Quick Answer
It works as a guide to age, not safety. As an egg ages its air cell grows, so a fresh egg sinks and lies flat, an older one stands up and a very old one floats. British Lion eggs says to avoid eating eggs that float, but the test cannot show whether an egg is safe, so always check the best-before date too.
Key Takeaways
- The best-before date is the first check, and the float test is a back-up. UK law sets the date no more than 28 days after laying.
- The float test measures how much air has entered the egg. It says nothing about bacteria, cracks or how the egg was stored.
- Cracking an egg into a separate bowl is the check that catches real spoilage: a sulphur smell, or a pink, green or iridescent white.
How do you check an egg is fresh? Start with the date
How do you check an egg is fresh? Before the water test, look at the date. Which? notes that government advice is to stick to the best-before date when deciding whether to eat eggs, and that while several cookery experts and organisations, including the RSPCA and the British Egg Industry Council (BEIC), suggest the float test as an indication of freshness, none advocate using it after the best-before date.
Egg freshness dates explained
Eggs sold in the UK carry a best-before date, not a use-by date. According to Trading Standards guidance on Business Companion:
- the best-before date must be no more than 28 days after the date of laying
- retailers must sell eggs within 21 days of laying
- there is no legal requirement for a sell-by or display-until date
- packs can be labelled “extra” or “extra fresh” only until nine days after laying
- packs must carry the storage instruction “keep refrigerated after purchase”
All British Lion eggs, BEIC says, have the best-before date printed on the shell as well as on the box.
A best-before date is about quality, not strict safety. The Food Standards Agency (FSA) revised its advice on eggs in 2011: as reported at the time, eggs can be eaten a day or two after the date provided they are cooked thoroughly until the yolk and white are solid, or used in dishes that are fully cooked, such as cakes. Renfrewshire Council’s egg safety page repeats this advice. Food Standards Scotland says that after the date the quality of the egg declines and any salmonella present could multiply. Check the current FSA page before relying on the “day or two” allowance.
How to read egg carton expiration dates
Look for “Best before: day / month / year” on the box. Some packs also show a packing or laying date. The stamp on the egg itself carries a code: the first digit shows how the hens were kept (0 organic, 1 free range, 2 barn, 3 cage), followed by UK and a production site number. Our guide to brown eggs and white eggs explains the codes in full.
How long do raw eggs last in fridge conditions?
In the UK, the best-before date is the guide: up to 28 days from laying, and most of that is used up before the eggs reach you, as shops must sell them within 21 days. Which? says Lion eggs are typically delivered to supermarkets within 48 hours of laying, because producers must collect them at least twice a week. We found no UK source giving a fixed number of weeks once an egg is in your fridge, so follow the date on the box.
Egg freshness test water method: step by step
The egg freshness test water method is simple, and it comes from the British Lion eggs website. We have not run our own photographed test for this article.
- Fill a large bowl or mixing bowl with cold water.
- Gently lower the egg in. Test each egg separately.
- Read the result:
- Sinks and lies on its side: fresh.
- Sinks but stands up straight: semi-fresh.
- Floats higher than halfway towards the surface: older. British Lion eggs says it is “most definitely not fresh” and consumption should be avoided.
- Dry the egg, and wash your hands and the bowl afterwards. BEIC advises washing hands before and after handling eggs.
How to check egg freshness in water is quick, but it needs the right interpretation, as the next section shows.
Egg float test meaning: what floating, tilting and sinking show
What causes eggs to float?
The older an egg is, the more air seeps through the shell and gradually makes it more buoyant, according to British Lion eggs. As an egg ages, moisture leaves it and air enters through tiny pores in the shell, enlarging the air cell at the wide end. A big enough air cell makes the egg float.
Does a sinking egg mean good or bad?
A sinking egg is a fresher egg, but sinking does not prove an egg is safe. The US Egg Safety Center, quoted by one egg-keeping blog, notes that a freshly collected egg from a dirty nest box can harbour salmonella and still sink. Eggs that are dirty, cracked or broken should not be used at all, BEIC says. That is why the date, the condition of the shell and cooking all still matter.
