You are preparing breakfast and decide to test your eggs by placing them in a bowl of water. Most of the eggs sink, but one slowly rises and floats at the surface.
Social media posts often claim that a floating egg is rotten and must be thrown away immediately. Others insist that the test reveals only the egg’s age and that it may still be safe to cook.
Who is right?
A floating egg is generally an older egg, but floating does not automatically prove that it is spoiled or unsafe. As an egg ages, moisture and carbon dioxide escape through tiny pores in the shell, causing the air cell inside to become larger. The bigger air pocket makes the egg more buoyant.
The water test may provide a rough indication of age, but it cannot detect harmful bacteria or guarantee food safety. Storage conditions, shell integrity, odor, appearance, and proper cooking matter more.
What Is the Egg Float Test?
The egg float test is a traditional kitchen method used to estimate an egg’s relative age.
To perform it, people place an uncracked egg in a bowl or glass of cold water and observe its position.
The results are usually interpreted this way:
An egg that lies flat on the bottom is relatively fresh.
An egg that remains on the bottom but stands upright is older.
An egg that floats has a larger internal air cell and is considerably older.
This test can demonstrate a physical change that occurs over time, but it is not a laboratory food-safety test.
It cannot tell you whether an egg contains Salmonella, whether it was kept continuously refrigerated, or whether microorganisms entered through a damaged shell.
Why Do Old Eggs Float?
Eggshells may appear solid, but they contain thousands of microscopic pores.
After an egg is laid, moisture and carbon dioxide gradually escape through these pores. Air moves into the shell, and the air cell at the egg’s wider end grows larger.
A fresh egg contains a relatively small air pocket, so it usually sinks and lies flat.
As the egg ages:
Moisture slowly leaves the egg.
Carbon dioxide escapes.
The contents shrink slightly.
The internal air cell expands.
The egg becomes more buoyant.
Eventually, the air pocket may become large enough to make the egg stand upright or float.
The result mainly tells you that the egg has aged. It does not explain how the egg was stored or whether it contains harmful bacteria.
Does a Floating Egg Mean It Is Rotten?
No. Floating and rotting are not identical.
A floating egg may still be usable if it has been properly refrigerated, the shell is intact, and the egg shows no spoilage signs after being cracked into a separate bowl.
However, a floating egg is older and deserves closer inspection. Its quality may have declined, even if it has not become spoiled.
An old egg may have:
A thinner, more watery white
A flatter yolk
Reduced ability to hold its shape
Lower quality for frying or poaching
Greater suitability for hard-boiling
If the egg produces an unmistakably unpleasant odor when cracked, discard it immediately.
When you cannot confirm how the eggs were stored—or if the person eating them is at increased risk from foodborne illness—the cautious choice is to throw away a questionable egg.
Can a Fresh-Looking Egg Contain Salmonella?
Yes.
An egg can look, smell, and behave normally in water while still containing harmful bacteria. The float test cannot detect Salmonella or other pathogens.
Bacteria may sometimes be present inside an egg before the shell forms. Contamination can also occur on the outside of the shell.
This is why every egg should be handled as a perishable food, even if it sinks during the water test.
Safe refrigeration and thorough cooking are more important than whether the egg floats.
What Does Each Position in Water Mean?
The Egg Lies Flat on the Bottom
This usually indicates a relatively fresh egg with a small air cell.
It may work well for frying, poaching, baking, or other recipes where the egg’s shape and structure matter.
Sinking does not guarantee that it is free from harmful bacteria.
The Egg Tilts Upward
An egg that remains underwater but tilts upward is older than one lying completely flat.
It may still be suitable for cooking if it was stored properly and has no spoilage signs.
The Egg Stands Upright on the Bottom
A standing egg has a larger air cell and has likely been stored longer.
Crack it into a separate bowl before combining it with other ingredients. Discard it if the odor or appearance is abnormal.
The Egg Floats at the Surface
A floating egg is relatively old because its air cell has grown.
Floating alone does not prove spoilage, but the egg should be evaluated carefully. If its storage history is unclear, its shell is damaged, or you are uncomfortable using it, discard it.
No egg is valuable enough to justify taking an unnecessary risk.
Why the Float Test Cannot Confirm Safety
The test measures buoyancy, which is influenced primarily by the amount of air inside the shell.
It does not measure:
Bacterial contamination
Refrigerator temperature
Time spent at room temperature
Shell cleanliness
Invisible shell damage
The presence of Salmonella
Whether the egg was washed or handled properly
How long the carton remained unrefrigerated
A sinking egg can be contaminated, and a floating egg may simply be old.
The float test should therefore be treated as an informal freshness estimate—not a pass-or-fail safety test.
