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Chicken eggs hatch in 21 days at 99.5°F (37.5°C). The heart beats from day 2, candling shows an eye spot and veins on day 7, and the egg is mostly dark by day 14. Turn 3–5 times a day at 40–50% humidity until day 18, then stop turning and raise humidity to 65–70% (lockdown). Chicks pip on days 19–20 and hatch on day 21.
Chicken incubation at a glance: week by week
The 21 days split neatly into three weeks. Temperature never changes. Humidity and turning change once, at day 18. Count the day you set the eggs as day 0, so day 1 begins 24 hours later.
| Week | Days | Temperature | Humidity | Turning | Your main job |
|---|---|---|---|---|---|
| Week 1 | 0–7 | 99.5°F | 40–50% | 3–5× a day | Keep the lid shut; candle on day 7 |
| Week 2 | 8–14 | 99.5°F | 40–50% | 3–5× a day | Check air cell growth; candle on day 14 |
| Week 3 | 15–21 | 99.5°F | 40–50%, then 65–70% from day 18 | Stop on day 18 | Lockdown on day 18; hands off until hatch |
Want real dates instead of day numbers? Put your set date into the hatch date calculator and it will give you candling, lockdown and hatch dates.
Week 1 (days 0–7): heart, eyes and blood vessels
The first week is the busiest for the embryo and the quietest for you. Nearly every organ starts forming, so steady temperature matters more now than at any other time. Open the incubator only to turn eggs if you turn by hand.
- Day0
Set the eggs
Warm the eggs to room temperature for 6–8 hours first, then set them in an incubator that has already held 99.5°F for at least 24 hours. Expect the temperature to dip for a few hours while the eggs warm up. Don’t chase it with the thermostat.
Write down the set date and time - Day1
Head, eyes and spine begin
Within the first 24 hours the head, the eyes and the vertebral column start to form. Nothing is visible yet when candling.
Check temperature twice - Day2
The heart starts beating
Blood vessels form across the yolk and the tiny heart begins to beat. Ears start forming. Turning becomes important from now on so the embryo does not stick to the shell membrane.
Start turning 3–5× a day - Day3
Membranes and limb buds
The extra-embryonic membranes that will carry oxygen and nutrients start to form, along with the first buds of the wings and legs.
Turn; keep humidity 40–50% - Day4
Eye pigment appears
The eye begins to darken, and the tongue starts to form. On white or pale eggs you may now see a small dark dot with thin veins around it, like a spider. Brown eggs usually need a few more days.
Optional early candle (white shells) - Day5
Reproductive organs form
The embryo’s sex organs begin to develop. The vein network keeps spreading outward over the yolk.
Turn; don’t open the lid for long - Day6
The beak begins to form
The beak starts to take shape and the embryo begins to make small movements. The veins should now reach well out toward the shell.
Turn; get your candler ready - Day7
First candling day
The egg tooth is distinct and the wing and leg segments are visible. When candled, a fertile egg shows a dark eye spot with spider-like veins. A clear egg is infertile or died very early; a sharp red ring is a blood ring (early death). See the candling guide for pictures.
Candle tonight; remove clears and blood rings
Week 2 (days 8–14): feathers, claws and a growing air cell
In week two the embryo grows fast and starts to look like a bird. Your job is routine: turn, keep the water topped up, and watch that the air cell at the blunt end is slowly getting bigger.
- Day8
Feather tracts appear
The rows where feathers will grow become more distinct along the back. The embryo is now large enough to see moving when you candle.
Turn; top up water if needed - Day9
Toes form
The toes are formed and the first feather follicles are developing. The dark area on candling covers more of the egg each day.
Turn - Day10
The beak hardens
The beak begins to harden and feather follicles cover much of the body. Candled, the egg shows a larger dark mass with thick veins running to the edges.
Optional: weigh a sample of eggs - Day11
Rapid growth
The embryo keeps gaining size and moving, and its feather follicles spread over the wings and legs. The albumen (egg white) is steadily being used up.
Turn - Day12
Down and scales
Down is present on the body, the eyes are nearly closed, and scales appear on the legs.
Turn - Day13
Claws appear
Claws form on the toes and the scales on the legs become more defined. The embryo now fills most of the shell.
Turn; check thermometer against a second one - Day14
Second candling day
The eyes are closed and the embryo starts turning so its head points toward the air cell. A healthy egg looks mostly dark with a clear, defined air cell at the blunt end. Eggs that were alive on day 7 but now show a fuzzy, uneven outline and no movement are often quitters.
Candle; note air cell size
Week 3 (days 15–21): lockdown, pipping and hatch
The chick spends its last week growing, absorbing the yolk and getting into hatching position. Day 18 is the only date in the whole hatch where you have to change settings.
- Day15
Down covers the body
Down now covers most of the body and the intestines begin to move inside the abdomen.
Turn; buy or check brooder supplies - Day16
Albumen nearly gone
The chick has used up almost all the egg white and now relies on the yolk for food. Beak, claws and scales are firm.
Turn; set up the brooder - Day17
Head under the right wing
The head tucks under the right wing as the chick starts moving into hatching position. Amniotic fluid decreases.
