Plan on one nest box for every four or five hens, and 6 to 10 inches of roost bar for each bird. For ten standard hens that is three or four boxes and 60 to 100 inches of roost. Enter your flock below and the calculator returns box count, box size, mounting height, roost length and bar count, and shows where the extension services disagree.
Three extension sources feed it: Oregon State University Extension (publication EC 1644), Penn State Extension’s small-scale poultry housing table and Utah State University Extension’s backyard housing page. Where they differ, the tool shows all three instead of picking one quietly.
How many nest boxes per chicken
The ratio is not one number, and the spread matters once your flock passes eight.
- Utah State: one box per 4 to 5 hens.
- Oregon State: one box for about every four birds.
- Penn State: two nests for the first four hens, then one more for every four additional.
| Hens | USU (per 5) | OSU (per 4) | Penn State | We recommend |
|---|---|---|---|---|
| 4 | 1 | 1 | 2 | 2 |
| 6 | 2 | 2 | 3 | 3 |
| 10 | 2 | 3 | 4 | 4 |
| 12 | 3 | 3 | 4 | 4 |
| 20 | 4 | 5 | 6 | 6 |
| 25 | 5 | 7 | 8 | 8 |
We recommend the highest of the three, because an extra box costs a few dollars in plywood and a missing one costs eggs on the floor. At six hens the Penn State count is three, and our 6x8 coop carries three; at its top rating of nine hens Penn State would want four, so that coop is one box short by the strictest rule. Penn State counts two boxes as the starting point, so even three or four hens get two.
Box size and height
Oregon State’s EC 1644 gives 12 inches deep, 12 wide and 12 tall for a standard box, and Penn State agrees on 12 by 12 as a minimum with larger boxes for bigger birds. USU’s range is 12 to 15 inches in height and width and at least 12 deep. The calculator returns 12 by 12 by 12 for bantam and standard hens. For large or heavy breeds it returns 14 by 14 by 14, which sits inside USU’s range; no extension service publishes a breed table, so that figure is our choice.
Mounting height has three answers that fit together: USU wants the floor at least 18 inches up, Penn State says two feet or more, and Oregon State says never lower than the roosting poles, which keeps boxes cleaner. The tool says 18 to 24 inches, and our nest bank uses 24.
How much roost space per chicken
Oregon State says 5 to 10 inches of pole per bird. USU says 6 to 10. Penn State says 6 inches for standard chickens and 4 for bantams. The calculator returns a low and a high for your hens: bantams 4 to 6 inches, standard 6 to 10, and 10 for large or heavy birds, the top of both the Oregon State and USU ranges. Our plans allow 10 inches a bird at the top of each design’s rated flock, so the roost column in any plan table is a ceiling, not a minimum.
Bars come next. Oregon State sets the poles 2 feet off the floor with 10 inches between them and builds them from 1- to 2-inch square lumber with the top edges rounded, because poles too small or too round can cause foot problems. USU keeps bars 14 inches apart and the perch at no more than about 3 feet, with 12 inches of clearance underneath. Enter the usable bar length for your coop and the tool divides the total roost length by it.
The droppings board is our arithmetic, not a published figure: the bar length times the bar spread plus two inches, in square feet.
A worked example
Ten standard hens with 60 inches of usable bar and bars 14 inches apart. Boxes: USU 2, Oregon State 3, Penn State 4, so we recommend 4. Roost: 60 inches at 6 per bird and 100 at 10 per bird. That is one 60-inch bar at the low end and two at the high end. Six hens come out at 2, 2 and 3 boxes, 12 large hens need 120 inches or two bars of 60, and 25 hens need 5, 7 or 8 boxes. We computed these in Python from the rules above.
What our coops already include
| Design | Rated hens | Boxes | Hens per box at the top | Roost allowance |
|---|---|---|---|---|
| 4x4 starter coop | 2-3 | 2 | 1.5 | 30 in |
| 4x8 shed coop | 4-6 | 2 | 3.0 | 60 in |
| 6x8 chicken coop | 6-9 | 3 | 3.0 | 90 in |
| 6x8 walk-in shed coop | 7-10 | 3 | 3.3 | 100 in |
| 8x12 walk-in shed coop | 14-18 | 5 | 3.6 | 180 in |
| 8x16 walk-in shed coop | 19-26 | 7 | 3.7 | 260 in |
Every one stays under four hens a box at its top rating, which meets Oregon State’s ratio and USU’s. Penn State’s count is stricter above eight hens, and by it the 4x8 shed at six hens, the 6x8 chicken coop at nine, the 6x8 walk-in at ten, the 8x12 walk-in at 18 and the 8x16 at 26 are each one box short at the top of their range. Add a box or a nest bank if you run a flock that large and want Penn State’s margin. The size chart lists the whole line, and our interior layout guide shows where roost, boxes and droppings board sit relative to each other. For a deeper dive on bar profiles and mounting, see the roost plans guide.
The 3-box nest bank
If your coop came with too few boxes, our 3-box nest bank is a standalone bank rated for up to 12 hens at four to a box. It costs $240-$330 in materials and is a 3 to 5 hour build, bedded or roll-out. The bank is 39 inches wide and 16 deep; each box opening is 10 inches high and 12 wide and the dividers sit about 12-3/4 inches apart, which is a standard-breed size. If you keep heavy breeds and the calculator returns 14 inches, check the opening before you build. Mount it 24 inches up, on studs: loaded with bedding and hens it comes to about 111 lb. The nesting box guide covers bedding and cleaning, and the bank’s own page has the cut list.