Chicken Coop Size Calculator
Enter your flock size to get the coop floor area, run area, nest boxes and roost length you need. Crowding is the single biggest cause of pecking and disease.
Why the space numbers matter
- 2 sq ft inside is the absolute minimum for a healthy bird in a mild climate
- 8 sq ft in the run prevents boredom, which is what causes feather-pecking
- If birds are shut in all winter, use the generous setting — they cannot escape each other
- Bantams need about two-thirds of the space of a standard hen
Height and ventilation
A coop should be at least 60 cm / 2 ft tall at the back and higher at the front. Height matters less than airflow: a sealed coop builds up ammonia and moisture, which causes respiratory disease.
Leave vents high on the wall, above the birds' heads when roosting. Ventilation without draught at bird level is the goal.
Run vs free range
The calculator assumes the birds are confined. If they genuinely free-range over a large area for most of the day, the run can be smaller — but a "run" they are shut into on wet days still needs the full space.
Common questions
How big should a chicken coop be for 4 hens?
About 1.1 m² (12 sq ft) of floor space inside, plus roughly 3.7 m² (40 sq ft) of run. Add one nest box and about 90 cm of roost bar.
How many chickens can fit in a 4x8 coop?
A 4x8 ft coop is 32 sq ft, so about 10 hens at 3 sq ft each — but only if they also have at least 80 sq ft of run.
Can chickens be kept in a small coop permanently?
Not healthily. Crowding causes pecking, feather loss and disease. If space is limited, keep fewer birds rather than squeezing more in.
How much roost space per chicken?
About 20-25 cm (8-10 inches) of roost bar per bird. They shuffle for position, so a little extra prevents squabbles.
Coop plans, breeds, feeding amounts and the whole first year: Backyard Chickens for Beginners.
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