Ovatekly · Guides
Not hatching on day 21? Check these first.
Why a hatch runs late, how long the extension guides say to wait, what not to do while you wait, and how to find out afterwards what happened.
Short answer
Chicken eggs are due on day 21, and chicks should start to pip within about a day of that (Texas A&M AgriLife). Late hatches usually come from stored or large eggs, or from an incubator that ran slightly cool or too humid. Keep the lid shut, give them until the end of day 22, and candle or listen to an egg before you decide it will not hatch (Kansas State). Never help a chick out of the shell.
First
Are you counting the days the same way?
Count the day the eggs went in as day 0. Eggs set on a Saturday evening are due on the Saturday evening three weeks later, not the Friday.
Eggs taken from cool storage need 4 to 8 hours to warm to room temperature, and after they go in the reading dips for a while (Texas A&M). An evening setting of cold eggs starts the clock later than the calendar says.
Storage also adds time: each day in storage adds about one hour to incubation (Texas A&M), and eggs stored more than two weeks can run up to a day long (Texas A&M, 2000).
Sources: Texas A&M AgriLife Extension, Incubating and Hatching Eggs (POSC-PU-018, 2022); Texas A&M AgriLife Extension, Incubating and Hatching Eggs (B-6092, 2000).
The usual causes
Five reasons a hatch runs late
| Cause | What happens | Source |
|---|---|---|
| Stored eggs | About one extra hour per day of storage; Kansas State’s rule is 30 minutes for each day beyond 4. | Texas A&M; Kansas State |
| Large eggs or heavy breeds | Larger eggs in a batch hatch later than small ones, and heavy breeds later than White Leghorns. | Kansas State |
| Temperature a little low | Listed by Texas A&M as a cause of chicks hatching late. A thermometer that reads high makes a cool incubator look right. | Texas A&M, Table 3 |
| Humidity too high | Also a cause of late hatches, and of an air cell that is too small. | Texas A&M, Table 3 |
| Opening the lid | Lowers temperature and humidity, which delays hatching and may lower hatchability. | Kansas State |
Sources: Texas A&M AgriLife Extension, Incubating and Hatching Eggs (POSC-PU-018, 2022), Table 3; Kansas State University, Incubation and Reproduction (poultry Q&A).
Check the thermometer, not just the display. An independent thermometer at egg height, compared with the incubator’s reading, is the fastest way to tell a slow batch from a cool incubator. More in the temperature and humidity chart.
Patience, with a limit
How long to wait
Texas A&M’s guidance is short: chicks should start to pip within a day of the expected incubation period, and eggs not hatched one day after it can be discarded. For chickens, that means the end of day 22.
Kansas State adds two checks before you give up on an egg. Hold it to your ear: if you hear no movement, you can assume it will not hatch. Better still, candle it to see how far it got.
If nothing at all has pipped by day 22, the whole batch is late, which points to storage, egg size, or the incubator’s temperature or humidity rather than to individual eggs. Candle two or three eggs before deciding anything.
Sources: Texas A&M AgriLife Extension, Incubating and Hatching Eggs (POSC-PU-018, 2022); Kansas State University, Incubation and Reproduction (poultry Q&A).
While you wait
What not to do
- Do not help a chick out. Chicks that cannot hatch on their own usually die, and helped chicks that live usually do not thrive (Texas A&M); late-hatching chicks are usually weak or deformed (Kansas State).
- Do not keep opening the lid. Each opening drops temperature and humidity and delays the hatch further (Kansas State).
- Do not start turning again. Turning stops for the last three days (Texas A&M; Mississippi State).
- Do not chase the dial. Change the temperature only after you have checked it against a second thermometer.
Sources: Texas A&M AgriLife Extension, Incubating and Hatching Eggs (POSC-PU-018, 2022); Kansas State University, Incubation and Reproduction (poultry Q&A); Mississippi State University Extension, Important Incubation Factors.
Learn from the batch
Afterwards: find out what happened
Texas A&M suggests opening eggs that failed to hatch from the large end and classifying what you find: infertile (no development at all), early dead, middle dead, late dead, pipped but dead, or malpositioned. Each points to a different stage, and each has its own list of causes in Texas A&M’s Table 3, which is reproduced in the Hatch Guide’s troubleshooting table.
Write it down with the dates, the temperatures you saw and how long the eggs were stored. Texas A&M’s point is that records turn one bad hatch into an early warning for the next.
| What you find | Possible causes (Texas A&M, Table 3) |
|---|---|
| No development | Infertile egg, rough handling, temperature too high or too low, eggs stored too long or badly, breeder issues. |
| Blood ring, early dead | Old eggs, temperature too high or too low, power failure, eggs not turned, infection. |
| Dead after pipping | Eggs not turned in the first 2 weeks, thin shells, temperature or humidity too low or too high, infection. |
| Chicks hatched late | Large eggs, old eggs, temperature too low, humidity too high. |
Source: Texas A&M AgriLife Extension, Incubating and Hatching Eggs (POSC-PU-018, 2022), Tables 2 and 3.
If you hatched in an Ovatekly
Send us the log
Email contact@ovatekly.com with the day you set the eggs, a photo of the display and photos of any unhatched eggs. A person goes through it with you. If the incubator did not hold temperature, or the turner or a fan failed, the part or the unit is replaced under the 1-year limited warranty. If it was the set-up, we tell you exactly what to change for the next batch. We will not pretend a bad batch of eggs was the machine, and the warranty does not cover a failed hatch on its own, because fertility, egg handling and the room also decide it.
Questions
Questions people ask
How late can chicken eggs hatch?
Why are my chicken eggs not hatching on day 21?
Should I help a chick out of its shell?
Can I open the incubator to check on the eggs?
Some eggs hatched and some did not. What now?
Sources
Where the numbers come from
- Texas A&M AgriLife Extension, Incubating and Hatching Eggs (POSC-PU-018, 2022), text and Tables 2 and 3.
- Texas A&M AgriLife Extension, Incubating and Hatching Eggs (B-6092, 2000).
- Kansas State University, Incubation and Reproduction (poultry Q&A).
- Mississippi State University Extension, Important Incubation Factors.
Updated October 17, 2026. Written by the Ovatekly team. Temperatures, humidity levels and incubation periods on this page are general references from the extension publications named beside them, not Ovatekly specifications.
More from the hatch guides
A person for the whole hatch.
Every Ovatekly comes with Hatch Support: email a photo of your display or a candled egg to contact@ovatekly.com and a real person answers, from the day you set your eggs until they hatch.