How many hens do I need for a dozen eggs a day?

It depends on the lay rate, which is the share of hens laying on any given day. At a lay rate of 80 percent you need 15 hens for 12 eggs a day, and at 60 percent you need 20. Lay rate is not a constant: it falls with age, drops sharply through a moult, and responds to day length, so a flock sized on a peak figure will come up short for part of the year.

Why does egg production drop in winter?

Mostly day length, which is what triggers laying, and moult, which is when a hen replaces her feathers and stops laying for several weeks. Both land in the same part of the year, so the seasonal dip is deeper than either alone would make it. Sizing a flock on the annual average rather than the peak, or accepting a shortfall for part of the year, are the two honest options.

What does it cost to produce a dozen eggs?

Feed is the largest cost and bird replacement is the one most often forgotten. A hen eats whether she is laying or not, so a low lay rate raises the feed cost of every egg produced, and the pullet has to be bought or reared before she lays anything. Counting both gives a cost per dozen that can be compared with a supermarket price, which is usually the comparison people actually want.

Egg Production Flock Size Calculator NZ

How many hens you need depends almost entirely on the lay rate, which is the share of the flock laying on any given day, and the mistake worth avoiding is treating that rate as a constant. It falls as birds age, it drops away sharply through a moult when hens replace their feathers and stop laying for several weeks, and it responds to day length. Those last two land in the same part of the year, which is why the winter dip is deeper than either would produce on its own, and why a flock sized on a peak rate will be short for months. This works out the birds needed at whatever rate you enter, then does the same at a lower rate so the seasonal gap is visible rather than discovered. It also prices the eggs. Feed is the largest cost and the one that behaves counterintuitively: a hen eats whether she is laying or not, so a lower lay rate raises the feed cost of every egg she does produce rather than lowering the bill. Bird replacement is the cost most often left out entirely, since a pullet has to be bought or reared before she lays anything at all. Counting both gives a cost per dozen you can hold against a supermarket price.

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Eggs wanted a week

Lay rate

Winter lay rate, for the comparison

Feed a bird a day

Feed price

/kg

Cost of a replacement pullet

Weeks a hen is kept laying

hens needed at the lay rate entered

Hens at the winter rate39

Feed a week19.3 kg ($25.99)

Cost a dozen$3.46

Of that, feed$2.60

Holding production through the winter dip would take 17 more hens, or 39 in total. A hen eats whether she is laying or not, so a lower lay rate raises the feed cost of every egg rather than lowering the feed bill.

No lay rate, feed intake or bird cost is supplied here. Lay rate depends on the breed, the age of the flock, the season and the management; feed intake depends on the bird and the ration. Take all of them from your own flock or from the breed information for the birds you have.

How it works

Eggs a week divided by seven gives eggs a day, and dividing that by the lay rate gives the hens needed, rounded up because you cannot keep part of a hen. The same calculation at the winter rate shows what the flock would have to be to hold production through the dip. Feed is the bird count multiplied by the daily intake, and the cost a dozen adds the feed cost to the bird replacement cost, spread across the eggs a hen lays in her laying life, then scaled to twelve.

Two ways to handle the seasonal dip

Either size the flock for winter and carry surplus birds and surplus eggs for the rest of the year, or size it for the good months and accept being short in winter. Both are legitimate and the arithmetic here makes the choice explicit rather than leaving it to be discovered in June. Staggering the flock so birds are of different ages is the third approach, which smooths the moult out rather than having the whole shed stop at once, and it is the one commercial operations use.

Worked example

Wanting 120 eggs a week is about 17.1 eggs a day. At an 80 percent lay rate that needs 22 hens, and at a winter rate of 45 percent it would need 39, which is the size of the seasonal problem in one number. Twenty two hens eating 125 grams a day get through 19.3 kilograms of feed a week, costing $25.99. Over a 70 week laying life a hen at 80 percent lays 392 eggs, so a $28 pullet adds about 7 cents an egg. Together the eggs cost $3.46 a dozen, of which $2.60 is feed.

Related calculators

Egg Incubation: hatching your own replacements.
Pig and Goat Feed Cost: the same arithmetic for other stock.
Lifestyle Block Stocking: what else the block carries.
Feed Conversion Ratio: feed into product, generally.

Data sources: no lay rate, feed intake or bird cost is supplied, because all three depend on the breed, the age of the flock, the season and the ration. Every figure is one you enter.