the coop range if you can afford the lumber. The literature gives you a defensible floor at 1.5 square feet, but nothing in it says crowding is better. The Poultry Extension Collaborative's point about confinement is the operative one: if winter keeps the birds inside, the indoor requirement goes up.
• The run number is the one to take seriously. 10 square feet per bird is the only figure both camps publish.
• Where two sources disagree, plan on the lower number. Penn State publishes two non-overlapping purebred egg ranges on two live pages. Nobody is going to be upset by a surplus of eggs.
• Feed cost per dozen only counts feed. Maryland's published $2.07 includes birds, bedding and other inputs. If your feed-only number looks cheap, that is because it is incomplete, not because you have beaten the budget.
• Plan the flock for year two, not year one. Production falls, mortality accumulates, and the coop you build this spring is the coop you have in three years.
• Check your local ordinance before you buy lumber. Rooster rules, setbacks, flock caps and permit requirements are municipal and vary enormously. No national source covers them.

Final Thoughts

Build to the strict end of every range on this page. Remember that you cannot add square footage to a finished coop without a saw! Floor space, roosts, nests, feeder space — the published figures disagree by a factor of two and a half, and I have never once regretted the extra square foot. Crowding is what turns a healthy flock into a feather-picking, damp, ammonia-smelling problem, and you cannot add floor area in February.

Two pieces of this deserve their own page and now have one: how many nesting boxes per chicken, where eleven institutions give answers from two boxes to four for the same dozen hens, and chicken coop ventilation, where none of them give you a number at all.

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Frequently asked questions

How much space does a chicken need?

There are two published answers, not one. Penn State, the University of Maryland, Virginia Tech's Table 1 and Oklahoma State publish 1.5 to 2 square feet of indoor floor space per laying hen. The Poultry Extension Collaborative, the University of Georgia and Texas A&M publish 3 to 4. Both camps publish 10 square feet per bird for the outdoor run, which is the figure to build to with confidence.

What size coop do I need for 6 chickens?

Between 9 and 24 square feet of indoor floor, depending on which published standard you follow, plus 60 square feet of run. A 4x6 coop satisfies the most generous extension figure. You also want 3 to 5 linear feet of roost and at least 2 nest boxes, though Penn State separately recommends a minimum of four regardless of flock size.

How many chickens fit in a 10x10 coop?

100 square feet holds 25 hens at the conservative published rate of 4 square feet each, 50 hens at 2 square feet, or 66 at the 1.5-square-foot minimum. Bear in mind that the run, not the coop, is usually the binding constraint: 25 hens need 250 square feet of run at the agreed 10-square-feet-per-bird figure.

How much feed does a chicken eat per day?

A quarter of a pound, or 100 to 150 grams, for a mature laying hen — Alabama Extension and Oklahoma State both publish that figure. Ten hens go through a 50-pound bag in roughly 20 days. Minnesota Extension reports intake can rise up to 25 percent in cold weather. Hy-Line's published standards run 87 to 91 grams a day early in lay and 105 to 110 grams later, which brackets the extension figure.

How many eggs will my chickens actually lay?

Somewhere between 50 and 288 a year, and which end you land on depends almost entirely on breed. Penn State puts heritage type breeds at 50 to 100 eggs a year and commercial sex-linked hybrids at 240 to 280 on one page, and purebred poultry at 100 to 180 with commercial egg-type birds at 200 to 260 on another. Both pages are live, and the two purebred ranges do not overlap. USDA NASS reports the 2025 commercial average at 288 eggs per layer on hand, which is an inventory-wide figure including birds mid-molt, not a breed potential. UF/IFAS publishes the shape of the year: lay peaks around 90 percent about 6 to 8 weeks after it starts, then falls to about 65 percent after 12 months. Any single "300 eggs a year" number you see is the very top of a very wide range.

Sources

1. Poultry Extension Collaborative, Space Allowances in Housing for Small and Backyard Poultry Flocks
2. Poultry Extension Collaborative, Ventilation in Small and Backyard Poultry Flock Housing
3. Poultry Extension Collaborative, Raising Chickens for Egg Production
4. Penn State Extension, Small Scale Poultry Housing
5. Penn State Extension, Successfully Raising a Small Flock of Laying Chickens
6. Penn State Extension, Management Requirements for Laying Flocks
7. University of Maryland Extension, Housing Requirements
8. University of Maryland Extension, Economics of Small Poultry Flocks
9. University of Maryland Extension, Small Flock Layer Budget - 100 (Dale M. Johnson)
10. Virginia Cooperative Extension, Small-scale Poultry Housing (2902-1092)
11. Oklahoma State University Extension, Backyard Flock Production
12. Oklahoma State University Extension, Simple Budgeting and Pricing Calculations for Backyard Hens
13. University of Georgia Extension, Management Guide for the Backyard Flock (C969)
14. Texas A&M AgriLife Extension, The Small Laying Flock
15. Alabama Cooperative Extension System, Feeding the Laying Hen (ANR-2913)
16. University of Minnesota Extension, Caring for chickens in cold weather
17. University of Minnesota Extension, Raising chickens for eggs
18. University of Florida IFAS Extension, Factors Affecting Egg Production in Backyard Chicken Flocks (PS-35/PS029)
19. Oregon State University Extension, Why Did My Chickens Stop Laying? (PNW 565)
20. University of Kentucky, Poultry Production Manual, Chapter 12
21. USDA National Agricultural Statistics Service, Chickens and Eggs 2025 Summary (February 2026)
22. USDA APHIS, Defend the Flock
23. USDA Agricultural Marketing Service, Oklahoma Retail Feed Cost Report
24. Hy-Line International, Hy-Line Brown Alternative Systems Performance Standards

[IMAGE NEEDED: at least 1200px wide featured image. Suggested subject: a backyard coop and attached run photographed from outside at an angle that shows both structures, with hens visible in the run. Alt text: backyard chicken coop with attached run and laying hens.]