You can test an egg’s freshness by placing it in a bowl of water. A fresh egg will sink and lie flat on its side. An older egg will stand upright on one end, and a bad egg will float to the surface. The float test is a quick and reliable way to check if an egg is still good to eat, but it does not tell you everything about food safety.
Why Do Bad Eggs Float in Water?
The science behind the float test comes down to the shell and the air cell inside the egg. Every egg has a small air pocket between the shell and the inner membrane. As the egg ages, moisture and carbon dioxide escape through the porous shell. The contents shrink, and the air cell grows larger. A bigger air cell means more buoyancy. When the air cell becomes large enough, the egg will float.
A fresh egg has a tiny air cell. It sinks and rests on its side. After a week or so, the air cell expands enough that the egg will stand upright on the bottom of the glass. By the time the egg is several weeks old, the air cell is large enough to lift the egg off the bottom entirely. That floating egg is old, and it may be spoiled.
The float test works because the shell is porous. It is not a myth. The same principle explains why eggs lose weight over time in the refrigerator. The water loss is gradual, and the air cell grows in proportion to the age of the egg.
How to Do the Float Test Correctly
Fill a bowl or glass with cold water. The water should be deep enough that the egg has room to move. Gently lower the egg into the water. Do not drop it, because a cracked shell will let water inside and change the result.
Watch what the egg does. There are three possible outcomes.
It sinks and lies flat. The egg is fresh. The air cell is small, and the egg is safe to use for any recipe.
It sinks but stands upright. The egg is older but still safe to eat. It is not ideal for poaching or soft boiling, because the white will be thinner and spread out. It is fine for baking, scrambling, or hard boiling.
It floats. The egg is old. It may be spoiled. Do not eat it. Throw it away.
The float test takes less than a minute. It is one of the simplest kitchen tests you can do, and it requires no special tools.
Does the Float Test Prove an Egg Is Safe to Eat?
No. The float test tells you about age, not safety. A floating egg is almost certainly too old to use, but a sinking egg is not automatically safe. Eggs can spoil before the air cell grows large enough to make them float. Bacteria can get through tiny cracks in the shell that are hard to see. If an egg has an unusual smell, a strange color, or a slimy texture, throw it away regardless of what the float test shows.
The best practice is to use the float test together with your other senses. Crack the egg into a separate bowl. Look at the white and yolk. A fresh egg has a thick white that holds together and a yolk that sits high and round. An older egg has a thinner white that spreads out and a yolk that flattens. Smell the egg. A bad egg has a distinct sulfur smell that is hard to miss. If anything seems off, do not use it.
The float test is a useful screening tool, but it is not a guarantee. Food safety always comes down to multiple checks.
How Long Do Eggs Last in the Refrigerator?
Eggs last longer than most people think. Stored in the refrigerator at a consistent temperature, eggs typically remain good for three to five weeks from the date they were packed. The “sell by” date on the carton is not an expiration date. It is a guide for the store, not for your kitchen.
The key is temperature. Eggs should be kept in the main body of the refrigerator, not in the door. The door opens and closes constantly, which causes temperature swings. The main shelves stay colder and more stable. Keep eggs in their original carton. The carton protects them from absorbing strong odors from other foods and helps prevent moisture loss.
If you are unsure how old your eggs are, the float test gives you a quick answer. A fresh egg sinks. An older egg stands up. A bad egg floats. This simple test can save you from cracking open a spoiled egg into your pancake batter.
Can You Eat Eggs Past the Sell-By Date?
Yes, in most cases. The sell-by date is not a safety deadline. Eggs that have been properly refrigerated can be eaten for several weeks after that date. The float test is a better indicator of freshness than any date printed on the carton.
That said, there are limits. If an egg floats, it is too old. Do not risk it. The cost of throwing away one egg is far less than the cost of food poisoning. Salmonella is a real risk with eggs, and it can cause serious illness. Older eggs are more likely to harbor bacteria because the protective coating on the shell breaks down over time.