Optional quick candle before lockdown - Day18
Lockdown
Growth is nearly complete. Stop turning, take out the turner or switch it off, lay the eggs flat, raise humidity to 65–70%, and close the lid. On candling the egg is dark with a large air cell whose lower edge may tilt or dip.
Stop turning; humidity to 65–70%; lid shut - Day19
Yolk enters the body; internal pip begins
The yolk sac starts to be drawn into the abdomen. The chick points its beak into the air cell and breaks through the inner membrane (internal pip) to breathe air for the first time. You may hear faint peeping.
Lid stays shut - Day20
External pip
The yolk is fully absorbed and the chick breathes from the air cell. Many chicks crack a small hole in the shell (external pip) on day 20 or early day 21, then rest for hours.
Watch, don’t help - Day21
Hatch day
The chick “zips” around the shell and pushes free. From first external pip to hatch usually takes 12–24 hours. Leave chicks inside until they are dry and fluffy, up to 24 hours.
Move dry chicks to a 95°F brooder
Don’t help a chick out on day 20 or 21. Long pauses after pipping are normal while blood vessels in the membrane shrink. Pulling shell off too early can cause bleeding. If there’s no progress at all 24 hours after external pip, read when and how to assist.
What day should you candle chicken eggs?
Candle chicken eggs on day 7 and day 14. Day 7 is when fertile eggs clearly show an eye spot and veins, even through most brown shells. Day 14 lets you catch embryos that died in week two before they spoil.
- Day 4–5: possible with white or very pale shells, but early signs are easy to misread. If unsure, leave the egg in.
- Day 7: remove clear eggs and blood rings.
- Day 14: remove eggs that have stopped developing. A live egg is mostly dark.
- Day 17 or 18: optional last check before lockdown so a dead egg doesn’t sit in the hatcher for three days.
Keep each egg out of the incubator for only a few seconds. A cooled egg recovers quickly; a dropped one does not.
Day 18 lockdown checklist
Lockdown on day 18 means you stop turning, raise humidity to 65–70%, and leave the lid closed until hatching is over. The chick needs to stay in position to pip, and the higher humidity keeps the shell membranes from drying out.
- Candle quickly and remove any eggs that have clearly stopped developing.
- Take out the automatic turner or switch it off. Lay eggs on their sides.
- Put non-slip shelf liner or paper towel on the floor so chicks get grip.
- Fill the water channels to raise humidity to 65–70%. A wet sponge helps in small incubators.
- Check the temperature is still 99.5°F after the lid is closed.
- Close the lid and don’t open it until the hatch is done or 24 hours after the last chick.
Getting humidity right before day 18 matters just as much. If you aren’t sure your eggs are losing enough moisture, the incubator humidity guide shows how to check with a kitchen scale or by air cell size.
Hatching early or late: what the timing tells you
A hatch starting on day 19 or 20 usually means the incubator ran a little hot. A hatch that drags into day 22 or 23 usually means it ran cool, or the eggs were stored a long time before setting. Bantam eggs are often a day early because they are small.
If nothing has hatched by day 21, keep the lid shut and give the eggs until day 23 before deciding anything. Then candle the remaining eggs before throwing any away: an egg with movement or a dipped air cell is still alive. For what went wrong in a poor hatch, see why eggs don’t hatch, and for the full method from setup to brooder, see how to hatch eggs in an incubator.
Frequently asked questions
What does a chicken egg look like on day 7?
Held over a candler on day 7, a fertile chicken egg shows a dark spot (the eye) in the middle of a network of red, spider-like veins, and the embryo may move. An infertile egg glows evenly with only a faint yolk shadow. A sharp red ring with no veins is a blood ring, meaning the embryo died early.
When does a chick embryo’s heart start beating?
On about day 2 of incubation. Blood vessels form on the yolk at the same time. You can’t see the heartbeat by candling that early, but by day 4–5 the vein network is visible in white eggs and by day 7 in most brown eggs.
Why is day 18 called lockdown?
Because the incubator gets “locked” closed. On day 18 you stop turning chicken eggs, raise humidity to 65–70%, and keep the lid shut until the hatch is finished. Opening it lets humidity escape fast, which can dry the membrane around a pipped chick and trap it.
Can I still turn eggs on day 19?
No. By day 19 the chick is moving its beak into the air cell to pip. Turning can push it out of position. If you forgot to stop the turner on day 18, switch it off as soon as you notice and lay the eggs flat. One late day rarely ruins a hatch.
How long after pipping does a chick hatch?
Most chicks hatch 12–24 hours after the first external pip, the small crack in the shell. Internal pip, when the beak breaks into the air cell, happens a day or so earlier. Long rests between pecking are normal, so don’t assist unless there’s been no progress for 24 hours.
What should I do if my chicken eggs haven’t hatched on day 21?
Wait. Keep the lid closed and the humidity up until day 23, because a cool-running incubator often delays the hatch by one or two days. Then candle each remaining egg: movement, veins or a dipped air cell mean it’s alive. Only discard eggs that are clearly dead or smell bad.