Size by flock
Coop size for 20 chickens
For 20 standard-size hens: 80 sq ft of floor (7.4 m²), a 200 sq ft run (18.6 m²), 200 inches of roost and 5 nest boxes. Here is what that looks like in practice.
The plan
| Item | Minimum | Suggested shape |
|---|---|---|
| Coop floor | 80 sq ft · 7.4 m² | about 8.9 × 8.9 ft (2.7 × 2.7 m) |
| Run | 200 sq ft · 18.6 m² | about 10 × 20 ft (3.0 × 6.1 m) |
| Roost bar | 200 in · 5.1 m | a 16.7 ft 2×4, wide side up |
| Nest boxes | 5 | 12 × 12 in |
| Feeders and waterers | 2 of each | one extra waterer in summer |
Why these numbers
They are the minimums extension offices and most experienced keepers use: 4 sq ft of coop and 10 sq ft of run per standard hen, 8 to 10 inches of roost, one nest box per 3 to 4 hens. A crowded coop is the number one cause of feather picking, bare backs and broken eggs.
If your hens are not standard size
Bantams (Silkies, Sebrights): 40 sq ft of coop and 120 of run. Large breeds (Orpington, Brahma, Jersey Giant): 100 and 240.
Before you build
- Ventilation up high, no drafts down low. Half-inch hardware cloth on every opening, never chicken wire.
- Roosts higher than nest boxes, or they will sleep in the boxes and foul the eggs.
- A walk-in coop saves your back every single week.
- Build for 22: chicken math is real.
- Check your city and HOA rules on flock size and setbacks before buying lumber.
Half-inch hardware cloth keeps out what chicken wire can’t. It’s sold by the roll, so measure every opening first.
Paid link Half-inch hardware cloth on Amazon →
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Change the breed or the count in the coop size calculator.
Common questions
What size coop do I need for 20 chickens?
At least 80 sq ft of floor (7.4 m²) for standard breeds, plus a 200 sq ft run (18.6 m²). More is always better.
How many nest boxes for 20 chickens?
5. One box per 3 to 4 hens; they will all use the same one anyway.
Can 20 chickens live in the coop with no run?
Only if the coop is sized as coop and run combined, about 280 sq ft, with light and ventilation. A 80 sq ft coop is a bedroom, not a home.
What about bantams or large breeds?
Bantams: 40 sq ft of coop and 120 of run. Large breeds (Orpington, Brahma): 100 and 240.