Use the float test as your first check. If the egg floats, discard it. If it sinks, crack it into a bowl and inspect it. Trust your nose. A bad egg smells terrible, and that smell is a clear signal that the egg is not safe to eat.
Do Farm-Fresh Eggs Float Differently?
Farm-fresh eggs and store-bought eggs behave the same way in water. The float test works on all chicken eggs regardless of where they came from. The difference is the timeline. Farm-fresh eggs that have not been washed have a natural protective coating called the bloom. This coating seals the pores in the shell and keeps the egg fresher for longer. Store-bought eggs are washed to remove dirt and bacteria, but this washing also removes the bloom. That is why store-bought eggs need refrigeration, while farm-fresh eggs can sit on the counter for a short time.
The float test is still valid for farm eggs. A farm egg that floats is old and should not be eaten. The bloom slows down the aging process, but it does not stop it. Eventually the air cell grows, and the egg will float just like any other old egg.
What If the Egg Cracks During the Test?
If an egg cracks while you are testing it, the result is unreliable. Water can enter through the crack, which will make the egg sink even if it is old. A cracked egg should be used immediately or discarded. Bacteria can enter through the crack, and the egg may not be safe to keep.
If you crack an egg and water gets inside, the egg is no longer good for storage. Use it right away if it smells fine, or throw it out if you have any doubts. Do not put a cracked egg back in the refrigerator.
Does the Float Test Work for Other Eggs?
The float test can be used for duck eggs, quail eggs, and other poultry eggs. The same principle applies. The air cell grows as the egg ages, and older eggs float. The timeline may differ because different birds lay eggs with different shell thickness and porosity, but the basic test works the same way.
For duck eggs, which have thicker shells, the float test still works but the air cell grows at a different rate. If you raise your own poultry, the float test is a handy tool for checking the age of your eggs.
Other Ways to Check Egg Freshness
The float test is not the only way to check an egg. You can also shake the egg gently near your ear. A fresh egg makes almost no sound. An older egg has more liquid inside and will make a sloshing sound. This method is less reliable than the float test, but it can give you a rough idea.
You can also hold the egg up to a bright light. This is called candling. In a dark room, a bright flashlight can reveal the size of the air cell. A large air cell means an older egg. Commercial egg producers use candling to grade eggs, but it works at home too.
The most reliable test is still cracking the egg open. Look at it, smell it, and cook it. Your senses are the final judge.
How to Store Eggs to Keep Them Fresh Longer
Proper storage extends the life of your eggs. Keep them in the refrigerator at a temperature below 40°F. Store them in the original carton on a middle shelf. Do not wash eggs before storing them. Washing removes the protective coating and makes the eggs more vulnerable to bacteria.
Keep eggs away from strong-smelling foods like onions and fish. The shell is porous, and eggs can absorb odors. The carton helps with this, but it is not a complete barrier.
If you have more eggs than you can use before they go bad, you can freeze them. Crack the eggs into a bowl, beat them lightly, and pour them into a freezer-safe container. Frozen eggs can last for months. Do not freeze eggs in the shell. The liquid expands when frozen and will crack the shell.
Frequently Asked Questions
Is the float test always accurate for telling if an egg is bad?
No. The float test is a reliable indicator of age, but it does not guarantee safety. A sinking egg can still be spoiled, so always check the smell and appearance after cracking.
How long can eggs stay in the refrigerator before they go bad?
Eggs typically stay good for three to five weeks from the pack date when refrigerated properly. The sell-by date is not an expiration date, and the float test is a better freshness guide.
Can you eat an egg that stands upright in water?
Yes. An egg that stands upright on the bottom is older but still safe to eat. It is best for baking or hard boiling rather than poaching, because the white is thinner.
What should you do if an egg floats in the water test?
Throw it away. A floating egg is old and may be spoiled. Do not crack it open to check, because the smell and bacteria can contaminate your kitchen surfaces.
