I recently shipped FlockCalc , a small site of free calculators for people who keep chickens, quail and ducks in their backyard. No accounts, no ads — just instant answers.

The interesting part wasn't the code, it was the maths arguments. Ask ten chicken keepers how much coop space a hen needs and you get ten answers. I ended up using the university extension figures: about 3.5 sq ft of coop and 10 sq ft of run for a standard hen, 2/6 for bantams, 4.5/12 for large breeds, 10 inches of roost per bird, and one nesting box per four hens.

That means the classic 4 × 8 ft coop honestly holds about 9 standard hens — not the 16–20 the box claims.

The most-used tool so far is the chicken coop size calculator .…