Short answer: Weigh each hatching egg on a scale that reads to 0.1 gram, then set only the eggs that sit close to the tray median. Eggs within about 5 percent of that median hatch into a more even batch, and the weight tells you how much water each egg should lose in the machine. Check shape second, because a misshapen egg often weighs wrongly for its length.
Key takeaways
- Weigh every egg on a scale that reads to 0.1 gram, and check the scale against a known weight before each sort.
- Set the eggs within about 5 percent of the tray median, and keep edge eggs in their own labelled tray.
- Aim for a loss of about 12 to 13 percent by lockdown, and weigh five or six marked eggs to check it.
- Judge shape after weight, and reject eggs that are very round, very pointed, cracked or sandy.
- Write the median, spread and source on every tray so a poor hatch can be traced to its cause.
Weight sorts the eggs. It does not vouch for them
Most growers ask whether an egg is fertile before they ask how alike the eggs are. The second question matters more at the setting table. A machine treats every egg in the tray the same, so a mixed tray gives you a mixed hatch: some chicks dry and walking while others are still a day from pipping, and a tail of runts at the end that nobody wanted to pay for.
Weight is the cheapest sorting tool you own. It will not tell you whether an egg was fertilised, and a heavy egg can be dead from the start. What it does tell you is how much egg you are asking the embryo to work with, and roughly how much water that egg must lose before the chick is ready to pip. Those two numbers are what make one set of eggs behave like another.
At our hatchery in Kasoa we treat weight as a question of uniformity. We are not hunting for the biggest egg in the tray. We are looking for the eggs that belong together. If you want to know who is doing the sorting, our story is on the about page.
A scale that tells the truth, and how to check it
A kitchen scale that rounds to whole grams is not good enough. The difference between a 61 gram egg and a 60 gram egg is a real difference across a tray, and a whole-gram scale hides the drift that matters. Buy a digital scale that reads to 0.1 gram with a capacity of at least 200 grams, and keep it on a flat table away from draughts and the fan.
Check it before every sort with a known weight. A 50 gram calibration weight is ideal. If you have nothing so exact, a sealed bottle of water weighed on a reliable scale elsewhere will do for a rough check. If the reading wanders by more than a tenth of a gram, switch off, wait a minute and check again. Battery scales lie quietly as the battery weakens, and that is how a whole tray lands in the wrong band without anyone noticing.
Weigh every egg on its own, write the number on a tray map, and never trust your memory of the last tray you sorted.
Bands built from your own tray, not from a chart alone
Breeder companies publish a target weight range for the eggs their parent flock should lay, and it is worth reading that guide. Our breed profiles are a starting point for the same question. But the band that matters on your farm is the one your own tray defines. Flock age, feed, season and the temperature in the house all move the average. A fixed cut-off can throw out good eggs in a cool month and keep weak ones in a hot month.
So work out the median of each tray, which is the middle egg when you line the weights up in order. Then sort every egg against that median.
| Band | Distance from the tray median | What we do with it |
|---|---|---|
| Core | Within about 5 percent | Set in the main machine |
| Edge | Between 5 and 10 percent off | Set in a separate, labelled tray, or keep for the kitchen |
| Outlier | More than 10 percent off | Do not set. Use for food or sell as table eggs at a lower price |
The 5 percent core band is a working rule from our own sorting, not a law of physics. A very tight tray can justify a slightly wider core. A tray that spreads widely is telling you something about the flock, and sorting will only hide that problem for one set.
Why light eggs and heavy eggs both cause trouble
Small eggs usually come from young hens still finding their rhythm, or from hens stressed by heat, disease or a sudden change of feed. The embryo inside has less yolk to start from. Chicks that do hatch from light eggs tend to be small, slow to dry and slow to reach the feeder, and they often sit in the bottom of the box while the rest of the hatch runs.
Heavy eggs fail in a different way. Very large eggs from mature hens are where double yolks tend to show up, and a double-yolked egg almost never gives you a healthy chick. Oversized single eggs carry more yolk and albumen than a chick can use neatly. The chicks that come from them can be big, hard to pull through the shell, and slow to pip.
The lesson is not that small is bad and big is good. The lesson is that one odd egg in the tray works against the rest of the set, and the machine cannot tell them apart.
Check shape second, because weight and shape argue
Shape is easy to see and easy to over-rate. A pointed egg looks wrong, but it may weigh the right amount and hatch perfectly well. The combination is what matters. A long, narrow egg that weighs like the core of the tray has less room for its contents than a fat egg of the same weight. Round, lumpy or thin-shelled eggs often weigh strangely for their length, which is why we look at shape only after the weighing is done.
Check by sight and by feel. Roll each egg across a flat tray and listen for a clean, even stop. Hold it to a torch and look at both ends. For a number, use the shape index, the width divided by the length, expressed as a percentage. For chicken eggs the usual range sits somewhere around 72 to 76 percent. You do not need to measure every egg. Measure a handful when a tray looks odd, and set the ones that look and weigh normal.
- Reject eggs that are very round, very pointed, or carry a ridge or a dent.
- Reject cracked eggs, shell-less eggs and eggs with sandy or chalky shells, whatever they weigh.
- If shape faults turn up in more than a few eggs from one tray, write it down. It usually points at the flock, not the machine.
A weight loss target that turns weighing into a plan
An egg in the setter gives up water through its shell all the time. By the time you move the eggs to the hatcher, that loss is part of the plan. For chicken eggs, a loss of roughly 12 to 13 percent by day 18 is the range most hatcheries work to. Too little loss usually means the air has been too humid. Too much means it has been too dry, or the eggs have been sitting hot.
