How to Choose Eggs for Hatching: What Actually Decides Your Hatch Rate
Compiled and fact-checked from cited sources, reviewed by our editorial team. · Last updated:
There is an awkward truth at the heart of selecting hatching eggs: the one thing you cannot select for is the thing that matters most. You cannot tell from the outside whether an egg is fertile. Not by looking at the shell, not by candling it before incubation, not by floating it, not by shaking it. The first reliable answer comes when you candle on day 5 to 7 of incubation.
So everything you do at selection time serves a single purpose: protecting an embryo that may or may not be there. Don’t wash it, don’t chill it, don’t store it too long, and reject the eggs your incubator cannot handle.
Once you frame it that way, every rule below stops being a list to memorise and starts making sense.
Start with the flock, not the egg
Selection really begins before you pick up a single egg. However perfect the eggs look, a flock in the wrong condition gives you a poor hatch.
Is there a cockerel, and are there enough hens per cockerel? Fertility requires a male. In practice, one cockerel to eight or twelve hens is the working ratio. Too few males and fertility drops; too many and they spend their energy on each other, and fertility drops again.
Is the flock mature enough? Eggs from hens under 22 weeks are small and hatch measurably worse. Setting a pullet’s very first eggs is one of the most common beginner mistakes.
Is the flock healthy and properly fed? Calcium shortfall gives thin, fragile shells. Protein and vitamin shortfalls give weak embryos. Shell quality is a direct readout of the feed.
How often are eggs collected? At least twice a day. An egg left in the nest box gets dirty and sits warm, which starts uneven early development before you ever intend it to.
Weight and shape
An incubator is built for a certain range. Outside it, eggs either fail or produce compromised chicks.
Weight, for chicken eggs:
| Weight | Verdict |
|---|---|
| Under 50 g | Do not set — the chick will be very small |
| 50-57 g | Acceptable |
| 58-61 g | Ideal — best hatch rate and chick quality |
| 62-70 g | Usable, but hatchability starts to fall |
| Over 70 g | Reject — likely double-yolked |
Never set a double-yolked egg. Two embryos in one shell have neither the room nor the nutrients to finish; almost none hatch healthily. Unusually large, long eggs are frequently double-yolked.
Shape: normal oval only. Reject:
- Very round eggs (the air cell will not form in the right place)
- Very long, pointed eggs
- Symmetrical eggs where both ends look the same
- Anything with a distinct deformity, ridge or waist
The reason is mechanical as much as biological: an automatic turner cannot rotate these eggs correctly, and the embryo ends up wrongly positioned.
The shell
Through the whole incubation the shell is the embryo’s only protection, which is why this is where selection is strictest.
No cracks. Not even hairline ones. Hold each egg against a strong torch in a dark room: cracks appear as fine bright lines. This is the single most useful check available before setting.
Reject thin shells. An egg that glows unusually brightly and feels light for its size has a thin shell. In the humid warmth of an incubator it loses water too fast and lets bacteria in.
Reject rough, chalky or sandpapery shells. The pore structure is irregular, so water loss cannot be controlled.
Reject heavily soiled eggs. A little soil or a feather is fine. An egg smeared with droppings goes in the bin: an incubator is a perfect environment for bacteria, and one contaminated egg can explode and take the whole batch with it.
Never wash hatching eggs. The natural layer on the shell, the cuticle, keeps bacteria out. Washing removes it and draws water in through the pores — precisely the opposite of what you want. Rub light soiling off gently with dry fine sandpaper or a dry cloth. Do not use a damp cloth either. If an egg is genuinely dirty, let it go: rescuing one egg is not worth risking the batch.
Storage: where most hatches are lost
The time between collecting an egg and setting it affects hatch rate more than shape or weight ever will.
Duration: seven days maximum. For the first week hatch rates stay close to fresh. After day seven they fall a little each day, and most eggs stored beyond two weeks will not hatch at all. The cause is not the embryo dying but the vitamins degrading and the internal membranes losing their structure.
Temperature: 16-18 °C. This band matters. Warmer, and the embryo begins developing unevenly and exhausts itself before it reaches the incubator. Colder, and the cells are damaged.
Humidity: around 75 %. In dry air the egg loses water through its pores and the air cell grows faster than it should.
Position: pointed end down. The air cell sits in the blunt end; with the point down the air cell stays at the top and the yolk stays centred.
Turning: once a day. In a stored egg the yolk slowly settles towards the shell and can stick to the membrane. Propping one end of the carton on a book and swapping ends daily is enough — you do not need to turn eggs individually.
