Hen & Herd
Chicken Calculator

How much space do your hens actually need?

Based on Cooperative Extension System guidance, with or without outdoor run access.

🇬🇧 UK version/🇺🇸 US version
Standards usedExtension System guidanceOutdoor run access
Outdoor run access?
Coop floor space needed
/

16.0 sq ft

4.00 sq ft per hen × 4 hens (with run access)

Feed cost calculator · Water calculator · Bedding calculator · Cost of keeping calculator

Outdoor run space

40.0 sq ft

10.0 sq ft per hen recommended

What this means

A roughly square coop floor would be about 4.0ft × 4.0ft. A rectangular coop works better than a perfect square for most small flocks.

Example dimensions: 4.0ft × 4.0ft, 3.0ft × 5.3ft, 2.2ft × 7.3ft. Leave room for a nest box, feeder and waterer outside the core floor figure above.

Working backwards: how many chickens fit?

There is no US federal or state law setting a minimum chicken coop size. Figures here follow Cooperative Extension System guidance — the eXtension.org multi-university consortium for indoor space and run recommendations, and Oregon State University Extension for the no-outdoor-access figure. This tool is a planning guide, not professional advice — check with your local extension office or veterinarian before building.
How we calculated this +

Coop floor space needed (with run access)

Applies to:
United States — no federal or state law sets a minimum; this is the closest thing to a national reference for backyard flocks
Assumption:
Published as a 3–4 sq ft per hen range for hens with outdoor run access; the top of the range is used for a more conservative figure.
Calculation:
4 sq ft per hen, multiplied by hen count.

Coop floor space needed (no outdoor access)

Applies to:
United States — hens confined to the coop full-time
Assumption:
Published as an 8–10 sq ft per hen range; the midpoint is used since hens confined full-time spend all their time in that one space.
Calculation:
9 sq ft per hen, multiplied by hen count.

Outdoor run space

Applies to:
United States
Assumption:
A single recommended figure, not a range.
Calculation:
10 sq ft per hen, multiplied by hen count, on top of coop floor space (not instead of it).

Why there's no legal minimum shown

Source:
N/A — absence of law
Applies to:
United States
Assumption:
There is no US federal or state law setting a minimum chicken coop size, unlike the UK. The figures above follow Cooperative Extension System guidance, an industry/academic reference rather than a legal requirement.
Calculation:
No calculation — this entry documents an absence, not a figure.

Sources checked: September 2026.

Rules can depend on where you live. National welfare requirements aren't the same thing as local planning, registration, nuisance or disease-control rules — check with your local authority before you build or buy.

What this means

There's no US federal or state law setting a minimum chicken coop size, unlike the UK. In its absence, the figures here follow the Cooperative Extension System — the nationwide network of university extension services that's the closest thing the US has to a standard reference for backyard flocks.

With outdoor run access, eXtension.org's multi-university guidance recommends 3–4 sq ft of coop floor per hen; we use the higher end for a more conservative figure, plus 10 sq ft of run space per hen. Without outdoor access, hens need substantially more indoor room — Oregon State University Extension recommends 8–10 sq ft per hen; we use the midpoint, since hens confined full-time spend all their time in that one space.

Technical methodology +

The source, assumption and arithmetic behind each figure are in “How we calculated this” above.

Sources checked: September 2026.

Common questions

Is there a legal minimum coop size in the US?
No. There is no US federal or state law setting a minimum chicken coop size. The figures here follow an industry guidance body (Cooperative Extension System), not a legal requirement.
Why does no outdoor access mean a bigger coop?
Hens confined to the coop full-time spend all their time in that one space, so extension guidance recommends significantly more indoor floor area than hens who also have daytime run access.
Does this apply if I only keep a couple of hens?
The per-hen figures still apply, but for a very small flock most keepers choose a larger coop than the strict minimum suggests — pre-made coops are generally sized for practical use, not the bare minimum figure.
Do bantam or smaller breeds need less space than the figures above?
Generally yes, proportionally, but the published guidance is written for standard-size hens. If you're keeping a smaller breed, treat these figures as a safe upper bound rather than assuming a precise reduction.
Does a run need more than just chicken wire to be predator-proof?
Yes — predators dig under fences and reach through standard chicken wire, so a genuinely secure run typically needs buried or apron wire at the base and hardware cloth with a smaller mesh size. It's an easy thing to underbudget for when planning a coop-and-run setup — see our guide to what chickens actually cost.
Are backyard chickens allowed where I live?
In most US residential areas, yes — chickens are the most commonly permitted backyard animal because they're quiet, small and low-impact. Roosters are the usual exception: many places that happily permit hens ban roosters specifically over crowing noise. Check your local zoning rules for any flock-size cap or registration requirement — our guide to backyard chicken-keeping rules has more detail.
Is there a version of this for the UK?
Yes — see our UK chicken coop size calculator, based on the statutory welfare code and the RSPCA Assured standard.

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Want to see what keeping chickens is actually like?

Try My Backyard — a simple interactive simulation. Adopt one, feed it, play with it, keep its bedding clean, and see how it gets on.

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