Sources & Methodology

Coop floor space needed

Source:

Welfare of Farmed Animals (England) Regulations 2007 (non-cage systems); RSPCA Assured laying hen standards comparison (2025)

Applies to:

England — statutory minimum and RSPCA Assured members alike

Assumption:

A maximum stocking density of 9 hens per m² of usable floor area is identical under the legal minimum and RSPCA Assured — RSPCA's welfare uplift for hens comes from litter, enrichment and perch requirements, not extra floor space, unlike the pig calculator where the two standards differ.

Calculation:

1 ÷ 9 m² (about 0.11m²) per hen, multiplied by hen count.

Perch space needed

Source:

Welfare of Farmed Animals (England) Regulations 2007 (non-cage systems); RSPCA Assured laying hen standards comparison (2025)

Applies to:

England — statutory minimum and RSPCA Assured members alike

Assumption:

Specified identically by both the legal minimum and RSPCA Assured.

Calculation:

15cm per hen, multiplied by hen count.

Outdoor run space

Source:

British Hen Welfare Trust, hen-setup guidance

Applies to:

A daytime garden run — a different, smaller-scale figure than open free-range pasture

Assumption:

2m² per hen for most hens; the British Hen Welfare Trust sets a lower minimum (1m² per hen) specifically for ex-caged rescue hens while they adjust, which isn't broken out as a separate calculator result but is noted on the page.

Calculation:

2m² per hen, multiplied by hen count, on top of coop floor space (not instead of it).

Nest boxes

Source:

Widely-recommended keeper guidance, not a legal requirement

Applies to:

England and the US alike

Assumption:

1 nest box per 5 hens is a commonly recommended convention rather than a statutory or RSPCA Assured figure, shown as a supplementary tip rather than part of the core floor-space maths.

Calculation:

Hen count ÷ 5, rounded up.

Coop floor space needed (with run access)

Source:

eXtension.org, "Space Allowances in Housing for Small and Backyard Poultry Flocks" (Cooperative Extension System)

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)

Source:

Oregon State University Extension, "Living on the Land: Backyard Chicken Coop Design"

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

Source:

eXtension.org, "Space Allowances in Housing for Small and Backyard Poultry Flocks" (Cooperative Extension System)

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.

Indoor housing needed

Source:

RSPCA guidance for pet and backyard goats

Applies to:

UK — pet and backyard goats

Assumption:

The RSPCA gives a range of 2 to 2.5m² of indoor space per goat; we use the midpoint (2.25m²). Goats need access to this housing 24 hours a day, whatever the season, whether or not they also have paddock access — so the figure doesn't change with the outdoor-access toggle.

Calculation:

2.25m² per goat × goat count.

Outdoor paddock needed

Source:

RSPCA guidance for pet and backyard goats

Applies to:

UK — pet and backyard goats given outdoor grazing access

Assumption:

A flat per-head land figure, not a weight-banded table — reflecting how much land goats genuinely need to browse a varied diet of shrubs and rough forage, not just a simple exercise yard.

Calculation:

A quarter-acre (0.25 acre ≈ 1,011.7m²) per goat × goat count, shown only when outdoor access is selected.

Indoor shelter needed

Source:

University extension guidance (Oklahoma State University Extension; Penn State Extension and UMass Extension publish similar ranges)

Applies to:

United States — no federal or state law sets a minimum goat housing size

Assumption:

15 sq ft per goat is the practical starting point where goats also have outdoor exercise access; goats confined indoors for extended periods (e.g. winter) need closer to 25 sq ft per goat.

Calculation:

15 sq ft/goat (outdoor access) or 25 sq ft/goat (confined indoors) × goat count.

Outdoor exercise area needed

Source:

University extension guidance (Oklahoma State University Extension; Penn State Extension and UMass Extension publish similar ranges)

Applies to:

United States — goats given outdoor exercise access

Assumption:

A flat per-head exercise-area figure on top of the reduced (15 sq ft) indoor shelter figure that applies once outdoor access is given.

