How egg incubation works
An incubator does the job a broody hen does on the nest: it keeps fertile eggs warm, keeps the air moist and moves the eggs so the embryo grows evenly. Get those three things right and nature handles the rest. Get them wrong and you can lose a whole hatch without ever seeing what went wrong.
Temperature is the big one. Utah State University Extension puts it plainly: chicks can hatch "a day or two early if temperatures are a little high" and "a day or two late if temperatures are a little low," and "even a half of a degree makes a huge difference." That's why the calculator above gives a hatch window, not just a single date.
Humidity controls how much water the egg loses. Eggs are supposed to dry out a little as they develop. Mississippi State says an egg's weight "must decrease by 12% during incubation if good hatches are expected," and Texas A&M puts it at 12 to 14 percent for chicken eggs. Too little moisture loss and chicks come out soggy; too much and they can't break free of the membranes.
Turning is your job until lockdown, just as a hen shuffles her eggs on the nest. Turn at least three times a day, and make it an odd number of times so the eggs don't sit on the same side every night (University of Minnesota and University of Illinois Extension). Texas A&M recommends at least five turns a day, and Mississippi State four to six.
How the calculator counts days
We count the day you set the eggs as day 0. A chicken egg set on Saturday afternoon is due 21 days later, on a Saturday. Some keepers call the set day "day 1"; the hatch date is the same either way, but the milestone numbers shift by one, so stick with one system for your notes.
The day-by-day overview
Here's what a typical chicken hatch looks like. Ducks, turkeys, quail and the rest follow the same pattern on a different clock. Pick your bird in the calculator to see exact dates.
| Days | What's happening | What you do |
|---|---|---|
| 0 | Eggs go in | Set temperature and humidity, start turning |
| 1–6 | Embryo starts developing | Turn, check water, leave them be |
| 7 | Blood vessels are visible by candlelight | First candling; remove clear eggs |
| 8–13 | Rapid growth | Keep turning and topping up water |
| 14 | A chick can usually be seen by candlelight | Second candling |
| 15–17 | Final growth | Last days of turning |
| 18 | Lockdown | Stop turning, raise humidity, close the lid |
| 20–22 | Pips and hatching | Hands off; let them work |
For other birds, the calculator shifts every step: lockdown on day 25 for most ducks, turkeys and guinea fowl, day 15 for Coturnix quail and day 31 for Muscovy ducks, based on the Mississippi State incubation table and Texas A&M publication B-6092.
Candling: what to look for on day 7 and day 14
Candling means shining a bright light through the shell in a dark room to see what's inside. It's how you spot eggs that aren't developing before they spoil. Utah State notes that eggs which stop developing should come out, and University of Minnesota warns that such eggs "will rot quickly and may explode in the incubator." Nobody wants that cleanup.
Around day 7, a developing egg shows a network of veins. Utah State says "a healthy embryo will show veins extending and attaching to the eggshell by Day 7." Texas A&M describes the embryo as "a dark spot that becomes larger as incubation progresses."
- Clear egg: light passes straight through with no dark areas or vessels. It's infertile or never started. Remove it.
- Blood ring: a red ring or smear with no spidery veins means the embryo died early. Remove it.
- Veins and a dark spot: keep it in.
Around day 14, the chick fills most of the egg. Utah State says that by then "a chick can usually be seen," and Texas A&M says that eventually "only a dark mass and the air cell are seen." Remove any egg that shows little development; Minnesota advises removing eggs that "show little development at 10 days."
Sources differ on how late to candle. Virginia Tech's embryology tip sheet suggests candling on days 7, 14 and 18, while Utah State says "after 14 days, most eggs should not be candled to keep the developing chick at a constant temperature." If you do a final check at lockdown, be quick.
For birds other than chickens, extension sources don't publish separate candling days. Texas A&M suggests candling at about one-third of the incubation period, and that's the date the calculator shows. For a step-by-step walkthrough, read our guide on how to candle eggs.
Reading the air cell
The air cell at the big end of the egg is your humidity gauge. It should grow steadily as the egg loses water. University of Minnesota says its size "can be used to estimate whether the humidity should be increased or decreased," and Utah State sums it up: "To increase the air sack, decrease the humidity; to decrease the air sack, increase the humidity."
Lockdown explained
Lockdown is the last three days before hatch. It means three things:
- Stop turning. Utah State: "Three days before the expected hatch, stop turning the eggs." Texas A&M says not to turn "during the last 3 days to 4 days."
- Raise the humidity. Mississippi State says to go to "65 percent relative humidity or more" when hatching; Texas A&M's chicken tips say 65 to 70 percent. Utah State explains why: extra humidity "keeps the egg membrane pliable when the chick is hatching."
- Keep the lid closed. Mississippi State: "Keep the incubator closed during hatching to maintain proper temperature and humidity." Every time you open it, humidity drops fast and the membranes around a pipping chick can dry out.
If your incubator has an automatic turner, take the eggs out of it or switch it off on lockdown day. Our incubator lockdown guide covers setup, water trays and what to do if humidity crashes.
