How to Choose Eggs: What the Shell Code and the Carton Actually Tell You
Compiled and fact-checked from cited sources, reviewed by our editorial team. · Last updated:
Only one thing on the shelf gives you real information about an egg: what is printed on it. Everything on the front of the box — “farm fresh”, “natural”, “premium” — is marketing. The stamp on the shell, or the code on the carton, is regulated.
The second thing worth knowing before you shop: whether the eggs sit in a chiller or on an ambient shelf is not a quality signal. It follows from one thing only — whether your country washes its eggs. That single decision explains almost every difference between how eggs are sold in Britain and how they are sold in the United States.
Get those two ideas straight and the rest of the aisle becomes easy.
Reading the code: UK and EU
Every egg sold in the UK and the EU carries a stamp. It looks like this:
1 UK 54321 or 1-DE-0123456
| Part | What it tells you |
|---|---|
| First digit | How the hen was housed (0, 1, 2 or 3) |
| Country letters | Country of origin |
| Remaining digits | The specific farm and shed |
The first digit
- 0 — Organic. Organic feed, outdoor access, organic certification rules.
- 1 — Free-range. Continuous daytime access to outdoor runs.
- 2 — Barn. Indoors, but cage-free, able to move around the floor.
- 3 — Cage. Housed in enriched cages with restricted movement.
The digit describes housing, not nutrition. An organic egg and a cage egg from hens on similar feed differ far less nutritionally than the price gap suggests. What the digit genuinely buys you is a welfare standard.
In the UK, a British Lion mark on the shell is a separate thing again: it certifies that the hens were vaccinated against Salmonella Enteritidis and that the eggs meet an industry food-safety code. That mark, not the housing digit, is what changed official advice on runny eggs for vulnerable groups.
Reading the carton: United States
The US does not use the 0-3 code. American cartons carry four different pieces of information.
Grade (AA, A or B). This is about appearance and the interior when the egg is broken out, not safety or nutrition. Grade AA has a firmer white that spreads less; Grade A is slightly less firm and is what most supermarkets stock; Grade B eggs usually go to processing, not to shelves.
Size. Sized by weight per dozen, not per egg: Medium 21 oz, Large 24 oz, Extra Large 27 oz, Jumbo 30 oz. Recipes assume Large.
Julian pack date. A three-digit number from 001 to 365 showing the day of the year the eggs were packed. 045 means 14 February. This is the most useful number on the carton and most shoppers walk straight past it.
Plant code. Begins with P, identifies the packing facility. Useful only if there is a recall.
The sell-by or expiration date may be at most 30 days after the pack date, so two cartons with the same sell-by date can differ by weeks in actual age. Compare Julian dates, not sell-by dates.
Chiller or shelf: it depends on washing
This is the single most misunderstood thing about eggs, and it has one cause.
When a hen lays an egg, the shell carries a thin natural coating called the cuticle or bloom. It keeps bacteria out while letting the egg breathe.
- The UK and EU do not wash eggs. The cuticle stays intact, so eggs can be sold at ambient temperature. A shelf display is the system working as designed, not a lapse.
- The US, Canada, Japan and Australia wash eggs. Washing removes the cuticle, so those countries require refrigeration from packing to purchase.
The practical rule is the same everywhere: buy them at the temperature they are being kept, and keep them that way at home. Moving eggs back and forth is what causes trouble. A cold egg brought into a warm room sweats, and that moisture film helps bacteria cross the shell.
Never wash eggs at home before storing them. Scrubbing a dirty-looking egg under the tap removes the cuticle that is protecting you, and the water can be drawn in through the pores. Wipe visible dirt off with a dry cloth. If an egg genuinely needs washing, wash it immediately before cooking — never before storage.
The five-second check at the shelf
1. Open the box and look. One cracked, chipped or leaking egg and you put the whole box back. A crack removes every bit of protection the shell provides.
2. Nudge each egg. An egg stuck to the carton has leaked through a crack you cannot see.
3. Check the date. In the EU and UK the best-before date is 28 days from laying. In the US, read the three-digit Julian pack date instead of the sell-by date.
4. Pick the size you actually need. In the UK and EU: Small under 53 g, Medium 53-63 g, Large 63-73 g, Very Large over 73 g. Recipes assume Medium in Britain and Large in the US — which are close in weight, and which is why British and American recipes usually interchange without trouble.
5. Think in price per kilo. A box of very large eggs and a box of small eggs are not comparable per egg. Compare the same size class.
Which egg for which job
The least-known and most useful part of choosing eggs.
Boiling: choose older eggs. This sounds wrong and is correct. In a very fresh egg the membrane clings tightly to the shell, and peeling tears the white apart. An egg that is one to two weeks old peels cleanly. If you are buying today to boil tomorrow, reach for the box with the earliest date, not the latest.
