Chicken Egg Incubation Chart: Day by Day, Day 1 to 21
A day-by-day chart of what develops inside the egg and what you do each day, from setting to hatch. Free printable PDF, with the source for every developmental stage.
Chicken eggs hatch on day 21. Turn them 3 to 5 times a day through day 18, candle on days 7, 14 and 18, then stop turning and raise humidity for lockdown on days 19 to 21. Inside the egg, the heart beats by 42 hours, feathers start at day 8, the beak turns toward the air cell at day 17, and the chick pierces the air cell and starts breathing air at day 20.
Set a different date or species and get your own dates with the incubation calendar calculator.
The 21-day chart
Temperature stays at 99.5°F (37.5°C) in a forced-air incubator, or 101.5°F still-air, for all 21 days. Humidity is 50–55% through day 18, then 65–75% for lockdown. Neither changes day to day, so neither is repeated in the chart below — see incubator temperature and humidity for the full treatment.
| Day | What’s developing inside | What you do |
|---|---|---|
| 1 | First resemblance to an embryo (16 h). Alimentary tract (18 h), vertebral column (20 h), nervous system (21 h), head (22 h), eye (24 h). | Turn 3–5× |
| 2 | Heart begins (25 h). Ear begins (35 h). Heart beats (42 h). | Turn 3–5× |
| 3 | Nose (60 h), legs (62 h), wings (64 h). | Turn 3–5× |
| 4 | Tongue begins. | Turn 3–5× |
| 5 | Reproductive organs form and sex differentiates. | Turn 3–5× |
| 6 | Beak begins. | Turn 3–5× |
| 7 | — | Turn 3–5× · Candle |
| 8 | Feathers begin. | Turn 3–5× |
| 9 | — | Turn 3–5× |
| 10 | Beak begins to harden. | Turn 3–5× |
| 11 | — | Turn 3–5× |
| 12 | — | Turn 3–5× |
| 13 | Scales and claws appear. | Turn 3–5× |
| 14 | Embryo moves into position for breaking the shell. | Turn 3–5× · Candle |
| 15 | — | Turn 3–5× |
| 16 | Scales, claws and beak becoming firm and horny. | Turn 3–5× |
| 17 | Beak turns toward the air cell. | Turn 3–5× |
| 18 | — | Final candle, then stop turning |
| 19 | Yolk sac begins to enter the body cavity. | Lockdown — no turning, no opening |
| 20 | Yolk sac completely drawn into the body cavity. Embryo fills the egg except the air cell; the chick pierces the air cell and starts breathing air. | Lockdown — no turning, no opening |
| 21 | Hatch. | Leave the lid shut |
Download the chart as a printable PDF — one page, sized for a letter sheet, with a tick box for each day.
Why some days are blank
Days 7, 9, 11, 12, 15 and 18 have a dash rather than a milestone, and that is deliberate.
The day-by-day list everyone reproduces traces back to a single source: A. L. Romanoff, Cornell University Extension Bulletin 205, still carried by Mississippi State Extension today. Romanoff assigned milestones to fifteen of the twenty-one days. The other six are not blank because nothing happens — growth is continuous — but because the published list does not name a distinguishing event for them.
Most charts online quietly invent something to fill those rows. Once you notice that, you can spot which charts are copied from a source and which are copied from each other. This one leaves them empty and tells you why.
The blank days are not empty for you, though. Day 7 and day 18 are two of the three candling days, so those rows carry the most important instructions on the chart.
The three things you actually do
Everything in the right-hand column reduces to three jobs.
Turn the eggs, 3 to 5 times a day, through day 18. Turning stops the developing embryo settling against the shell membrane and sticking to it. Texas A&M’s classroom guide asks for three to five turns daily for the first 18 days. Use an odd number so the eggs do not spend every night on the same side. If you have an automatic turner this happens for you; mark an X on one side and an O on the other if you are turning by hand, so you can see at a glance which eggs you have already done.
Candle on days 7, 14 and 18. Candling is shining a bright light through the shell to see what is inside. It tells you which eggs are developing, which were never fertile, and — from the size of the air cell — whether your humidity is right.
Lock down on day 18. Stop turning, raise humidity to 65–75%, and stop opening the incubator. All three matter, and the third is the one people break.
What you see when you candle
| Day | What a developing egg looks like | What to remove |
|---|---|---|
| 7 | A dark spot with fine blood vessels radiating outward, like a spider. | Clear eggs (infertile). A blood ring — a red circle with no embryo — means it died in the first few days. |
| 14 | Most of the egg is dark. The air cell at the blunt end is clearly larger. You may see movement if you watch for 30 seconds. | Eggs that have gone clear or show a loose dark mass with no vessels. |
| 18 | A solid dark mass. The air cell takes up roughly a third of the egg. | Last chance to pull an egg that never developed. |
An LED flashlight in a dark room works as well as a purpose-made candler. What you are looking for on each of the three candling days is covered in candling chicken eggs day by day. White eggs are far easier to read than brown ones, and very dark shells — Marans, Welsummer — may be impossible to candle reliably at all. If you cannot tell, leave the egg in. A doubtful egg costs you nothing; a wrongly discarded one costs you a chick.