Egg float test reliability: how far can you trust it?
It is a fair guide to age and an unreliable guide to safety. BEIC treats a floater as one to avoid. US sources, including the Egg Safety Center, say that a floating egg is older but not necessarily unsafe, and that the test is not an indicator of safety. We follow the UK advice: if an egg floats, do not use it. If it sinks, do not treat that as a safety guarantee.
Cracking and looking
How to tell if an egg is bad when cracked
Crack the egg into a separate bowl, not straight into the pan or mixture. WebMD, a US health site, says a fresh egg has little or no smell, whereas one that is going bad smells like sulphur.
Bad egg smell test
A sulphur or sour smell as soon as the shell is broken means bin it. Smell is useful for spotting spoilage, but it cannot detect everything. Falkirk Council’s environmental health officers say you cannot see, taste or smell food poisoning bacteria, which is why dates and thorough cooking matter.
What does a bad egg look like inside?
WebMD says an egg white that is green or iridescent may contain harmful bacteria, and pink white is another warning sign. Throw out any egg like this.
Some features that look odd are normal:
- Cloudy white: a sign the egg is very fresh, caused by carbon dioxide that has not yet escaped.
- White strings in the white: these are chalazae, which anchor the yolk, and they do not need to be removed.
- Green-grey ring around a boiled yolk: caused by overcooking, which affects appearance rather than safety.
Checking egg white consistency
A fresher egg has a thicker white that sits close to the yolk, while an older egg spreads out and has a runnier white. This tells you about age, not spoilage. A runny white with no smell and no discolouration is just an older egg, based on poultry industry advice, not UK guidance.
Testing eggs for baking
Age matters differently for different jobs. Which? notes that freshness can make a difference to a recipe, for example when poaching an egg or baking a cake. American sources say older whites whip up more easily for meringues, while freshness makes little difference to how a cake rises. BEIC adds that eggs at room temperature can be beaten to a greater volume, so do not whisk eggs straight from the fridge.
Storing eggs
BEIC’s advice:
- keep eggs in their original box on a shelf in the fridge, not loose in the door
- store them at a constant temperature below 20°C, with the fridge best in a domestic kitchen
- keep them away from strong-smelling food, as shells are porous
- keep them away from raw meat
- store and use them in date order
- never use dirty, cracked or broken eggs
- take them out of the fridge about half an hour before cooking for baking
If you have too many, BEIC says you can freeze them: crack them into a container or ice cube tray (not in the shell). For cooked eggs, see our guide to how long boiled eggs keep in the fridge.
Frequently Asked Questions
Does the egg float test really work?
As a guide to age, yes. A fresh egg sinks, an older one tilts and a very old one floats. It does not tell you whether an egg is safe, so check the best-before date, the shell and what is inside when you crack it.
How to tell if an egg is good or bad without breaking it?
Check the best-before date and the shell: do not use dirty, cracked or broken eggs. The water test then shows age. If the egg floats higher than halfway, British Lion eggs says to avoid eating it. Cracking it open is the only way to check smell.
Does a sinking egg mean good or bad?
A sinking egg is fresher, but that is not a safety guarantee. An egg can sink and still be cracked, dirty or badly stored. Use the date, the condition of the shell and thorough cooking, as the FSA advises, as well as the test.
How to tell if an egg is bad when cracked?
Crack it into a separate bowl. Bin it if it smells of sulphur or has a pink, green or iridescent white. A cloudy white is a sign of freshness, and a runny white means only that the egg is older.
What does a bad egg look like inside?
A white that is pink, green or iridescent is a warning sign, according to WebMD. Often there is also a strong sulphur smell. Cloudy whites, white strings and a green ring on a boiled yolk are normal.
Does the float test show an egg’s expiration date?
No. Eggs have a best-before date, which is no more than 28 days after laying. The float test shows how much air has entered the egg, which suggests age, but it cannot tell you the date or whether the egg is safe.
