Four at-home checks you can finish in under a minute,reading the date, doing the float test in cold water, inspecting the shell, and cracking one open to judge the yolk, white, and smell,sort fresh eggs from suspect ones fast. A fresh egg sinks and lies flat in water, has a thick white, a rounded yolk, and no off-odor, while a bad egg floats, smells sulfurous, or shows pink, green, or black discoloration.
This guide covers every check you can run with a glass of water and your own nose, plus the storage habits that keep a carton fresh for weeks past the printed date.
What the Dates on an Egg Carton Actually Mean
Sell-by, best-by, use-by, and expiration are four different stamps that the USDA does not regulate uniformly, and that gap confuses nearly everyone staring at a Sunday-morning carton. Only the sell-by date falls under federal grading rules for shell eggs, and even then it tells the retailer when to pull stock from the shelf, not when the egg inside stops being safe to eat.
Manufacturer guidelines govern the other three labels. Best-by and use-by mark the date the producer expects peak quality in flavor, texture, and baking performance. Expiration appears on some cartons, often as a calculated date roughly 30 days after the eggs were packed, but it carries no extra legal weight. None of these dates is an automatic safety deadline once the carton sits in a fridge at or below 45°F.
How Long Eggs Stay Fresh Past the Printed Date
The USDA recommends using eggs within 3–5 weeks of purchase when kept refrigerated, and that window starts from the packing date, not the date stamped on the lid. A carton bought today with a sell-by date three weeks out can still produce a perfectly good egg five weeks from now, because cold storage slows the moisture and carbon dioxide loss that drive aging.
Storage temperature swings that line matters more than the printed number. An egg bouncing from 40°F to 65°F and down again ages the air cell faster than one held steady at 38°F, which is why a date label is a quality hint rather than a hard deadline.
| Date Label | What It Means | Who Sets It |
|---|---|---|
| Sell-by | Last day a retailer should sell the carton | USDA (for graded eggs) |
| Best-by / Use-by | Peak quality, not a safety cutoff | The egg producer |
| Expiration | Often ~30 days after pack date; no added legal status | State law or producer |
| Pack date (Julian) | Day of the year eggs were graded and packed | The egg producer |
The Float Test and the Science Behind Why It Works
Fill a tall glass with cold water, lower an egg in gently with a spoon, and watch how it settles. The result tells you roughly how old the egg is, because every shell is a porous membrane that loses moisture and carbon dioxide over time, enlarging the air cell at the wide end and slowly lowering the egg’s average density.
Decoding the Three Results
A fresh egg, usually less than two weeks old, sinks and lies flat on its side at the bottom. An egg a few weeks older tilts upward, balancing on the small end with the large end angled toward the surface.
An egg that floats at the top is old, with an air cell large enough to make the whole egg buoyant, and the American Egg Board recommends cracking it into a separate dish before use even if you decide to cook it.
Because older eggs tend to have thinner whites and flatter yolks once cracked, the float test is a screening step, not the final verdict. A floating egg may still cook fine; a sunken one is almost always safe.
Why the Egg Actually Floats
Eggshells contain thousands of microscopic pores. As water evaporates and CO2 escapes through those pores, the air pocket at the wider end grows from a pinpoint at lay to a coin-sized bubble after several weeks, reducing average density below that of water. That shift from sinking to tilting to floating is the entire physics behind the test, and it is why refrigerated eggs age more slowly than room-temperature ones.
If the float test feels too hands-off, opening an egg gives you immediate, unmistakable information about its condition.
Tip: run the float test on a suspect egg before cracking. Cold water keeps the temperature stable and the read cleaner than tap water straight from a hot pipe.
Cracking an Egg Open: Reading the Yolk, White, and Smell
Crack the egg onto a white plate or into a small bowl, not directly over a pan you cannot undo. The first cue is the white, then the yolk, then the smell, in that order, because the nose catches problems the eye can miss.