Hatching eggs never go in the refrigerator. A fridge runs at about 4 °C, and that temperature permanently damages the embryonic cells. An egg that has been refrigerated is, in practice, no longer a hatching egg. A cool pantry, a cellar or a corner of an air-conditioned room is the right place.
Shipped eggs
If you buy eggs from elsewhere, two things change.
Expect a lower hatch rate. Vibration in transit can detach or loosen the air cell and slacken the membranes. Around 50 % is considered normal for shipped eggs; do not judge them against the rate you get from your own flock.
Resting them is not optional. After unpacking, stand the eggs pointed end down at room temperature and leave them completely still for 12 to 24 hours. That lets the air cell settle back. Setting shipped eggs straight into the incubator measurably reduces the hatch.
Candle every egg as soon as you unpack. Transit cracks and loose or “rolling” air cells are found at this stage, and eggs with a detached air cell are usually best incubated upright and not turned.
Why supermarket eggs will not hatch
A question asked constantly, and the answer holds on three separate counts.
They are not fertile. Commercial egg production keeps no cockerels. No male, no fertilisation, no embryo to develop.
They have been washed or treated. The protective cuticle has been compromised.
They have been chilled. Somewhere in the supply chain they went cold, and that ends any prospect of development.
Labels like “organic” or “free-range” change none of this — they describe how the hen was housed, not whether a cockerel was present. Hatching eggs come from a flock that has a male, bought directly from a breeder or keeper.
Buying eggs to eat is a different exercise with different rules, covered in how to choose eggs.
The last check before setting
Minutes before the eggs go into the incubator, do three things:
- Candle them. Cracks, the position and stability of the air cell, and any dark patches or blood rings inside.
- Mark them. Write X on one side and O on the other. If you are turning by hand, this is how you keep track.
- Let them warm up. Do not take eggs from a cool store straight to 37.5 °C. Six to eight hours at room temperature prevents condensation on the shell and softens the thermal shock.
Frequently asked questions
How do I choose eggs for hatching? Take clean, uncracked, normally shaped eggs of 58-61 g from a flock that has a cockerel and is over 22 weeks old, and store them no more than seven days at 16-18 °C, pointed end down.
Can I tell if an egg is fertile before incubating? No. Not by candling, floating or shaking. Fertility only becomes visible when you candle on day 5 to 7 of incubation.
What weight should a hatching egg be? For chickens, at least 50 g, ideally 58-61 g. Over 70 g is usually double-yolked and should be rejected.
How long can hatching eggs be stored? Seven days at best. Hatchability falls each day after that, and most eggs older than two weeks will not hatch.
What temperature should they be stored at? 16-18 °C with about 75 % humidity. Refrigerator temperature kills the embryo.
Should hatching eggs be washed? No. Washing removes the protective cuticle and draws water through the pores. Rub light dirt off dry; discard heavily soiled eggs.
Can I incubate eggs that have been in the fridge? No. Around 4 °C permanently damages the embryonic cells.
Will supermarket eggs hatch? No. Commercial flocks have no cockerels, so the eggs are unfertilised, and they have also been washed and chilled.
Can I set a double-yolked egg? No. Two embryos cannot share the space and nutrients in one shell.
How many hens per cockerel? Eight to twelve in practice. Too few males lowers fertility; too many makes them fight and lowers it again.
Do stored eggs need turning? Yes, once a day. Raising alternate ends of the carton each day is sufficient.
What do I do with shipped eggs? Rest them pointed end down at room temperature, undisturbed, for 12 to 24 hours, then candle for cracks and air cell damage before setting.
Can I clean a dirty egg and use it? Light soil or a feather, yes, wiped dry. Droppings, no — one contaminated egg can spoil the whole batch.
Will small eggs hatch? They may, but the chicks are small and weaker. Below 50 g, do not set them.
Can I use a pullet’s first eggs? It is a poor bet. The flock should be at least 22 weeks old; younger birds lay small eggs with a low hatch rate.
Should I warm eggs before setting? Yes — six to eight hours at room temperature if they have come from a cool store. Going straight to 37.5 °C causes condensation and thermal shock.
Sources
- H&N International — Hatching egg management (weight range, flock age, shell and shape culling). https://hn-int.com/hatching-egg-management-2/
- Brinsea — Egg storage and handling (storage temperature, humidity, duration and turning). https://www.brinsea.com/t-eggstorage.aspx
- Hatchability.com — storage conditions for hatching eggs. https://www.hatchability.com/storage-conditions.html
- Incubator Warehouse — hatching egg selection criteria and shipped eggs. https://incubatorwarehouse.com/blogs/poultry-pals/how-to-select-quail-eggs-for-hatching