The date stamped on an egg carton is often a sell-by date, not an expiration date. Eggs can remain perfectly good for three to five weeks past purchase if stored properly in the refrigerator. But sometimes the carton has been thrown away, or you’re not sure how long they’ve been sitting there. These are the tests worth knowing.
The float test
Fill a bowl or tall glass with cold water and gently lower the egg in. A fresh egg sinks and lies flat on its side. A week-old egg sinks but tilts slightly, with the wide end angled upward. An egg that floats entirely should be discarded.
This works because eggshells are porous. As an egg ages, moisture and carbon dioxide escape through the shell and air seeps in, expanding the air cell at the wide end. The older the egg, the more air inside — and the more buoyant it becomes. A floating egg isn’t necessarily rotten, but it’s old enough that the risk isn’t worth it. The float test tells you about age, not about contamination.
The smell test
If the float test leaves you uncertain, crack the egg into a small bowl and smell it before adding it to anything. A bad egg produces hydrogen sulfide as bacteria break down the proteins inside — the smell is unmistakable, the kind of sulphur note that registers immediately and leaves no room for doubt. If there’s any off smell at all, throw it out. Your nose is the most reliable instrument in the kitchen for this particular job.
The visual check
When you crack a fresh egg onto a flat surface, the yolk sits high and rounded, and the white has two distinct layers — a thick gel-like portion close to the yolk and a thinner watery ring around it. An old egg spreads flat: the yolk is low and breaks easily, and the white is mostly thin and runny. The egg may still be edible at this stage — it’s just past its prime for dishes where texture matters, like fried or poached eggs. For baking or scrambled eggs, it’s usually fine.
A note on the dates
In the US, cartons show a sell-by date or a Julian date (the numbered day of the year, 1–365, printed near the sell-by). Either way: refrigerated eggs are typically good for four to five weeks from the pack date. The USDA allows a sell-by date up to 30 days after packing. So an egg carton bought the day before its sell-by date can still have weeks of life in it.
The practical rule: use the float test when in doubt, crack into a separate bowl before combining with other ingredients, and trust your nose. If all three checks pass — sinks, smells clean, white is intact — the egg is good.