Calculation:

25 sq ft per goat × goat count, shown only when outdoor access is selected.

Housing space needed — ewe alone

Source:

DEFRA, Code of Recommendations for the Welfare of Livestock: Sheep (England)

Applies to:

England — lowland ewes, pregnant, no lambs at foot

Assumption:

Published as a range (1.2–1.4m² per ewe); we use the midpoint (1.3m²). Applies to indoor housing — typically lambing and winter housing, not year-round.

Calculation:

1.3m² × ewe count.

Housing space needed — ewe with lambs at foot

Source:

DEFRA, Code of Recommendations for the Welfare of Livestock: Sheep (England)

Applies to:

England — lowland ewes with lambs at foot, up to 6 weeks old

Assumption:

Published as a range (2.0–2.2m² per ewe + lambs); we use the midpoint (2.1m²) — about 50–60% more than the ewe-alone figure, to allow for bonding, nursing and lambs moving around safely.

Calculation:

2.1m² × ewe count.

Housing space needed — hill ewe alone

Source:

DEFRA, Code of Recommendations for the Welfare of Livestock: Sheep (England)

Applies to:

England — hill ewes (45–65kg live weight), pregnant, no lambs at foot

Assumption:

Same table (paragraph 116) as the lowland figures above, added 2026-09-22 once fetched directly from the source — the site previously only had the lowland rows. Published as a range (1.0–1.2m² per ewe); we use the midpoint (1.1m²).

Calculation:

1.1m² × ewe count.

Housing space needed — hill ewe with lambs at foot

Source:

DEFRA, Code of Recommendations for the Welfare of Livestock: Sheep (England)

Applies to:

England — hill ewes with lambs at foot, up to 6 weeks old

Assumption:

Published as a range (1.8–2.0m² per ewe + lambs); we use the midpoint (1.9m²).

Calculation:

1.9m² × ewe count.

Housing space needed — ewe alone

Source:

Ohio State University Extension, Small Ruminant Team; UMass Extension

Applies to:

United States — no federal or state law sets a minimum; extension guidance

Assumption:

Range given as 12–16 sq ft per ewe at maintenance through mid-gestation; we use the midpoint (14 sq ft).

Calculation:

14 sq ft × ewe count.

Housing space needed — ewe with lambs at foot

Source:

Ohio State University Extension, Small Ruminant Team; UMass Extension

Applies to:

United States

Assumption:

Range given as 15–20 sq ft per ewe once lambs are at foot; we use the midpoint (17.5 sq ft).

Calculation:

17.5 sq ft × ewe count.

Shelter + living area needed — small–medium

Source:

APGAW, "Good Practice Code for the Welfare of Rabbits" (2021)

Applies to:

England — small-to-medium rabbits; created to support Section 15 of the Animal Welfare Act 2006, backed by the RSPCA, Rabbit Welfare Association & Fund and British Veterinary Association

Assumption:

Published as a minimum for a compatible pair of small-to-medium rabbits — 3 x 2 x 1m (6m²) of shelter and living area combined, permanently accessible to each other — not a per-rabbit figure. Rabbits shouldn't be kept alone, so this is the floor for any group of 1-2.

Calculation:

6m² pair minimum, held as a floor for 1-2 rabbits. Beyond a pair, scaled at 3m² per rabbit (our own linear extension, not a published per-rabbit rate — the Code only says larger groups need more space) multiplied by rabbit count.

Why the floor is a pair minimum, not per-rabbit

Source:

APGAW, "Good Practice Code for the Welfare of Rabbits" (2021)

Applies to:

England

Assumption:

Rabbits are highly social, and a solitary rabbit is now widely considered a welfare problem in its own right — the Code states its minimum space figure for a compatible pair, not a single animal.

Calculation:

No calculation — this is why the 6m² figure is applied as a floor for any group of 1-2 rabbits, rather than halved for a single rabbit.