Cues That Say Fresh
A fresh egg white sits thick and gel-like, holding its shape in two distinct layers around the yolk, with a small inner ring that barely spreads. The yolk domes upward, almost like a half-sphere, and the surface looks smooth and brightly colored. There is no off-odor at all, just a faint clean smell.
Cues That Say Old but Still Edible
Older eggs crack open with whites that run thin and spread wide across the surface, and the yolk often appears wider, flatter, and more easily broken. That spread does not automatically mean spoiled. The egg is past its peak for poaching or frying where presentation matters, but it scrambles, bakes, and hard-boils fine because heat sets the protein regardless of how thin the white looked in the pan.
Cues That Mean Discard
- Sulfur or rotten smell: A clear, unmistakable stink the moment the shell breaks.
- Pink, iridescent, or greenish whites: Bacterial growth, often Pseudomonas.
- Black or green spots: Mold starting somewhere on the yolk or white.
- Sour or unusually sharp odor: Spoilage even if the color still looks fine.
If any of these cues show, send the egg to the trash and wash the plate in hot, soapy water before cracking the next one. Salmonella contamination is the other reason an egg can still be dangerous without showing any of these cues, which is why cooking to a firm yolk-and-white is the final safety layer, not smell alone.
Shell Inspection and the Look-and-List Rule for Whole Eggs
Before you crack anything, read the shell. The shell is the egg’s first defense, and most spoilage starts with a flaw you can see in your hand, not a smell you have to hunt for.
What to Check on the Outside
Look for cracks, hairline fractures, or tiny punctures that let bacteria slip past the shell. Run a thumb lightly across the surface. A normal shell feels slightly rough and chalky; a slimy or powdery feel is suspect. Watch for unusual discoloration, green or gray patches, dark stains, or a faint musty smell coming through the shell, all signs that the egg has been sitting in conditions that favor bacterial growth.
Eggs at the store should sit in the refrigerated case, not on a warm end-cap display. If a shell feels cold, that is a good sign. If it feels room-temperature, the cold chain has been broken somewhere.
Candling With a Flashlight at Home
Candling, holding an egg over a bright light to reveal its interior, is the method USDA graders use on every commercial egg. At home, a strong LED flashlight held right against the shell in a dark room does the same job. A fresh egg looks mostly opaque with a faint shadow of the yolk. An older egg shows a clearly visible air cell at the wide end. Dark spots, blood rings, or moving shadows are reasons to toss the egg.
Blood Spots Versus Spoilage
A small red or brown speck on the yolk is a blood spot, a ruptured vessel during formation, and is harmless. It does not mean the egg is contaminated and it does not affect flavor. Discarding that egg is purely a choice about appearance. Dark spots that grow as the egg ages, especially with any off-odor, point to spoilage rather than a benign blood spot.
Catching problems at the shell stage keeps spoilage from spreading into your storage habits and your breakfast.
Storage Habits That Stretch Freshness and the Salmonella Question
Storage habits decide whether a carton lasts three weeks or five, and they also decide the Salmonella risk that scares people off raw cookie dough and runny yolks.
Where and How to Keep Eggs Cold
Store eggs in the original carton on a middle or lower shelf where the temperature stays steady, not in the door where every opening sends the eggs through a mini temperature swing. Keep the fridge at or below 45°F, the upper end of the USDA recommendation, and ideally closer to 35–40°F for the slowest aging. The carton matters because it blocks odor transfer from other foods and protects the shells from light and humidity loss.
Why US Eggs Need Refrigeration and European Eggs Often Do Not
US producers wash eggs to remove the cuticle, the natural protein coating that keeps bacteria out of the shell, because USDA grading rules require a clean surface. That wash also strips the protective layer, which forces cold storage. Many EU producers skip the wash and vaccinate their flocks against Salmonella enteritidis, which is why unrefrigerated eggs sit on European shelves for weeks without spoiling.
