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FurCalc

Chicken Coop Size Calculator — Coop, Run, Nesting Boxes & Roost

How big should your chicken coop and run actually be? This calculator sizes the indoor coop, the outdoor run, the number of nesting boxes, and the roosting bar length for any flock size and breed mix — standard hens, bantams, dual-purpose, or heavy meat breeds. Square-footage minimums follow the USDA backyard poultry husbandry guidance with Backyard Chickens forum consensus for the welfare-tier “recommended” sizing.

Calculator

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Coop (indoor/roosting)
24 ft²
4 ft² per bird
Run (outdoor/fenced)
60 ft²
10 ft² per bird
Nesting boxes
2
1 per 3-4 hens
Roosting bar
4.5 ft
9″ per bird
Free-range: add 250 ft² per bird for ideal foraging. Undersized coops cause stress, pecking and egg drop.

Standard hen vs bantam vs heavy breed: how do coop minimums differ?

Breed classCoop ft² / birdRun ft² / birdRoost length
Standard hen (Leghorn, Plymouth Rock)4 ft²10 ft²9 in / bird
Bantam (Silkie, Sebright)2.5 ft²7 ft²6 in / bird
Heavy (Jersey Giant, Brahma)5-6 ft²12-15 ft²12 in / bird
Dual-purpose (Orpington, Wyandotte)4-5 ft²10-12 ft²10 in / bird

Coop terminology

Roost / perch
Elevated bar where hens sleep. 9 inches per standard bird, 2-4 ft off the floor.
Nesting box
Enclosed laying space — one box per 3-4 hens, raised off the floor.
Pecking order stress
Aggression that escalates when hens are overcrowded; the leading reason to over-size the run.

Frequently Asked Questions

How much space does a chicken need?

Standard chickens: 4 sq ft in the coop + 10 sq ft in the run per bird. Bantams: 2.5 + 7 sq ft. Free-range birds ideally have 250 sq ft per bird but still need a safe coop at night.

How many nesting boxes do I need?

1 nesting box per 3-4 hens. Standard box: 12″ × 12″ × 12″. More boxes don't necessarily mean more eggs — hens often share favorite boxes.

How long does a roosting bar need to be?

9 inches of roosting bar per standard chicken (6" for bantams). Bar should be 2-4 inches wide (they sleep with feet flat), positioned higher than nest boxes to discourage sleeping in boxes.

What happens if my coop is too small?

Overcrowding causes stress, pecking, egg-eating, feather-plucking, disease outbreaks and decreased egg production. Add space or reduce flock size before behavior worsens.

Sources & References

  1. [1]
    Chicken Coop Sizing — Backyard Chickens community
  2. [2]
  3. [3]

Common mistakes to avoid

  • Ignoring climate — 4 sq ft/bird is fine in Florida; Maine chickens need 6-8 sq ft because winter days confine them indoors.
  • Stacking too many hens — overcrowding causes pecking, egg-eating, and disease spread.
  • Inadequate ventilation — ammonia buildup damages respiratory systems; need vents near the roof without direct drafts.

When to call the vet immediately

  • Hen stops laying suddenly mid-season and sits puffed up — could be egg-bound (life-threatening within 24-48h).
  • Multiple hens with gasping/mouth-breathing — possible Mycoplasma or Infectious Bronchitis outbreak.

Pro tips

  • Add one nest box per 4 hens (not 1 per hen — they share).
  • Roost 8-12 inches per bird, higher off floor for heavier breeds.
  • Use deep-litter method in cold climates — insulation + composting heat.