Shelter + living area needed — giant breed

Source:

Rabbit Welfare Association & Fund, "Caring for Giant Rabbits"

Applies to:

England — giant breeds (e.g. Flemish Giant, Continental Giant), added 2026-09-22

Assumption:

RWAF doesn't publish one area figure comparable to the standard 3x2x1m Code minimum for giants specifically. The only quantified figure it gives is daily exercise space of "over 20ft square", which we read as 20ft x 20ft (~37.2m²) — the natural reading of that phrasing, though the source itself doesn't spell out the arithmetic. It separately says giants should manage 3 consecutive hops in any direction (up to ~3.7m/12ft) and that pet-shop hutches are rarely adequate, both disclosed as qualitative context rather than folded into the number.

Calculation:

37.2m² floor for 1-2 giant rabbits. Beyond a pair, scaled at 18.6m² per rabbit (our own linear extension, same caveat as the standard-size figure — RWAF gives no giant-specific per-rabbit or multi-rabbit rate at all).

Enclosure & exercise space needed

Source:

House Rabbit Society guidance

Applies to:

United States — no federal or state law sets a minimum pet rabbit enclosure size

Assumption:

Published as a baseline for 1-2 rabbits (a bonded pair), not a strict per-rabbit rate — rabbits shouldn't be kept alone. We scale linearly per rabbit beyond that as a reasonable extension, not an officially published per-rabbit figure.

Calculation:

8 sq ft enclosure + 24 sq ft exercise space is the floor for 1-2 rabbits. Beyond 2, each is scaled at half its base figure per rabbit (4 sq ft enclosure, 12 sq ft exercise per rabbit), multiplied by rabbit count, each held at its 1-2-rabbit floor.

Why enclosure and exercise space are shown separately

Source:

House Rabbit Society guidance

Applies to:

United States

Assumption:

The exercise-space figure assumes 5+ hours of daily access, not occasional supervised playtime — a genuinely separate budget from the enclosure, not something a bigger enclosure can substitute for.

Calculation:

No calculation — the two figures are shown independently rather than combined into one number, since increasing one doesn't reduce the requirement for the other.

Giant breeds — a different kind of figure, not a bigger number

Source:

House Rabbit Society, "Living Space: How to set it up"

Applies to:

United States — giant breeds, added 2026-09-22

Assumption:

House Rabbit Society doesn't publish a giant-breed minimum area comparable to the 8/24 sq ft figures above. It gives a size-relative rule instead: "the cage should be three-four times the (stretched-out) adult body-length." That's a length rule, not an area, so it can't be converted into a single extra square-footage figure without also sourcing breed-specific body lengths, which we haven't done.

Calculation:

No calculation performed — shown as guidance for the visitor to apply directly (measure your own rabbit and multiply), rather than us computing a number on their behalf.

Indoor housing needed

Source:

RSPCA, "Indoor housing for pet geese & ducks"

Applies to:

England — RSPCA guidance for pet ducks

Assumption:

Published as a range (at least 1m² of floor space for every two to three ducks), not a single per-duck figure. We use the more generous end of that range — two ducks per m² (0.5m² per duck) — as the conservative reading, the same rounding convention used elsewhere on this site.

Calculation:

0.5m² per duck × duck count.

Why there's no outdoor land figure

Source:

RSPCA, "Indoor housing for pet geese & ducks"

Applies to:

England

Assumption:

RSPCA guidance doesn't give a matching outdoor land figure the way it does for indoor space — it's explicit that more outdoor and water access is simply better, without a single defensible minimum.

Calculation:

No calculation. We don't invent a headline outdoor number to fill the gap — it's discussed in the guide on how much space a duck needs.

Indoor housing needed

Source:

eXtension.org, "Space Allowances in Housing for Small and Backyard Poultry Flocks"

Applies to:

United States — multi-university Cooperative Extension consortium guidance; no federal or state law sets a minimum

Assumption:

A single recommended indoor figure, not a weight- or breed-banded table.

Calculation:

5 sq ft per duck × duck count.