How to Check a Questionable Egg Safely
If an egg floats but has otherwise been properly refrigerated, inspect it carefully before deciding whether to use it.
Step 1: Examine the Shell
Do not use an egg with:
Cracks
Leaking contents
A slimy shell
Powdery mold
Severe dirt or contamination
An unusual bulge or damaged area
Bacteria may enter more easily through a compromised shell.
Step 2: Crack It Into a Separate Bowl
Never crack a questionable egg directly into cake batter, a skillet filled with other eggs, or a mixture containing expensive ingredients.
Use a small clean bowl so that you can discard the egg without contaminating the rest of the food.
Step 3: Check for an Unpleasant Odor
A spoiled egg usually produces a strong, unmistakable odor when the shell is broken.
If it smells rotten, sulfurous, or otherwise abnormal, discard it and clean the bowl.
Do not taste the egg.
Step 4: Examine Its Appearance
An older egg often has a thin white and a flatter yolk. Those changes concern quality and do not automatically indicate spoilage.
Discard the egg if you notice mold, unusual iridescent coloring, or clearly abnormal contents.
Step 5: Cook It Thoroughly
If the egg appears normal and has been stored safely, cook it properly. People at higher risk of serious illness should consider using pasteurized eggs, particularly for recipes that are raw or lightly cooked.
How Long Do Eggs Last in the Refrigerator?
According to USDA storage guidance, raw shell eggs can generally be refrigerated for approximately three to five weeks after purchase when they are handled correctly.
The printed “sell by” or “expiration” date may pass during that period, but storage conditions remain crucial.
Keep the refrigerator at or below 40°F, or approximately 4°C.
The FDA recommends storing eggs in their original carton inside the main refrigerator compartment, not in the door. FDA egg-safety guidance
The carton helps protect the shells, limits odor absorption, and preserves the identifying information printed on the package.
Why You Should Not Store Eggs in the Refrigerator Door
Many refrigerators include a built-in egg tray in the door, but this is not the best location.
The temperature around the door changes whenever the refrigerator opens. Eggs stored there may repeatedly be exposed to warmer air.
An interior shelf generally maintains a more stable temperature.
Keep eggs:
In their original carton
On an interior refrigerator shelf
At 40°F or below
Away from strong-smelling food
Protected from cracks and impacts
Do not leave the carton on the counter while preparing a long meal. Remove only the eggs you need and return the carton promptly.
How Long Can Eggs Stay at Room Temperature?
Refrigerated eggs should not be left at room temperature for more than two hours.
When the surrounding temperature is above 90°F, that period decreases to one hour.
This includes time spent:
In a shopping cart
Traveling home
Inside a warm vehicle
On the kitchen counter
At a buffet or outdoor event
In the United States, commercially sold eggs are typically washed and refrigerated. Once refrigerated, they should remain cold because temperature changes can create condensation on the shell and potentially facilitate bacterial movement.
Should You Wash Eggs Before Refrigerating Them?
Commercially packaged eggs in the United States have already undergone regulated cleaning and processing. Washing them again at home is unnecessary.
Water can potentially move contamination around the kitchen, especially if eggs are washed in a sink also used for dishes or food preparation.
If an egg is cracked, leaking, or heavily contaminated, discard it rather than washing it for storage.
Wash your hands after touching raw eggs and clean surfaces contacted by the shell or contents.
Are Cracked Eggs Safe to Use?
Avoid purchasing cartons containing cracked eggs.
If an egg cracks on the way home, USDA guidance allows it to be broken into a clean container, covered, refrigerated, and used within a short period—provided you know exactly when and how it cracked.
However, discard an egg if:
It was already cracked at the store.
The crack’s age is unknown.
It leaked onto dirty surfaces.
The shell appears slimy or moldy.
It remained unrefrigerated.
It produces an abnormal odor.
Never use an egg with a damaged shell when you cannot verify its handling history.
Is a Blood Spot Inside an Egg Dangerous?
A small blood spot does not usually indicate that an egg is spoiled or fertilized.
Blood spots can occur when a tiny blood vessel breaks during egg formation. They are mainly a quality issue.
You may remove the spot with a clean utensil and cook the egg normally if everything else appears acceptable.
However, extensive unusual discoloration, mold, a rotten odor, or other abnormal characteristics justify discarding the egg.
What Does a Cloudy Egg White Mean?
A cloudy egg white is often associated with freshness.
Freshly laid eggs contain dissolved carbon dioxide, which can give the white a cloudy appearance. As the egg ages, carbon dioxide escapes through the shell and the white becomes clearer.
Cloudiness alone is not a spoilage sign.
A watery white, on the other hand, often indicates an older egg. It may spread farther in the pan, but that quality change does not automatically make it unsafe.
Why Do Some Hard-Boiled Eggs Peel More Easily?
