Fertile eggs should be positioned with the pointed end down and the blunt (large) end up, both during storage and when setting them in the incubator. This orientation keeps the air cell at the top of the egg, which the developing chick needs to take its first breath before hatching. Getting this wrong can be fatal to the embryo.
Why the Blunt End Must Face Up
Every egg has a small pocket of air called the air cell, located at the blunt end between the outer shell membrane and the inner egg membrane. This air cell grows larger as incubation progresses, and it serves a critical purpose in the final days before hatch. Around day 18 of a 21-day chicken incubation, the embryo rotates so its head tucks under its right wing with the beak pointing upward toward the blunt end. The chick then pushes through the internal membrane into the air cell and inflates its lungs for the first time. This moment is called an internal pip, and it’s the chick’s transition from absorbing oxygen through the shell to actually breathing air.
If an egg is set with the pointed end up, the chick’s head ends up at the opposite end from the air cell. Internal pipping becomes impossible, and the embryo typically dies. This single positioning mistake is one of the most preventable causes of late-term embryo death in incubation.
Positioning During Storage
Proper orientation starts before the incubator is even turned on. Store fertile eggs in egg cartons with the big end up. This keeps the yolk centered and the air cell intact at the blunt end. Eggs stored on their sides or pointed-end-up can develop displaced air cells, which compromises the embryo’s ability to orient correctly later in development. Most breeders store eggs for up to seven days before setting, and maintaining the correct position throughout that period gives the embryo the best starting conditions.
Vertical vs. Horizontal in the Incubator
Most commercial and hobbyist incubators hold eggs in one of two ways: upright in trays (pointed end down, tilted at an angle) or flat on their sides. Both can produce successful hatches, but they work differently.
Tray-style incubators hold eggs at roughly a 45-degree angle from vertical and use an automatic mechanism to tilt them side to side. This is the standard setup in commercial hatcheries and most home incubators with auto-turning features. The key rule is the same: pointed end down, blunt end up.
A broody hen, by contrast, keeps her eggs horizontal. She nestles them on their sides and uses her beak and body to roll them throughout the day. If you’re hand-turning eggs in a still-air incubator without trays, laying them on their sides and turning by hand mimics what a hen does naturally. Mark one side of each egg with an “X” and the other with an “O” so you can track which way you’ve turned them.
How Often and How Far to Turn
Turning prevents the embryo from sticking to the inner shell membrane, and it helps the developing chick absorb nutrients from the egg white and yolk. Without regular turning, especially in the first two weeks, embryos develop poorly or die.
Commercial incubators typically turn eggs 24 times per day at a 45-degree angle, and research in poultry science has found this frequency produces high hatchability rates. The theoretical optimum is actually 96 turns per day, but the improvement over 24 turns is small enough that most machines don’t bother. Reducing turns to just 3 per day significantly lowers hatch rates.
If you’re turning by hand, aim for a minimum of five to seven times per day. Use an odd number of turns so the egg spends alternating nights on opposite sides. Turning three times daily is better than not turning at all, but five or more times gives noticeably better results. Each turn should rotate the egg roughly 180 degrees if the eggs are on their sides, or tilt them 45 degrees in each direction if they’re upright in trays.
When to Stop Turning: Lockdown at Day 18
On day 18 of chicken egg incubation (day 16 or 17 for bantam breeds), you enter what’s called “lockdown.” This means all turning stops, and the incubator stays closed until the chicks hatch around day 21.
If your eggs have been upright in trays, lay them gently on their sides at this point. The chick needs to rotate freely inside the egg to get into hatching position, with its head tucked under its right wing and its beak aimed at the air cell. Continuing to turn eggs or leaving them upright during lockdown can prevent the chick from completing this rotation. Once you’ve laid the eggs down and closed the incubator, resist the urge to open it. The humidity and temperature stability during these final three days directly affects whether chicks can pip through the shell without the membrane drying out and trapping them.
What Happens When Positioning Goes Wrong
Incorrect egg orientation leads to embryo malpositions, where the chick develops in an abnormal alignment inside the egg. The most dangerous of these is “head in small end,” where the chick’s head is pointed toward the narrow end of the egg and away from the air cell. These embryos almost never hatch.
Another common malposition is “head under left wing” instead of the correct right wing. This affects anywhere from 1 to 20 percent of embryos that survive to day 18, and it’s usually lethal. Affected embryos tend to be smaller and often have developmental abnormalities. Their beaks end up turned away from the air cell, making pipping unlikely. While genetics and other factors play a role in malpositions, correct egg orientation and consistent turning throughout incubation reduce the risk substantially.
Quick Reference by Incubation Stage
- Storage (before incubation): Blunt end up in egg cartons, stored at 50 to 60°F for up to 7 days.
- Days 1 through 17: Pointed end down in trays (tilted 45 degrees each way) or on their sides if hand-turning. Turn at least 5 times daily, ideally more.
- Day 18 through hatch (lockdown): Lay eggs on their sides. Stop all turning. Keep the incubator closed.
The positioning principles are the same whether you’re hatching chicken, duck, quail, or turkey eggs. The only differences are the total incubation length and the specific day lockdown begins, which varies by species. For all of them, the rule that matters most is simple: air cell up, pointed end down, and consistent turning until lockdown.