Temperature and humidity by species
All figures are for forced-air (fan) incubators unless noted. Wet-bulb readings are what a wet-bulb thermometer or hygrometer shows; many keepers just use a digital hygrometer and go by percent.
| Bird | Days to hatch | Stop turning | Forced-air temp | Wet bulb, incubation | Wet bulb, lockdown |
|---|---|---|---|---|---|
| Chicken | 21 | Day 18 | 99.5–100°F | 85–87°F | 90°F+ |
| Duck | 28 | Day 25 | 99.5–100°F | 85–86°F | 90°F+ |
| Muscovy duck | 35–37 | Day 31 | 99.5–100°F | 85–86°F | 90°F+ |
| Coturnix quail | 17 | Day 15 | 99.5–100°F | 85–86°F | 90°F+ |
| Turkey | 28 | Day 25 | 99–99.5°F | 84–86°F | 90°F+ |
| Goose | 28–34 | Day 25–27 | 99–99.5°F | 86–88°F | 90°F+ |
| Guinea fowl | 28 | Day 25 | 99.5–100°F | 85–87°F | 90°F+ |
Sources: Mississippi State's table gives 100°F for most birds and 99°F for turkeys and geese; Texas A&M B-6092 gives 99.5°F across the board and a hatcher wet bulb of 90–94°F. Where they differ, we show the range.
Still-air incubators have no fan, so warm air layers at the top. Measure "at the level where the embryos develop (at the top of the egg)," as Mississippi State puts it, with the thermometer bulb not touching the eggs. Mississippi State recommends 102°F; Virginia Tech's tip sheet gives 100.5 to 101.5°F.
In percent humidity, Mississippi State recommends 58 to 60 percent until lockdown, then 65 percent or more. For chicken eggs, other sources run a little drier: University of Minnesota says 50 to 55 percent and Texas A&M's tip sheet 55 to 60 percent. Waterfowl eggs need more humidity than chicken eggs, according to Minnesota.
Goose and Muscovy timing varies. Mississippi State lists 28 to 34 days for geese, Minnesota 29 to 31 and Texas A&M 30. For Muscovies, Mississippi State and Texas A&M say 35 to 37 days and Minnesota 33 to 35. The calculator uses day 30 for geese and day 35 for Muscovies and shows a wider hatch window for both.
Bantams don't get their own figures in any extension source we checked, so the calculator uses the 21-day chicken schedule for them.
Troubleshooting a hatch
Eggs are late (or nothing on day 21)
A slow hatch is usually a temperature story. Mississippi State: an incubator that "runs consistently cooler tends to produce late hatches," and Minnesota lists "temperature too low" as the cause of eggs not pipping until day 21 or later. Texas A&M adds large or old eggs and humidity that ran too high.
Before you give up:
- Check your thermometer against a second one. A reading that's off by a degree can explain a late hatch.
- Give it time. Texas A&M says chicks "should start to pip within a day of the incubation period listed for the species." Utah State says chicks that haven't hatched one or two days late likely won't survive. The calculator's "call it" date sits two days past the due date.
- Candle before you toss. Movement or a shadowed, dark egg means there's still a chick in there.
Our guide to eggs not hatching on day 21 walks through the full checklist.
Early hatches
The flip side: a warm incubator brings chicks out early. Mississippi State says one "that is too warm tends to produce early hatches," and Minnesota links early hatching with bloody navels to temperature that's too high.
Pipped but not hatching
A chick that has pipped still has a lot of work to do. Texas A&M says "the entire hatching process requires 10 hours to 20 hours" and not to worry "unless the process exceeds 20 hours." Its tip sheet notes chicks "may take nearly 24 hours to hatch."
It's hard to watch, but every source we checked says the same thing: don't help. Texas A&M: "Do not help chicks out of their shells. If they cannot hatch themselves, they likely will not survive." Virginia Tech and Utah State agree.
When many chicks pip and then stall, look back at your numbers. University of Minnesota links eggs that pip but don't hatch, chicks dead in the shell and sticky chicks to low humidity, low temperature or low humidity at hatching time.
"Shrink-wrapped" chicks
Keepers use "shrink-wrapped" for a chick stuck tight inside dried-out shell membranes. Extension publications don't use the term, but they describe the cause. Texas A&M warns that "the shell membranes should not dry to the chick during hatch," and that when humidity is too low the membranes "will be too tough to break." The fix is prevention: raise humidity at lockdown and keep the lid shut until the hatch is over.
Mushy or soggy chicks
Too much moisture causes the opposite problem. Texas A&M lists high humidity, wide temperature swings and poor ventilation behind "mushy or water-logged chicks." If your air cells stayed small all the way through, run a little drier next time.
Before your next hatch: egg storage
Good hatches start before the eggs go in. Mississippi State recommends storing hatching eggs at about 55°F and 75 percent humidity, "with the small end pointed downward," and setting them within 7 days. Texas A&M says hatchability "decreases rapidly" after 10 days of storage. Let cool eggs warm slowly to room temperature before setting them; Texas A&M suggests 4 to 8 hours.
Ready? Scroll back up, pick your bird and set date, and add the schedule to your calendar so lockdown day doesn't sneak up on you.
Last updated October 24, 2026. Figures checked against the university extension sources linked above. See our editorial policy.