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Coop & Clutch

Coop size calculator

Your flock in, the floor area, run, roost bar and nest boxes it needs out - with the arithmetic shown rather than hidden.

This is the calculation every page on Coop & Clutch runs in reverse. Here you start from your birds and get the space they need; on a coop page we start from the published dimensions and tell you how many birds they support. Same constant, same arithmetic, both directions.

Your flock

Add two or three for the birds most people acquire in the first year.

Most backyard breeds - Rhode Island Red, Australorp, Leghorn

Outdoor access

Birds with no outdoor space need roughly double the indoor floor, because the coop is the whole of their world.

6 birds needs

Coop floor
24sq ft
Run floor
48sq ft
Roost bar
48inches
Nest boxes
2boxes

The working

6 birds x 4 sq ft = 24 sq ft of coop floor, plus 48 sq ft of run. Roost bar at 8 in a bird = 48 in. Nest boxes at one per four hens = 2.

That coop floor is roughly 4.9 ft square, or 6.0 ft by 4 ft. Compare it against the published dimensions of any coop you are considering - multiply length by width in inches and divide by 144.

Now check a real coop: the ranked list shows every coop’s measured floor area beside its claim, or start from your flock size.

Where these figures come from

The per-bird floor figures come from published extension-service guidance, which gives a range of 3 to 5 square feet of indoor space per bird for backyard flocks. We use 4 as the midpoint for standard hens, 2 for bantams and 5 for large fowl - the ends of the same range. Run area is roughly double the indoor figure, roost bar is 8 inches per standard bird, and nest boxes are one per four hens, which is the conservative end of the published one-per-four-to-five.

The full reasoning, including what happens when a manufacturer publishes nothing usable, is on the methodology page.

The reference table

The same figures for the most common flock sizes, for standard-size hens with run access - so the answer is on the page whether or not you use the calculator above.

Standard laying hens with outdoor run access
HensCoop floorRun floorRoost barNest boxes
28 sq ft16 sq ft16 in1
312 sq ft24 sq ft24 in1
416 sq ft32 sq ft32 in1
624 sq ft48 sq ft48 in2
832 sq ft64 sq ft64 in2
1040 sq ft80 sq ft80 in3
1248 sq ft96 sq ft96 in3
1560 sq ft120 sq ft120 in4
2080 sq ft160 sq ft160 in5

What to do with the number

  1. Take the coop floor figure and compare it against a listing’s published length and width, multiplied and divided by 144.
  2. If the listing quotes a whole-unit footprint including an attached run, treat your comparison as generous - the enclosed henhouse is smaller.
  3. Check the roost bar figure too. Most coops supply far less than 8 inches per bird, which is why birds end up sleeping in the nest boxes.
  4. Ignore the box count in the listing. One per four hens is the guidance and coops routinely ship double, at the cost of floor area.
  5. Start from your flock size, where the roundups already show measured area against every maker’s claim.

About this calculator

+How does this chicken coop size calculator work?
It multiplies your bird count by the published per-bird floor figure for that size class - 2 square feet for bantams, 4 for standard hens, 5 for large fowl - and doubles it if the birds have no outdoor run. Run area, roost bar and nest boxes come from the same published guidance. The working is shown so you can check it.
+How big a coop do I need for 6 chickens?
About 24 square feet of coop floor for six standard hens, plus roughly 48 square feet of run, 48 inches of roost bar and two nest boxes. Almost nothing sold as a six-bird coop measures 24 square feet of enclosed floor. Coops for 6 chickens.
+Why does the number go up when I say coop only?
Because the coop becomes the entire environment - where the birds eat, dust bathe, get away from each other and pass twelve hours of daylight. Published guidance moves up accordingly, to roughly double the figure used when birds have run access.
+How do I compare this to a coop I am looking at?
Take the listing's published length and width in inches, multiply them, divide by 144. That gives square feet, and you can compare it directly with the coop-floor figure here. If the listing only gives a whole-unit footprint including a run, your answer is a generous upper bound. The full method.
+Should I size for the flock I have or the flock I will have?
The one you will have. Most people add two or three birds in the first year - a neighbor rehoming, a straight-run chick that turns out fine, a friend's flock breaking up. Buying one size class up costs less than buying twice.