The air cell is the part worth paying attention to. It grows as moisture leaves the egg, and by day 18 it should be about a third of the egg. Noticeably smaller means your humidity has been too high, and the chick may not have room to pip.
Days 19 to 21
Lockdown is the last three days, and the instruction is mostly stop doing things.
By day 19 the yolk sac is drawing into the body cavity — the chick is absorbing its own packed lunch, which is what will feed it for the first day or two after hatch. That is why a newly hatched chick does not need food immediately.
By day 20 the chick fills the egg except for the air cell, punches through into it, and starts breathing air for the first time. This is the internal pip. You may hear peeping from inside an egg that still looks untouched. Then comes the external pip, a crack in the shell, and finally the chick cutting a rough circle around the blunt end and pushing out.
The whole process takes the better part of a day. A chick that pipped this morning and has not progressed by this evening is usually normal, not stuck. Texas A&M’s guidance is not to worry about how long an individual chick takes unless it exceeds 24 hours.
Every time you lift the lid, humidity drops for five to ten minutes. A chick that has already pipped is sitting with its membrane exposed to that air, and drying it out shrink-wraps the chick into a shell it had already broken. You will hear peeping and want to look. Do not.
Hatching with a class or with kids
This chart is built to be printed and put on a wall, because that is how most people use a 21-day countdown.
A few things worth knowing if you are running this with children:
- Set eggs on a Tuesday or Wednesday. Texas A&M recommends this specifically so that day 21 lands on a school day rather than a Saturday.
- Supermarket eggs will not hatch. They are not fertile. This is the single most common way a classroom hatch fails before it starts.
- Expect around 80% fertility, and fewer than that hatching. Setting a dozen and getting eight chicks is a normal, successful hatch. Framing that up front turns a disappointment into a data point.
- The blank days are a teaching opportunity. Day 9 and day 12 are chances to ask what the chart does not tell us and why — which is a more honest science lesson than a row invented to fill the gap.
When the hatch runs early or late
The calendar itself is diagnostic. Texas A&M’s troubleshooting table maps the common outcomes back to causes:
| What happened | Likely cause |
|---|---|
| Chicks hatch early | Incubator running warm |
| Chicks hatch late | Incubator running cool, or eggs were old or large |
| Air cell too small at day 18 | Humidity too high, days 1–19 |
| Air cell too large; chick small and dehydrated | Humidity too low, days 1–19 |
| Blood ring at first candling | Old eggs, or temperature too high or too low early on |
| No development at all | Infertile eggs, or rough handling before setting |
A hatch that comes off on day 19 or day 23 is telling you to check your thermometer before your next set, not that your eggs were unusual.
Frequently asked questions
How long do chicken eggs take to hatch?
21 days from the day they are set. Bantams sometimes hatch on day 20 and heavy breeds occasionally take 22. Other species differ substantially — quail at 17 days, ducks at 28.
What day do you stop turning chicken eggs?
After day 18. The last three days are lockdown, when the chick is positioning to hatch and turning would disorient it.
What days should I candle chicken eggs?
Days 7, 14 and 18. Day 7 shows you which eggs are fertile, day 14 confirms continued development, and day 18 is the last look before lockdown.
What is happening on day 20?
The yolk sac finishes drawing into the body cavity, the chick fills the egg except for the air cell, and it pierces the air cell to breathe air for the first time. Peeping from an unbroken egg on day 20 is normal.
Why does my chart have blank days?
Because the published source — Romanoff’s Cornell bulletin, still carried by Mississippi State Extension — does not assign a milestone to every day. Growth is continuous; the list simply names fifteen distinguishing events across the 21 days. Charts that fill in all 21 are adding detail their source does not support.
Can I open the incubator during hatching?
No. Humidity drops for five to ten minutes each time, and a chick that has already pipped can shrink-wrap into its shell. This is the most common cause of a chick that dies after breaking through.
How many eggs should I expect to hatch?
Around 80% of eggs are fertile, and not all fertile eggs hatch. Eight chicks from a dozen eggs is a normal result for a backyard or classroom incubator.
Sources
- Mississippi State University Extension — Stages in chick embryo development and The Avian Embryo (PDF): every developmental milestone in the chart above, including the hour-level detail for days 1 to 3. MSU credits the list to A. L. Romanoff, Cornell University Extension Bulletin 205, which is the original source of the day-by-day sequence reproduced across the web.
- Texas A&M AgriLife Extension — E-635, Hatching Eggs in the Classroom (PDF): 99.5°F set temperature, turning 3 to 5 times daily for the first 18 days and not at all for the last 3, the day-20 air cell and start of pulmonary respiration, the 24-hour hatching window, the ~80% fertility expectation, the Tuesday/Wednesday setting advice, and the hatching-problems table.
- Mississippi State University Extension — poultry incubation guide (PDF): the 1°F tolerance and its early/late hatch consequences, and the wet-bulb humidity figures.
Days with a dash carry no milestone in the published list, and are left empty rather than filled with invented detail. The candling schedule (days 7, 14, 18) matches the incubation calendar; the early-stage humidity figure of 50–55% sits at the dry end of a published range of roughly 50–60%, explained in incubator temperature and humidity.
Figures are planning guidance for backyard and classroom incubation, not veterinary advice. Last reviewed August 2026.