Why there's no outdoor run figure

Source:

eXtension.org, "Space Allowances in Housing for Small and Backyard Poultry Flocks"

Applies to:

United States

Assumption:

The source gives no specific outdoor recommendation for ducks — it states plainly that the larger the run, the better, without a defensible minimum.

Calculation:

No calculation. Outdoor mode isn't given a headline figure rather than inventing one.

Stable space needed

Source:

British Horse Society, minimum stable dimensions

Applies to:

UK — BHS guidance, built on the same room-to-lie-down-rise-and-turn-around principle as DEFRA's statutory welfare code for horses

Assumption:

Published as a minimum by size band, not a single flat figure — a pony genuinely needs less floor than a large horse. Bands run pony, large pony, horse (up to 16.2hh) and large horse (over 16.2hh).

Calculation:

Band dimensions (3.05×3.05m pony, 3.05×3.65m large pony, 3.65×3.65m horse, 3.65×4.25m large horse) multiplied by horse count. Each horse is assumed to have its own stable, so this is per-animal floor area, not a shared-pen allowance.

Grazing / turnout land needed

Source:

British Horse Society, pasture management guidance

Applies to:

UK — permanent grazing

Assumption:

BHS publishes a range of 0.4–0.6 hectares per horse; we use the midpoint (0.5ha) as a single starting figure. It's only ever a starting guide — pasture quality, management and grazing hours all change the real figure for a given piece of land.

Calculation:

0.5 hectares (1.25 acres) per horse, multiplied by horse count.

Stall space needed, by size band

Source:

eXtension, "Equine Facilities: Stall Dimensions"; Penn State Extension, "Horse Stall Design"

Applies to:

United States — extension guidance; no federal or state law sets a minimum horse stall size. Added as a size band 2026-09-22, closing the gap the UK calculator's pony/horse/large-horse bands had no US equivalent for.

Assumption:

eXtension states 10×10ft as its minimum for riding horses (ponies "may be smaller, depending on breed", but no specific figure is given for them), 12×12ft as standard for a roughly 1,000lb horse (also Penn State's baseline, general rule "wall length is 1.5 times the horse's length"), and 16×16ft "or larger" for bigger horses. Penn State separately says to adjust for "significantly larger stall occupants" like draft horses without giving its own number — so the 16×16ft figure is eXtension's, not a joint one. This replaces the previous single flat 144 sq ft figure (the old UNL Extension 100–144 sq ft range, upper end used) with three real bands.

Calculation:

Band dimensions (10×10ft small/pony-type, 12×12ft standard, 16×16ft large/draft) multiplied by horse count, per horse.

Dry lot / turnout space needed

Source:

University of Minnesota Extension, horse dry lots and shelters guidance

Applies to:

United States — minimum exercise-lot recommendation

Assumption:

This is a minimum exercise/turnout lot, not a pasture-grazing figure, and doesn't include space for shelters, feeders or water troughs.

Calculation:

400 sq ft minimum per horse, multiplied by horse count.

Why there's no pasture-grazing figure here

Source:

University of Minnesota Extension guidance, cited in this calculator's own page copy

Applies to:

United States

Assumption:

The dry lot figure above is for exercise space, not for pasture that's meant to provide meaningful nutrition. Where pasture is a real feed source, extension guidance points to roughly 2 acres per 1,000lb horse on well-managed land, more on poorer soil — a different question from the dry lot/turnout figure this calculator gives.

Calculation:

No calculation shown as a headline figure. Visitors relying on pasture as a feed source are pointed to their local extension office rather than a single number, since land quality varies too much for one defensible figure.

Shelter floor space

Source:

Cornell Cooperative Extension, "Backyard Poultry and Livestock Density Recommendations" (May 2020)

Applies to:

No UK figure exists: the British Alpaca Society says only that a shelter must be large enough for all the alpacas in the field. Cornell's US extension figure is used as the nearest published number.

Assumption:

Cornell gives a minimum of 20 sq ft per alpaca for a permanent barn. Converted to 1.86m² per alpaca.

