Chicken Coop Size Calculator
Coop floor area, run space, roost length, and a footprint for your flock, from extension-service guidance. The math runs in your browser and nothing is uploaded.
The method
- Interior floor space follows the housing style. Penn State Extension's small-flock guide gives 2 square feet per bird inside when the birds use an outdoor run, and its laying-flock guide gives 5 square feet per hen when the birds stay inside.
- Run space is reported from 5 square feet per bird, the extension minimum, up to 10 square feet per bird.
- Roost length is 6 inches per bird, converted to feet.
- The footprint maps the required area onto your chosen width and rounds the length up to the next whole foot, so the build never comes out small.
How to use
- Enter how many full-size chickens you keep, from 1 to 50.
- Pick the housing style: a coop with an outdoor run, or a coop the birds stay inside all day.
- Optionally enter the coop width you have in mind, and the calculator gives a matching interior length in whole feet.
- Build or buy to at least the sizes shown, then watch the flock: feather picking or crowding at the door means more space is needed.
Frequently asked questions
Is anything I enter uploaded or stored?
No. The flock size and housing choices are used inside your browser tab and the math runs there. Nothing is sent to a server, nothing is saved on our side, and nothing is written to your browser's storage. The site sets no cookies and has no accounts; if an ad is shown, the ad network follows its own policies but never receives what you typed.
Where do the space numbers come from?
From Penn State Extension. Their small-flock guide sets indoor coop space at 2 square feet per bird when the birds have an outdoor area, and their laying-flock management guide sets 5 square feet per hen for birds kept inside, with an exercise area of 5 to 10 square feet per bird. Roost length is 6 inches per bird in both guides, and nests are at least 12 by 12 inches.
I have heard 3 to 4 square feet per bird inside. Which is right?
Published guidance varies: some sources give more interior room than Penn State's 2 square feet with outdoor access, and others give less. Treat the calculator's numbers as a floor, not a target. Extra space is always safe for the birds, and in a climate where the run turns to mud for part of the year, building bigger inside pays off.
What about bantams?
Bantams are much smaller than full-size birds and many keepers size down for them. This calculator sizes for full-size chickens, so a bantam flock gets extra room, which does the birds no harm. If you keep both, size for the full-size birds.
How many nest boxes do I need?
Hens share. The guidance used here specifies nests at least 12 by 12 inches with a few inches of clean shavings, and a small flock usually gets by on a handful of boxes rather than one per bird. Place them off the floor, away from the roosts, with the darkest corner you can offer.
How should the roosts be set up?
Penn State Extension allows 6 inches of roost length per bird, places roosts 18 to 24 inches above the floor, and spaces them about a foot apart, away from the nests. A lower second roost helps heavier breeds get down safely.