Chicken Coop & Run Size Calculator

How this calculator works

The calculator multiplies your flock size by a space allowance per bird. It uses 4 square feet of coop floor and 10 square feet of run for a standard-size hen, which are widely repeated minimums in extension poultry guidance. Bantams get about half of that, and large or heavy breeds get about 25 percent more. If your birds range freely for most of the day, the run figure drops, because the run then serves as shelter on bad days instead of daily living space.

A worked example

Six standard hens that are confined to a run need a coop of at least 24 square feet (for example 4 feet by 6 feet) and a run of at least 60 square feet (for example 6 feet by 10 feet). They need 2 nest boxes, about 5 feet of roost bar at 10 inches per bird, and roughly 6 square feet of ventilation opening.

What the other numbers mean

• Nest boxes: hens share them, so one box for every four or five hens is usually enough. They prefer a dark, quiet corner.
• Roost bar: hens sleep side by side on a wide, flat or rounded bar. Heavy breeds need sturdy, lower bars to avoid foot injuries.
• Ventilation: a coop must breathe even in cold weather to remove moisture and ammonia. Vents should be high up so that cold air does not blow directly over the roosting birds.

Where these numbers come from

Space allowances follow common extension and poultry-keeping guidance, which varies by source and climate, so check your local extension office. Ventilation and nest box ratios are widely used rules of thumb. Local zoning may also set minimum distances and maximum flock sizes, which these figures do not cover.