Hatch Rate Calculator
Turns eggs set and flock fertility into the number of chicks to expect — and works backwards from the number of chicks you want.
Figures reviewed against university extension guidance · Last reviewed August 2026
- Chicks to expect
- 10
- from the eggs you set
- Set this many instead
- 8 eggs
- to hit your target, rounded up
- Hatch rate
- 85%
- of all eggs set, not of fertile ones
- Fertile eggs
- 11
- what candling should show
Where the eggs go
- Hatch: 10
- Fertile but never hatch: 1
- Never fertile: 1
Swapped roosters? A hen stores viable sperm for up to 21 days, so eggs can still be the previous male's for that long.
Fertility and hatch rate are not the same number
These two get used interchangeably and they are not interchangeable. Fertility is the share of eggs that were fertilised at all — that is a rooster question. Hatch rate is the share that produce a live chick — that is an incubation question. Every egg has to clear both hurdles.
Mississippi State Extension gives the anchor: at 93% fertility, about 85% of eggs set hatch. Read those together and you get the third figure, the one nobody quotes: roughly 91% of the FERTILE eggs made it. So even a perfectly fertile egg is not a chick — about one in eleven fertile eggs still fails somewhere in the 21 days.
A worked example
Set a dozen eggs from a flock at the commercial reference fertility and you should expect 10 chicks — 11 of the twelve fertile, and 1 of those failing during incubation.
Now be realistic about a backyard flock. Drop fertility to 70% — an ordinary figure for a mixed-age flock with one hard-working rooster — and the same dozen eggs gives 8 chicks, a hatch rate of 64%. That is not a failure. It is what the arithmetic does when fertility slips, and it is why the number to fix is usually the rooster rather than the incubator.
Working the other way: to end up with 6 chicks at reference fertility you should set 8 eggs. The calculator always rounds up, because setting the exact expected number leaves you one bad egg short of the target and an under-filled incubator costs nothing.
Timing, and whose chicks you are actually hatching
A hen holds peak fertility for only about 3–4 days after a single mating, which is why a rooster running with the flock matters more than a rooster present in it. Below roughly 11 hens per male you get fertility at the cost of over-mated hens; above about 14, fertility is what suffers.
The figure worth remembering, though, is the other one: a hen's sperm storage glands keep sperm viable for up to 3 weeks. Swap or remove a rooster and eggs can still be the previous male's for 21 days afterwards. For a breeding project that is the difference between the cross you planned and the cross you got — wait the full three weeks before setting anything you care about the parentage of.
Sources
The fertility and hatchability anchor is Mississippi State Extension P3670: at 93% fertility, about 85% of eggs set hatch. Those are commercial broiler-breeder figures under controlled incubation — a backyard flock will usually do worse, which is why fertility is an input rather than a fixed number.
- Mississippi State University Extension (Tabler) — The Only Good Broiler Breeder Egg Is a Fertilized Egg (P3670)
- University of Georgia, Department of Poultry Science — Natural Mating and Fertilization
Frequently asked questions
- What is a good hatch rate for chicken eggs?
- Mississippi State Extension gives the commercial benchmark: at 93 percent fertility, about 85 percent of eggs set will hatch. That is a broiler-breeder flock under controlled incubation, so treat it as the ceiling rather than the expectation. Backyard hatches of 50 to 75 percent are common and not a sign anything went wrong.
- What is the difference between fertility and hatchability?
- Fertility is the share of eggs that were fertilised at all — a rooster question. Hatchability is the share that go on to produce a chick, which is an incubation question. They are often confused because "hatch rate" is quoted against both denominators. At the MSU reference point, 93 percent were fertile and 85 percent of all eggs set hatched, meaning about 91 percent of the FERTILE eggs made it. This calculator reports both so the number is never ambiguous.
- Why do fertile eggs fail to hatch?
- Most losses are incubation rather than fertilisation: temperature swings, humidity that stops the egg losing enough weight, insufficient turning, or a rough hatch at the end. Egg handling before setting matters too — eggs stored too long, too cold, or washed lose viability. Even a flawless setup loses some, which is why the calculator never predicts a 100 percent hatch even at 100 percent fertility.
- How many eggs should I set to get the chicks I want?
- Enter your target and the calculator works backwards, rounding up. At 93 percent fertility you need roughly 7 eggs for every 6 chicks; at 60 percent fertility that becomes about 11. Rounding up matters — setting the exact expected number leaves you one bad egg away from missing the target, and an incubator running slightly under capacity costs nothing.
- How long after adding a rooster are eggs fertile?
- A hen holds peak fertility for only about 3 to 4 days after a single mating, so fertility builds quickly once a rooster is running with the flock. Most keepers allow a week or two before collecting for the incubator, which gives the whole flock time to have been mated rather than just the hens near the top of the pecking order.
- If I swap roosters, whose chicks will I get?
- Possibly the old one's, for up to three weeks. A hen's sperm storage glands hold viable sperm for as long as 21 days, so eggs collected inside that window can still carry the previous male's genetics. If parentage matters — and for a breeding project it usually does — wait the full three weeks after a swap before setting anything.