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Calculators for chicken keepers

Work out how many hens your coop and run can hold, how much feed to buy, how much water to keep ready and how many nest boxes and roosts to build. Results update instantly and stay in your browser.

Piotr MarkotPiotr Markotpoultry keeper and calculator author

Do the maths before you buy or build

A calculator cannot see your hens' temperament or the mud after a wet November. It can give you an honest starting point, show the assumptions and let you change them. That is more useful than the optimistic flock size printed on a flat-pack coop.

How many chickens will fit in the coop and run?

Enter usable indoor floor area, excluding nest boxes, and the outdoor area the birds can actually use. The tighter space sets the limit.

These figures are for average adult hens. Leave more room for heavy breeds, a rooster, flock introductions and long periods indoors. Run area is a practical planning assumption, not a universal legal rule.

Your current space is a practical starting point for

15hens
Coop limit30 hens
Run limit15 hens
Coop needed for planned flock4 m²
Run needed for planned flock40 m²

The run is the bottleneck. A larger coop alone will not increase a sensible flock size.

max. hens = lower result from coop ÷ m²/hen and run ÷ m²/hen

How much feed do chickens need and what will it cost?

Calculate daily and monthly use, spillage allowance and the number of whole bags you need to buy.

Adult laying hens commonly eat about 100-120 g.

A daily allowance of 115 g is a sensible starting point for an adult layer, not a rigid rule. Body size, cold weather and feed energy density all change intake. Watch body condition and check whether feed is being left behind.

Feed needed for the full period, including allowance

37.3kg
Daily for the flock1.15 kg
Whole bags to buy2 × 25 kg
Cost of whole bags
Feed left after the period12.7 kg

kg = hens × days × g/day ÷ 1000 × (1 + allowance %)

How much water should you prepare for the flock?

Water disappears faster than expected, especially in hot weather. Calculate daily use, the full period and a two-day emergency reserve.

This is water to have available, not a promise that every millilitre will be drunk. Add a margin for spills, provide clean water at all times and check drinkers several times a day in hot weather.

Water needed for the selected period

21litres
Daily for the flock3 l
Tank refills3 × 10 l
Two-day emergency reserve6 l
Per hen over the period2.1 l

A drinker in direct sun, a leak or hens scratching dirt into it will increase real use. A calculator never replaces a daily water check.

litres = hens × days × litres per hen per day

How many nest boxes and how much roost space?

Every hen should fit on the roost at the same time, and there should be enough nests to avoid a morning queue at one box.

A practical choice is 4-5 laying hens.
Medium hens usually need 20-25 cm.

Heavy breeds need more room and lower, stable roosts. A communal nest is not counted like separate boxes. With a small flock it is safer to round up, not down.

For this flock, prepare at least

3nest boxes
Total roost length2.3 m
Example roost split2 × 1.15 m
Hens per nest box3.4
Floor area of 30 × 35 cm boxes0.32 m²

Do not place nests directly below the roost. Hens prefer a quiet, slightly darker nest, while roosts should be easy to reach and clean.

nest boxes = round up (hens ÷ hens per nest)

How to read the results without getting trapped by the numbers

The lower capacity is normally the important one. If the coop holds 30 hens but the run only suits 15, you do not have room for 30. Extra nest boxes also cannot fix a setup where quieter birds cannot reach feed or water.

  • Count only floor and ground the birds can really use.
  • Leave a margin for winter, rain, heat and temporary confinement.
  • After a week, compare the estimate with real feed and water use.
  • Increase allowances for large breeds, roosters and difficult ground.

Common questions about chicken coop calculations

How many chickens can be kept per square metre in a coop?

For a backyard flock, roughly 0.3-0.5 m² of usable indoor floor per average hen is a sensible planning range. Use more for heavy breeds and birds spending long periods indoors.

How much run space does one chicken need?

For a comfortable backyard run, 4 m² per hen is a useful starting point. Drainage, shade, cover and rotation can matter as much as the headline area.

How much feed does a laying hen eat per day?

Most adult laying hens eat about 100-120 g of complete feed a day. Breed, weight, weather, production and feed energy density all affect actual intake.

How much water does a chicken drink per day?

Around 0.3 l per adult hen is a reasonable mild-weather estimate. Demand rises sharply in heat, so water must remain continuously available.

How many nest boxes do 10 hens need?

At one nest for four hens, prepare three nest boxes. They may still choose one favourite, but extra boxes reduce queues and hidden eggs.

Assumptions and sources

These results are for planning a small backyard flock. They are not a building plan, veterinary advice or proof of compliance with a particular production system. Check local rules and observe your own birds.

Piotr Markot

Piotr Markot

Poultry keeper. Poultry keeper. I built these calculators to make everyday planning easier, but the final check is always the birds' condition, dry litter and what is really happening in the coop.

Finished calculating? Start recording the results.

Twoja Farma keeps flock records, egg collections, feed, costs and daily notes together in one place.

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