Calculation:

1.86m² (20 sq ft) per alpaca × alpaca count.

Grazing land

Source:

British Alpaca Society, "Accommodation"

Applies to:

UK — the national breed society's husbandry guidance

Assumption:

BAS says the stocking rate depends on the amount and quality of grass, and is typically 4 to 6 alpacas per acre. Shown as a range.

Calculation:

Alpaca count ÷ 6 to alpaca count ÷ 4 acres.

Minimum group size

Source:

British Alpaca Society, "Husbandry"

Applies to:

UK

Assumption:

BAS: alpacas are herd animals and should be kept in groups of 3 or more.

Calculation:

A warning shows below 3 alpacas. It doesn't change the area figures.

Barn floor space

Source:

Cornell Cooperative Extension, "Backyard Poultry and Livestock Density Recommendations" (May 2020)

Applies to:

United States — Cooperative Extension guidance; no federal or state law sets a minimum

Assumption:

A minimum of 20 sq ft per alpaca for a permanent barn, with a three-sided shed recommended for bad weather.

Calculation:

20 sq ft per alpaca × alpaca count.

Pasture

Source:

Cornell Cooperative Extension (as above); UMass Amherst Extension, "Alpaca Housing"

Applies to:

United States

Assumption:

Cornell gives 3 to 4 adult alpacas per acre. UMass Extension's rule of thumb is about 6 per acre depending on pasture quality, so Cornell's lower density is used as the planning range.

Calculation:

Alpaca count ÷ 4 to alpaca count ÷ 3 acres.

Minimum group size

Source:

British Alpaca Society; Rutgers Cooperative Extension

Applies to:

General — no US body sets a number

Assumption:

Rutgers says llamas and alpacas are social and do best pastured together; the British Alpaca Society gives the number, 3 or more.

Calculation:

A warning shows below 3 alpacas. It doesn't change the area figures.

Covered bedded area

Source:

The Donkey Sanctuary, "Stable measurement guide" (April 2023)

Applies to:

UK — guidance from the UK's main donkey welfare charity, for a standard-sized donkey

Assumption:

About 4.7m² (50 sq ft) of covered bedded area per donkey, 9.4m² for a pair. The guide adds that donkeys should ideally have more room to move around indoors if they can't go outside.

Calculation:

4.7m² per donkey × donkey count.

Grazing and turnout land

Source:

The Donkey Sanctuary, Rehoming Scheme terms and conditions

Applies to:

UK

Assumption:

A minimum of 0.5 acre (2,000m²) of suitable and safe grazing and/or exercise area is recommended for each donkey.

Calculation:

2,000m² (0.5 acre) per donkey × donkey count.

Company

Source:

The Donkey Sanctuary, Rehoming Scheme terms and conditions

Applies to:

UK

Assumption:

Donkeys form close bonds, so the Sanctuary normally rehomes them in pairs or small groups.

Calculation:

A warning shows for a single donkey. It doesn't change the area figures.

Covered bedded area

Source:

The Donkey Sanctuary, "Donkey Care Handbook" (5th edition, distributed in the US by ASPCApro)

Applies to:

No US government or extension figure for donkeys was found. The Donkey Sanctuary's handbook is written for owners worldwide.

Assumption:

About 50 sq ft of covered area per donkey, 100 sq ft for a pair.

Calculation:

50 sq ft per donkey × donkey count.

Grazing and turnout land

Source:

The Donkey Sanctuary, "Donkey Care Handbook"

Applies to:

General guidance

Assumption:

Approximately half an acre of suitable and safe grazing and/or turnout land for each donkey, depending on the land and grass.

Calculation:

0.5 acre per donkey × donkey count.

Company

Source:

The Donkey Sanctuary, Rehoming Scheme terms and conditions

Applies to:

General

Assumption:

Donkeys form close bonds, so the Sanctuary normally rehomes them in pairs or small groups.

Calculation:

A warning shows for a single donkey. It doesn't change the area figures.