Older eggs are often easier to peel after boiling.
As an egg ages, the air cell expands and the internal chemistry changes, reducing the attachment between the egg white and the inner shell membrane.
Very fresh eggs may therefore be frustrating to peel cleanly.
This is one reason eggs that stand upright—but remain submerged—may still be useful for hard-boiling if they have been stored correctly.
Again, easier peeling does not establish safety. Handle and cook the eggs properly.
How Should Eggs Be Cooked Safely?
The FDA advises cooking eggs until both the yolk and white are firm. Dishes containing eggs should generally reach an internal temperature of 160°F, or about 71°C.
Examples include:
Scrambled eggs
Casseroles
Breakfast bakes
Quiches
Custards
French toast
Stuffing containing eggs
Use pasteurized shell eggs or pasteurized egg products for foods that will be served raw or undercooked, such as:
Homemade Caesar dressing
Hollandaise sauce
Eggnog
Tiramisu
Raw cookie dough
Lightly cooked eggs for vulnerable individuals
Pasteurization reduces the risk from harmful bacteria without fully cooking the egg.
Who Is at Greater Risk From Undercooked Eggs?
Anyone can develop foodborne illness, but some groups face a higher risk of severe complications:
Children younger than five
Adults aged 65 and older
Pregnant people
People with weakened immune systems
Individuals undergoing certain medical treatments
For these groups, fully cooked or pasteurized eggs are the safer choice.
A runny egg may be a personal preference, but vulnerable people should understand the increased risk.
Can You Freeze Eggs in Their Shells?
Raw eggs should not be frozen in their shells because the contents expand and may crack the shell.
To freeze eggs:
Crack them into a clean bowl.
Gently mix the yolks and whites.
Pour the mixture into a freezer-safe container.
Label it with the number of eggs and date.
Freeze promptly.
Egg whites can also be frozen separately.
Hard-cooked whole eggs do not freeze well because the whites can become tough and watery.
How Long Do Cooked Eggs Last?
Hard-boiled eggs should generally be refrigerated and used within one week.
Cooked egg dishes and leftovers should be refrigerated promptly, usually within two hours, and stored in covered containers.
Do not leave deviled eggs, egg salad, casseroles, or other egg dishes at room temperature for extended periods.
When serving outdoors or at a buffet, keep cold egg dishes properly chilled and hot dishes at a safe holding temperature.
What If Someone Ate a Questionable Egg?
Eating an older or floating egg does not automatically cause illness. Monitor the person for symptoms such as:
Diarrhea
Stomach cramps
Nausea
Vomiting
Fever
Symptoms may begin within hours or take several days to appear.
Seek medical advice for bloody diarrhea, diarrhea lasting more than three days, high fever, frequent vomiting, dehydration, or severe symptoms. Pregnant people and individuals in other high-risk groups should seek help sooner.
The CDC’s food-poisoning guidance provides additional information about symptoms and when to contact a healthcare professional.
Frequently Asked Questions
Is it safe to eat an egg that floats?
A floating egg may still be usable if it has been properly refrigerated and shows no spoilage signs. Floating indicates age, not guaranteed spoilage or safety.
Why does a floating egg have more air?
Moisture and carbon dioxide gradually escape through the porous shell as the egg ages. The expanding air cell makes the egg more buoyant.
Can a sinking egg be bad?
Yes. Sinking does not prove that an egg is free from harmful bacteria or that it was stored properly.
Does a rotten egg always float?
A rotten egg may float, but not every floating egg is rotten. The test cannot provide a definitive safety result.
What should I do if an egg floats?
Inspect the shell and storage history. If you choose to examine it, crack it into a separate bowl and discard it if it smells or looks abnormal. When uncertain, throw it away.
How long can eggs remain in the refrigerator?
Properly refrigerated raw shell eggs can generally retain quality for three to five weeks after purchase.
Should I store eggs in the refrigerator door?
No. Keep them in their original carton on an interior shelf where the temperature remains more stable.
Can I eat eggs after the carton date?
They may still be usable when continuously refrigerated and free of spoilage signs, but date-label rules vary. Follow local guidance and discard questionable eggs.
The Bottom Line
The egg float test is a useful demonstration of how an egg changes as it ages, but it is not a reliable food-safety test.
An egg floats because its internal air cell has grown, making it more buoyant. That means the egg is older—not necessarily rotten.
A sinking egg is not guaranteed safe, and a floating egg is not automatically dangerous.
For better protection, consider the egg’s storage history, shell condition, odor, appearance, and cooking method. Keep eggs refrigerated at 40°F or below, store them in their carton on an interior shelf, and cook them thoroughly.
When you cannot verify how an egg was stored or something seems wrong, the safest decision is to discard it.
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