Chicken Coop Size Calculator
Not sure how big a coop your flock needs? This free chicken coop size calculator tells you exactly how much interior coop space, outdoor run space, roost bar length, and how many nesting boxes your hens need — based on your flock size and breed type. Results update instantly as you type.
Enter your flock
Bantams are small breeds; large breeds include Orpingtons, Brahmas, and Jersey Giants.
The breed selector sets these to standard guidelines (bantam 2/5, standard 4/10, large 6/12 sq ft). Adjust them freely if you want more generous space.
Your results
Estimates based on common welfare guidelines (not regulations). Round up when building — extra space is always better for the birds.
How to use this calculator
Enter the number of hens in your flock and pick a breed size — bantam, standard, or large. The calculator instantly shows the minimum coop interior space and outdoor run space your flock needs, plus a suggested coop footprint, total roost bar length, and the number of nesting boxes.
The breed buttons set the per-hen space to widely used guidelines (2/5 sq ft for bantams, 4/10 for standards, 6/12 for large breeds). You can override the per-hen values in the two number fields if you want to plan a roomier setup — many keepers add a buffer for harsh weather or future flock growth.
How it works
The math is simple multiplication. Coop interior space = number of hens × coop sq ft per hen. Outdoor run space = number of hens × run sq ft per hen. The suggested coop dimensions are the smallest rectangle (kept to a reasonable shape, no side more than 3× the other) whose area meets or exceeds the required square footage.
Nesting boxes follow the one-box-per-3-to-4-hens rule: boxes = ceil(hens ÷ 4), rounded up. Total roost bar length = hens × 8 to hens × 10 inches. These are welfare guidelines shared by backyard-chicken keepers and extension services — not legal regulations. Local rules on flock size and setbacks vary, so check your city or HOA before building.
Frequently asked questions
How much coop space does each chicken need?
The widely used welfare guideline is about 4 square feet of interior coop space per standard hen. Bantam (small) breeds need roughly 2 square feet each, and large heavy breeds need 5 to 6 square feet each. These are welfare guidelines, not legal requirements.
How much outdoor run space does each chicken need?
A common guideline is about 10 square feet of outdoor run space per standard hen — roughly 5 square feet per bantam and 12 square feet per large breed. More run space means less crowding, less pecking, and happier birds.
How many nesting boxes do I need for my hens?
Plan on one nesting box for every 3 to 4 hens. Hens happily share boxes, so you don't need one per bird: a flock of 6 hens needs 2 boxes, and a flock of 12 needs 3 to 4.
How much roost bar space does each chicken need?
Allow 8 to 10 inches of roost bar length per hen, measured edge to edge. For example, 6 hens need 48 to 60 inches of total roost space. Mount roosts at least 18 inches above the floor and keep them level so birds don't fight for the highest spot.
Are these coop size numbers regulations or just guidelines?
They are welfare guidelines used by backyard-chicken keepers and extension services, not universal legal regulations. Some cities and homeowner associations do have their own minimum space rules or flock-size limits, so check your local ordinances before building.