The difference comes down to food safety philosophy. Either approach keeps the bacterial risk low when practiced correctly, and the FDA, the American Egg Board, and the Egg Safety Center all agree that US eggs must stay refrigerated from packing through cooking.
The Salmonella Reality
An egg contaminated with Salmonella can look, smell, and feel perfectly normal. Roughly 1 in 20,000 commercially sold eggs carries the bacteria according to USDA surveys, and you cannot see it, smell it, or float-test it out. Cooking both the yolk and white until firm reaches an internal heat high enough to kill the bacteria, which is the reason soft-boiled and runny-yolk preparations carry a higher (still low, but real) risk than fully set eggs.
Warning: never taste a raw or undercooked batter to check seasoning if it contains eggs. A pinch of cooked test portion from a small skillet is the only safe way to taste as you go.
When an Egg Edges Toward the Trash, and What If You Already Ate One
Pull every signal together into a single decision before you crack or commit. Run the float test first, then crack into a separate dish, then judge the white, yolk, and odor, and finally let the most cautious signal win.
A Quick Keep-or-Toss Decision Tree
- Sinks and lies flat: Keep, very fresh.
- Tilts upward: Keep, still good for cooking and baking.
- Floats but smells fine: Use soon, ideally in a fully cooked dish.
- Floats and smells off: Discard.
- Cracked shell or visible mold: Discard without cracking.
If You Already Ate a Questionable Egg
Symptoms of egg-related foodborne illness usually show up 6 to 48 hours after ingestion and include nausea, vomiting, stomach cramps, diarrhea, and sometimes a low fever. Most healthy adults recover within a day or two without treatment, but dehydration is the real risk, especially for young children, older adults, pregnant people, and anyone with a compromised immune system.
Call a clinician if symptoms last more than 48 hours, if there is blood in the stool, if a high fever develops, or if vomiting prevents keeping liquids down.
The Final Rule When Doubt Is Still There
The float test alone is not enough. Smell and visual inspection catch what density cannot, and any sulfurous odor, a pink or green tint, or a dark spreading spot is a discard no matter what the float test said. When in doubt after running all four checks, throw the egg out. The cost of one wasted is far smaller than the cost of a weekend lost to food poisoning, and a replacement egg is roughly twenty cents away.
FAQ
How can you tell if eggs have gone bad?
Run the float test, then crack the egg into a separate bowl and look at the yolk, white, and smell. A bad egg floats in cold water, smells sulfurous or rotten, or shows pink, green, or black discoloration. A fresh egg sinks, lies flat, has thick whites, a domed yolk, and no off-odor.
Do eggs go bad after the expiration date?
Eggs often stay good for 3–5 weeks past the printed date when refrigerated at or below 45°F in the original container. The date marks peak quality, not a safety deadline, so a properly stored egg past its expiration is usually still safe to cook and eat.
What does a bad egg look like inside?
Crack a suspect egg and the white may run like water while the yolk sits flat, sometimes tinted pink, iridescent, green, or flecked with black. A sulfurous or sour smell confirms spoilage even if the color still looks normal in the bowl.
Is the float test accurate for checking egg freshness?
The float test is a reliable screening tool because the air cell grows as moisture escapes through the shell. A floating egg is old, and a sunken one is fresh, but the test does not detect Salmonella, so cooking both yolk and white until firm is still required for safety.
How long are eggs safe to eat after the sell-by date?
A steady fridge at or below 45°F buys most cartons another 3–5 weeks of safe eating past the printed sell-by date. Always confirm with the float test and a quick crack-and-smell check before cooking any egg that is more than a few weeks past the stamped date.
Can you eat eggs past their expiration date?
Yes, in most cases, when the eggs have been continuously refrigerated at or below 45°F. Check each questionable egg with the float test and a crack-and-sniff before using it, and cook the yolk and white until firm to handle any bacterial risk the visual checks cannot see.
