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About

A coop sized for your flock

Most coop plans come in one size and promise a number of hens the floor cannot hold. The Coop Planner starts from your flock: it works out the floor, nest boxes, roost and vents the hens need, frames a coop that provides them, and shows each check in green, amber or red.

How it works

  1. 1

    You set the flock

    How many hens, what size of bird, and whether they have a run or stay in.

  2. 2

    It sizes the coop

    Floor, nest boxes, roost length, vents and the pop door, each checked against the flock.

  3. 3

    It frames the coop

    Walls stud by stud on 4x4 legs, the roof, the nest boxes, roosts and every opening screened with hardware cloth.

  4. 4

    It counts the materials

    Lumber packed onto standard boards, sheets, hardware cloth by the roll, fasteners and hardware.

The method

Every rule in the planner comes from a US university extension publication we read in full. Where the sources disagree, and on space they do, we take the most recent revision, check that at least two sources support it, and pick the value that gives a coop that does not fail the people who build it. Virginia Tech raised its space figures in 2023; older tables that other calculators still quote are lower.

Each check has a default and a minimum. Green meets our default. Amber sits between the smallest figure an extension source accepts and our default, so we never fail a design that an extension service would approve. Red is below every source we read.

Where the sources give a range, say nothing, or only cover standard laying hens, we chose a value and call it our default: the 24 inch floor height, the 36 and 72 inch walls, and the bantam and large breed figures scaled from the standard ones. No extension publication we read gives a ventilation area in numbers, so the vent check uses the rule of thumb most coop builders use and only ever turns amber.

What it is not

The Coop Planner is a planning aid. It is not veterinary advice, it does not know your climate, predators or local rules on keeping poultry, and it is not a substitute for your building department. Check the plan against your local rules before you build.

The designer, the calculators, the free plans and the guides cost nothing and need no account. What pays for them is the builder's plan: a PDF for the exact coop and run you design, with every wall framed, every cut listed and a step-by-step build, for $29 once. If our plan has an error, we fix it or refund you. The site carries no advertising, and no item is in a plan because someone pays us for it.

Who runs it

The Coop Planner is an independent project operated by Westernmost LLC, 32 N Gould St, Sheridan, WY 82801, USA. If you find a mistake in a rule or a number, please tell us: a fix to the engine fixes every coop at once.

Sources

Read on October 8, 2026.

Shown for comparison only, never as proof:

See the sizes for your flock

Coop size by flock