Advanced options
Start with at least 3 hens (they're flock animals) and buy the coop for the flock you'll END with: chicken maths only goes up. Manufacturers' "sleeps 6" claims run optimistic: measure the floor. Fox-proofing means weld mesh (not chicken wire, which foxes open), buried or skirted 30cm, and a latch a fox can't flip.
What The Chicken Coop Calculator Works Out
- Coop floor space: hens x 0.35 m2 of floor inside the house for sleeping and laying. Allow 0.3 to 0.4 m2 per standard hen; the flat-pack market's "sleeps six" claims routinely assume less, so measure the floor rather than trusting the label.
- Run space: 1 m2 per hen is the floor and 2 m2 the standard worth building to. Overcrowding is the root cause behind most feather-pecking, mite load and squabbling. The area under a raised coop counts toward the run and gives the shade and dust-bath corner hens use most.
- Fittings: 25 cm of perch per bird and one nest box per three hens, plus a feeder and drinker sized for a day away. Height matters far less than floor: chickens are walkers, not climbers.
- Breed size (advanced): scales every space figure. Bantams need roughly 70% of a standard hen's space; large and heavy breeds such as Brahmas need about 30% more floor and perch.
- Space per hen (advanced): edit the 0.35 m2 indoor and 1 m2 run assumptions directly, for example 0.5 m2 inside if the hens will be shut in during avian-flu housing orders, or 3 m2 or more of run if the ground is to stay grass rather than mud.
- Run footprint (advanced): the side length of a square run at the "far better" size, as a quick check against the space available in the garden.
- Feed per week and per year (advanced): a laying hen eats about 120 g of layers pellets a day, so four hens get through 3.4 kg a week and roughly nine 20 kg bags a year. The cost card uses your bag price (GBP 12 to GBP 16 is typical); treadle feeders and swept spills keep the rats off the bill.
- Eggs per week and feed cost per dozen (advanced): hybrids lay about five eggs a week in their first two years, pure breeds fewer and with a winter pause. Dividing the annual feed bill by the eggs gives the feed cost per dozen, usually GBP 1.50 to GBP 2.50 against GBP 3 to GBP 4 for shop free range, before bedding, the coop itself and the odd vet visit.
- Fox-proofing and registration: weld mesh rather than chicken wire, skirted or buried 30 cm, with latches beyond a clever paw; an automatic door is the hobby's best upgrade. All kept birds must now be registered with APHA's poultry register, and back-garden hens are legal in most of Britain subject to deed covenants and allotment rules.