Poaching: choose the freshest. The opposite applies. A fresh white is thick and holds together in the water. An older white has thinned and will spread into wisps.
Frying: either works. Only the shell needs to be intact.
Baking: Large, at room temperature. Recipes are built around that weight, and eggs taken out of the fridge 30 minutes earlier emulsify into butter far better.
Whisking whites: slightly older eggs. A thinner white whips more easily and to greater volume.
Two myths worth dropping
Shell colour tells you nothing. Brown eggs are not more natural, more nutritious or better quality than white ones. Shell colour is determined by the breed of hen. Where brown eggs cost more, it is because the breeds that lay them tend to be larger birds that eat more — plus consumer expectation.
Yolk colour is about feed, not nutrition. A deep orange yolk means the hen’s feed was rich in carotenoids — maize, marigold extract, paprika. Producers can and do adjust this deliberately. A dark yolk looks more appetising, but on its own it does not mean a more nutritious egg.
Buying direct from a farm
Small producers may not stamp their eggs, so different checks apply.
- Look at where the hens live. Dry, clean ground and orderly feeders and drinkers tell you more than any label.
- Ask when they were collected. The difference between this morning and last week decides whether they are better for poaching or for boiling.
- See how they are being kept. Walk away from eggs sitting in the sun.
- Ask whether they have been washed. Washed eggs now need refrigeration; unwashed ones do not.
- A little dirt or a feather is normal on an unwashed egg and is not a fault.
Once you get them home
- Store them pointed end down. The air cell sits at the blunt end; pointing the egg down keeps the yolk centred and the egg good for longer.
- Keep them out of the fridge door. The door is the part of the fridge whose temperature swings most. Eggs belong on a shelf inside.
- Leave them in the carton. It protects them from knocks and stops the porous shell absorbing the smell of onions and cheese.
- Cracked-out eggs go in a sealed container and last two days in the fridge, no more.
Whether an egg you already own is still good is a separate question with its own tests — the float test, the smell, the shake.
Frequently asked questions
How do I choose eggs? Read the stamp or the carton code first, then open the box and check for cracks, then look at the date, then pick the size the recipe needs.
How can I tell a good egg at the shop? Only a few things are visible there: an intact clean shell, a recent date, no leaks in the box. Freshness tests are done at home, not in the aisle.
What do 0, 1, 2 and 3 mean on an egg? Organic, free-range, barn and cage housing respectively. The digit describes how the hen was kept.
Which code is best? For animal welfare, 0 and 1 describe better conditions. Nutritionally the differences are much smaller than the price gap implies, and feed matters more than housing.
What is the three-digit number on a US carton? The Julian pack date — the day of the year the eggs were packed, from 001 to 365. It is more informative than the sell-by date.
What does Grade AA mean? A firmer white and a rounder yolk when broken out. It is an appearance standard, not a safety or nutrition one.
Should eggs be refrigerated? In the US, Canada, Japan and Australia, yes — they are washed. In the UK and EU they need not be, because they are not washed. Either way, be consistent and do not move them between temperatures.
Why are eggs on an open shelf in Europe? Because they are unwashed and retain their protective cuticle, so ambient storage is safe.
Should I wash eggs? Not before storing. Washing removes the cuticle and can draw water through the shell. Wipe dry, and wash only immediately before cooking if you must.
Are brown eggs healthier than white? No. Shell colour depends on the breed of hen and has no bearing on nutrition.
Is a darker yolk better? It means more carotenoids in the feed. It looks richer but does not by itself mean a more nutritious egg.
Which eggs should I buy for boiling? Ones that are one to two weeks old. Very fresh eggs are notoriously hard to peel.
Which eggs for poaching? The freshest you can get, so the white holds its shape.
What size do recipes mean? Medium in the UK and EU, Large in the US. The two are close enough in weight to swap.
How long do eggs keep? In the EU and UK the best-before date is 28 days from lay. In the US, up to 30 days from the pack date, refrigerated.
How should I store them? Pointed end down, in their carton, on an inside shelf rather than the door.
Sources
- British Lion Eggs — the stamped code, the Lion mark and what each element means. https://www.egginfo.co.uk/british-lion-eggs
- USDA FSIS — Shell eggs from farm to table (grades, sizes, Julian dates, refrigeration). https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/eggs/shell-eggs-farm-table
- USDA ARS — why the US washes eggs and what the cuticle does. https://tellus.ars.usda.gov/stories/articles/how-we-store-our-eggs-and-why/
- FDA — What you need to know about egg safety. https://www.fda.gov/food/buy-store-serve-safe-food/what-you-need-know-about-egg-safety