Four checks you can run in under a minute reveal whether an egg is still safe to eat: read the carton date, eyeball the shell, drop the egg in cold water, and crack it into a bowl to sniff. A fresh egg sinks, lies flat, and smells almost neutral, while a spoiled one smells unmistakably sulfurous the instant the shell breaks.
Toss any egg with an off odor, a pink or green tint in the white, or a shell dusted with powdery residue, and you’ll sidestep most of the foodborne risk tied to eggs at home.
This guide walks you through the decision order home cooks actually use, from printed date to final sniff, and explains why properly refrigerated eggs often outlive their labels by weeks. You’ll see what the float test really measures, when Salmonella becomes the bigger worry, and the storage habits that quietly add seven to ten extra days to every dozen you buy.
Why Eggs Go Bad in the First Place
A raw egg sits inside a shell that breathes. Tiny pores let moisture and carbon dioxide escape while ambient air seeps in, and the air cell tucked at the wider end grows a little larger every week. That slow exchange is why a freshly laid egg looks tight and perky while a four-week-old one feels lighter and sounds faintly hollow when tapped. Aging itself is harmless.
The danger comes from bacteria that exploit the same pores, especially Salmonella, which can move inward if the shell cracks, gets washed poorly, or sits in warm, dirty conditions.
Temperature swings make everything worse. Pulling eggs from the fridge into a 70°F kitchen for twenty minutes and back again lets condensation form on the shell, and that moisture film can carry surface bacteria into the pores. The Food and Drug Administration recommends keeping eggs at or below 40°F (4°C) from the moment they leave the store until you crack them, because every hour above that line shortens the safe window.
A steady, cold egg resists spoilage for roughly five weeks past its sell-by date; a warm one may turn in half that time.
What the Dates on an Egg Carton Actually Mean
Egg cartons carry at least one printed code, often three, and only one of them is a real safety cutoff. The rest are quality nudges, not deadlines, which is why so many home cooks throw away perfectly good eggs while others push their luck past a safe point.
| Date Type | What It Means | Who’s Responsible | Treat It As |
|---|---|---|---|
| Sell-By | Last day a store should keep it for sale | Retailer guideline | Quality marker; eggs are usually fine 3–5 weeks past it when refrigerated at or below 40°F |
| Use-By / Best By | Peak quality window | USDA recommendation | Quality, not safety; ignore if the egg passes your tests |
| Expiration | Hard cutoff in a few states (notably California) | State regulation | Hard limit where enforced; safe buffer still exists for properly stored eggs |
| Pack Date / Julian Date | Day eggs were washed and packed (001 = Jan 1) | USDA rule since 2000 | Adds 28–35 days for a realistic freshness window |
If the only date on your carton is a Sell-By stamped five weeks ago, don’t toss the eggs yet. Run the float test, crack one into a bowl, and sniff. The American Egg Board notes that properly refrigerated eggs rarely spoil within four weeks of purchase, and many last a full week longer.
The bigger danger is the egg with no date at all, the one from a dented corner of the cooler, or the one forgotten in the back of the fridge since last month’s grocery run.
Even with a reliable date, an egg that has sat neglected deserves a closer look before it reaches the pan.
When in doubt, throw it out. The dollar you save on one egg isn’t worth a day spent in the bathroom.
Inspecting the Shell Before You Crack Anything
The shell tells the truth about half the eggs you should never crack in the first place. Hold it up to the light and look for hairline cracks, a chalky or dusty film, or any patch of pink, green, or black discoloration. A powdery bloom is normal on unwashed farm eggs, but a dusty film on a store-bought egg often signals mold growth, especially after a humidity spike in the fridge.
Visible Red Flags You Should Never Ignore
- Hairline cracks: bacteria slip through even invisible fractures within minutes
- Powdery white or pink residue: surface mold that may have grown inward
- Unusual dark spots on the shell: bacterial colonies forming before the egg ever cracked
- Leaking through the carton: past-prime eggs release moisture that pools in the cardboard
Visual checks catch the obvious cases but miss the invisible ones. Salmonella contamination leaves no trace on the shell, in the white, or in the yolk, and an egg can look perfect and still harbor enough bacteria to cause foodborne illness. Treat shell inspection as a quick filter, then trust your nose to finish the job once the egg is open.
The Float Test and What It Really Tells You
The water glass is the most reliable at-home freshness test, and it works on simple physics. Fill a tall glass or measuring pitcher with cold water, lower the egg in gently, and watch how it settles. A new egg sinks and lies flat on its side. An older egg tilts upward, then stands on its small point.
A very old egg floats near the surface because the air cell inside has grown large enough to make the whole egg buoyant.
