Outdoor hen run sizing

Chicken Run Area Calculator

Work out outdoor run area, space per hen, shortfall, perimeter mesh and covered area for a small flock, with allowances for breed size and future birds.

Enter Run And Flock Details

Flock Hens using the run Count adult birds sharing this outdoor space. hens Run space allowance Use your own standard. More space is better for grass, enrichment and lower stress. m2/hen Future hens Optional birds you plan to add later. hens

Run shape Run length Measure the usable inside length. m Run width Measure the usable inside width. m Mesh height Used to estimate side mesh area for a rectangular run. m

Weather and build Covered share of run Roofed or sheltered area for rain, shade and housing-order periods. % Gate and overlap mesh allowance Extra mesh for joins, buried skirt, gate waste and errors. % Lost area for feeders and features Dust bath, feeders, water stands, shrubs or raised platforms. %

Run Area Result

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Enter dimensions and flock size to see the fit.

Run Snapshot

Outdoor area does not replace a dry, secure coop. Check welfare guidance, local rules and avian influenza housing updates.

What The Run Area Needs To Do

A chicken run is the daytime outdoor or covered space where hens forage, scratch, dust bathe and move away from each other. It is different from the coop. The coop is for shelter, roosting and laying; the run is where the flock spends active time. A run that is too small can quickly become bare, muddy and stressful. Even where birds have some supervised free ranging, the fixed run still matters on wet days, during predator pressure and during periods when birds must be kept under cover.

This calculator lets you choose a square-metre allowance per hen rather than pretending there is one perfect number. Small-flock advice varies, and welfare depends on design as well as area. A run with dry cover, perches, dust bath, shade, feeders, water and visual barriers can work better than a larger empty pen. The calculator therefore shows usable area after lost-space allowance, not only the outside rectangle.

Measuring A Chicken Run

Measure inside the fence line. If the run is not a rectangle, split it into rectangles or triangles and add the areas, then enter the closest equivalent length and width. Do not include permanently blocked areas under storage, solid ramps or inaccessible corners. If feeders, shrubs or a dust bath take a large part of the run, use the lost-area field. Those features can improve welfare, but they reduce open floor area.

For mesh, the calculator uses a rectangular perimeter. Real builds need more: overlaps, buried skirt, roof fixing, gate frames, uneven ground and mistakes. Add a mesh allowance before ordering. If foxes, rats or badgers are a risk, ordinary lightweight netting may be unsuitable. Security matters as much as the area number.

Formula And Method

Planning hens = current hens + future hens Required run area = planning hens x chosen m2 per hen Usable run area = length x width x (1 - lost-area percentage) Mesh area = 2 x (length + width) x height x (1 + mesh allowance)

The result rounds run area to two decimals and mesh area to one decimal. It also calculates the maximum hens that fit the usable area at your chosen allowance. This is a space planner, not a permit, welfare certificate or disease-control answer. If local rules, allotment rules, tenancy terms or animal-health notices apply, those controls sit outside this arithmetic.

Worked Run Examples

Six hens in a 4 m by 3 m run

The outside area is 12 m2. If 8 percent is lost to feeders and features, usable area is 11.04 m2. At 2 m2 per hen, six hens need 12 m2, so the run is close but slightly short.

Covered winter run

A roofed run can keep bedding drier and help during housing measures. The covered percentage helps you check whether shelter is a token corner or a meaningful part of the birds’ usable space.

Future hens

Adding two future hens may turn a comfortable run into a tight one. Plan the run for the flock you expect, not only the birds arriving this week.

Run Design Checks

Run feature	Why it matters	Planning tip
Dry covered area	Wet mud and damp bedding raise welfare and parasite concerns.	Roof a meaningful share of the run or use a covered section with dry litter.
Dust bath	Dust bathing is a natural behaviour and helps feather condition.	Keep it dry and count the space in the lost-area field if it is fixed.
Perches and platforms	Height gives interest and escape space for lower-ranking birds.	Use stable, safe heights and avoid sharp edges.
Predator mesh	Foxes and rats exploit weak mesh, gaps and soft ground.	Use suitable welded mesh, secure fixings and a buried or outward skirt where needed.
Ground rotation	Grass can be stripped quickly in a small fixed run.	Moveable runs or woodchip areas may help manage mud and bare ground.

Run Area And Behaviour

Area is only part of welfare. A plain square pen can still lead to feather pecking or bullying if there is nowhere to hide, perch or forage. Add visual breaks such as branches, safe shrubs, low partitions or platforms so birds can move away from each other. Keep feeders and drinkers placed so dominant hens cannot block access.

When To Expand The Run

Expand the run if the ground is constantly bare and muddy, if birds queue at the pop-hole, if bullying rises, if there is not enough covered space during bad weather, or if the flock size is likely to grow. It is usually easier to build a larger secure run at the start than to patch small extensions onto weak mesh later.

FAQs

How much outdoor run space does a chicken need?

Advice varies by system and flock. Pick a generous m2-per-hen allowance, then check design, cover, enrichment and ground condition. More space is usually better.

Can the coop count as run space?

No. Coop space and run space have different jobs. The coop is for shelter, roosting and laying; the run is for daytime movement and behaviour.

How much of the run should be covered?

There is no single rule for every garden, but a meaningful covered area helps with rain, shade and disease-control housing periods. The calculator shows the covered square metres.

Does a bigger run stop all bullying?

No. Space helps, but flock mix, perches, feeders, health, introductions and visual barriers also matter. Severe pecking needs prompt action.

Is this calculator welfare advice?

It is a planning tool. Use official welfare guidance and veterinary or poultry-specialist advice for health, injury or behaviour concerns.

Sources

Department for Environment, Food and Rural Affairs. (2023). Code of practice for the welfare of laying hens and pullets. GOV.UK. https://www.gov.uk/government/publications/poultry-on-farm-welfare/poultry-welfare-recommendations
RSPCA. (2026). Tips for housing and outdoor space for pet chickens. https://www.rspca.org.uk/adviceandwelfare/farm/farmanimals/chickens/environment
Animal and Plant Health Agency. (2026). Avian influenza: rules, guidance and disease prevention. GOV.UK. https://www.gov.uk/guidance/avian-influenza-bird-flu