Here is a worked example. A 61 gram egg should lose about 7.6 grams by day 18 at 12.5 percent. That leaves roughly 53.4 grams at transfer. If it reads 56 grams, the egg is holding its water and the room is probably too humid. If it reads 49 grams, the egg has lost too much, and the next set needs more moisture in the machine.
You do not need to weigh the whole tray. Weigh five or six core eggs on day 1, mark them, and weigh the same eggs again at transfer. The sample tells you whether the room is doing what you think it is doing, and it costs you ten minutes. If you would rather hand the setting to someone with a machine already tuned, our egg hatching service covers that.
Sorting a tray in about ten minutes
- Clear the table, wipe the scale, and switch it on for a minute before you start.
- Check the scale against the reference weight and write the reading down.
- Weigh each egg and call the number out to whoever is writing on the tray map.
- Find the median by lining the weights up in order and taking the middle value.
- Mark each egg core, edge or outlier against that median.
- Check shape and shell on the core and edge eggs only, by sight and by rolling.
- Load the core eggs pointed end down, and label the tray with date, source flock and median.
- Put edge eggs in their own labelled tray, and take outliers out of the setting room.
Two people work this best. One weighs and one writes. A single person doing it alone takes longer, and the mistakes creep in near the end of the tray, when the hands are tired and the numbers start to blur together.
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What to write down so the weights mean something later
A weight sort only teaches you something if you can see the result afterwards. Keep one line per tray and fill in the hatch when the chicks are out. After a few months the pattern shows, and you stop guessing about which band to trust.
| Field | What to write | Why it helps later |
|---|---|---|
| Date collected and date set | Both dates, as numbers | Shows storage age, the first thing to check in a poor hatch |
| Source flock | Flock name or number and the age of the hens | Lets you compare flocks side by side |
| Tray median and spread | Median to 0.1 g, lowest and highest weight | Shows whether a wide spread went with a weak hatch |
| Eggs in each band | Count of core, edge and outlier | Tells you how much you threw away, and from which flock |
| Weight at transfer | Five or six sample eggs, average loss | Confirms whether humidity was right |
| Chicks hatched and first notes | Count on hatch day, plus anything odd | Closes the loop between weight and result |
When weight is the wrong thing to check
Weight cannot tell you whether an egg is fertile, which is its biggest limit. A perfectly sized egg can be infertile, and an odd-looking egg can carry a healthy embryo. Use weight to make the set uniform, then use fertility checks to decide what the set is worth. Our guide to testing egg fertility before you set covers that second job in detail.
Weight also misleads with eggs from a flock that has just come into lay. The first eggs are small, and the weights climb over several weeks. If you are buying from a young flock, put the first week's eggs in their own tray or hold them back until the weights settle. Do not blend them into a set you expect to hatch evenly.
If you are buying eggs, weigh a sample on arrival
Eggs lose weight on the road, mostly through water loss in a hot vehicle, and they can arrive light enough to drop into the wrong band even if they left the farm in the right one. Weigh a sample from the first box you open, and compare it with any weights the seller gave you. A small gap is normal. A large gap usually means the eggs sat too long or too hot, and that is a conversation to have before you pay the balance. Our shipping guide for fertile eggs explains how to keep that gap small.
Ask the seller what weight range they supply and whether they will weigh a sample before dispatch. Routes and costs are set out on our delivery page, and you hear the delivery cost before any money changes hands. To talk through a tray before ordering, send a note to +233 24 915 1503 on WhatsApp, then use the order form when you are ready.
Questions farmers ask
What weight should a chicken hatching egg be?
There is no single correct weight for every flock. Parent flocks differ by breed and age, and the breeder's guide gives the target band for its own birds, so start there. On your own farm the useful target is the tray median and how tightly the eggs cluster around it. Sort by that, and use the breeder's band as a sense check.
Should I set small eggs if they are all I have?
You can, but expect a slower, less even hatch and smaller chicks. Keep the small eggs in a separate, labelled tray so their results do not get mixed with the core eggs. If the whole set is small, record the median and the hatch honestly, and work out whether the flock needs attention before you buy again. Our <a href="/faq/">questions page</a> has the early-chick basics if you need them.
Can weight tell me whether an egg is fertile?
No. Weight tells you about size and the water the egg will lose, not about whether an embryo ever started. An egg in the core band can be infertile, and an edge egg can be fertile. Fertility needs a separate check, usually candling at around day 7 or a test set.
How do I work out the weight loss for a set?
Multiply the egg's day 1 weight by your target loss, about 0.12 to 0.13 for chicken eggs, to get the grams to lose by day 18. Subtract that from the day 1 weight to get the expected weight at transfer. Compare five or six marked eggs against that figure, and adjust humidity for the next set.
Can I mix eggs of different weights in one setter?
Yes, if they are all in the core band, which is what the machine is designed for. Keep edge eggs in their own labelled tray, and do not put outliers in the setter at all. A tray of mixed weights hatches unevenly even when every egg is fertile.
Should I weigh eggs at collection or just before setting?
Both, if you can. The collection weight is your first sort. Eggs lose water in storage, so weigh again just before setting and move any egg that has drifted into the edge band. Write both numbers down so you can see how much your store is costing you.
Are round or pointed eggs always rejected?
Not always, but they deserve a closer look. A lightly pointed egg of the right weight usually hatches. A very round or very pointed egg, or one with a ridge, is a reject in our book, because that shape often comes from a rushed lay or a shell problem in the hen.