Reading the Results
- Sinks and rests flat: very fresh, often less than a week old, best for frying and soft boiling
- Sinks but tilts upward: two to three weeks old, still fine for almost any use
- Stands on end: three to four weeks old, cook thoroughly before eating
- Floats at the surface: very old, often spoiled, but float alone isn’t proof of danger
The test measures age, not contamination. A floating egg has lost moisture and carbon dioxide through its shell over time, and the gas buildup is what carries it upward. Guidance from the American Egg Board and USDA both treats floating eggs as a strong signal to discard, yet a floating one can occasionally be safe, just very dry. Use the float test as a fast first pass, then move to the bowl for the final word.
The Crack-and-Sniff Method as Your Final Check
Crack each egg into a small bowl before it goes into the pan, and never directly into a hot skillet or a recipe that hides the flavor. A fresh egg has almost no smell, just a faint grassy note if anything. The white should be slightly thick and stay close to the yolk, and the yolk should sit round with a clear bull’s-eye on top.
Warning Signs Inside the Shell
- Strong sulfur or rotten smell: bacterial action has broken down the contents, discard the egg
- Pink, iridescent, or greenish white: Pseudomonas or other spoilage bacteria growing in the albumen
- Black or dark red spots in the yolk or white: blood spots are usually harmless, but dark mottling suggests spoilage
- Runny, watery white that spreads wide: albumen thinning from age, safe but past prime for poaching
Watch the dishes where one bad egg can hide behind flavoring. Homemade mayonnaise, hollandaise, custards, ice cream bases, and Caesar dressing all depend on raw or barely cooked eggs, and a sulfurous note vanishes under mustard, vinegar, or vanilla. Crack every egg into a separate bowl first, smell each one, then combine. For baked goods, a single spoiled egg can ruin a whole cake because the off-flavor bakes in rather than cooks out.
Catching a bad egg before it joins the batter matters most when baking, where off-flavors spread through everything rather than dissipating.
Storage Habits That Keep Eggs Fresh Longer
Where the egg sits in your fridge matters more than most people realize. The door is the warmest spot because it opens and closes all day, and the temperature there swings by several degrees every time you reach for the milk. Move the carton to the middle shelf, toward the back, where the air stays coldest and steadiest, between 35°F and 40°F.
A dedicated egg tray on the middle shelf keeps them grouped and easy to count, and it removes the temptation to leave them out on the counter after cracking.
Smarter Storage Moves
- Keep eggs in the original carton: the cardboard blocks odor absorption from onions and garlic and protects against moisture loss
- Avoid washing until just before use: washing strips the protective bloom and lets bacteria move through the pores faster
- Don’t freeze eggs in the shell: crack them, beat lightly, and freeze in ice cube trays for up to a year
- Refrigerate promptly after every use: raw eggs left at room temperature for more than two hours enter the danger zone
Hard-cooked eggs last about one week in the fridge, roughly half the shelf life of raw eggs, because boiling removes the bloom and pushes any surface bacteria deeper into the pores. Keep them in a sealed container so they don’t pick up odors from leftovers, and never leave a peeled hard-boiled egg sitting in water for more than a couple of hours.
Raw whites freeze beautifully on their own and thaw in minutes for meringues, while yolks need a pinch of salt or sugar before freezing to keep their texture.
Bottom Line
A reliable sequence beats a memory trick every time. Read the carton date as a quality hint, eyeball the shell for cracks or powder, drop the egg in cold water to gauge age, and finally crack it into a bowl for the sniff test. If anything smells sulfurous, looks discolored, or has a shell that feels wrong, send it to the trash.
Properly refrigerated eggs stay safe well past their printed dates, so the float test plus the sniff test lets you keep every egg that’s still good and discard only the ones that aren’t.
FAQ
How long do eggs stay good after the expiration date?
Refrigerated eggs are often safe for three to five weeks past the Sell-By date when kept at or below 40°F. Treat the expiration date as a quality marker, not a safety cutoff, and verify each egg with the float and sniff tests before cooking.
What does a bad egg look like inside?
A spoiled egg typically has a pink, green, or iridescent white, a flattened yolk, and dark spots in either the yolk or albumen. The smell is the giveaway: a sulfurous, rotten odor that hits the moment the egg cracks open.
Do hard-boiled eggs go bad faster than raw eggs?
Yes. Hard-cooked eggs stay safe in the refrigerator for about one week, roughly half the shelf life of raw eggs. Boiling removes the protective bloom on the shell and lets surface bacteria move deeper, which shortens the safe window.
Can you eat an egg that floats in water?
Floating eggs are very old and should usually be discarded, but float is not proof of contamination. Run the sniff test before deciding. If the egg smells clean and looks normal once cracked, it’s likely safe; if it smells sulfurous, throw it out.
How should eggs be stored to stay fresh longer?
Keep them in the original carton on the middle shelf of the fridge, where the temperature holds steady at or below 40°F. Avoid the door, which warms up each time it opens, and skip washing until just before you crack them.
