The egg water test is a quick way to check freshness using nothing but a bowl and cold tap water. A fresh egg sinks and lays flat on the bottom. An older egg tilts upward or floats. The whole process takes about 30 seconds per egg.
Why the Test Works
Eggshells are porous, covered in thousands of tiny holes that allow air to pass through. From the moment an egg is laid, moisture slowly escapes through those pores and is replaced by air. This creates and gradually enlarges an air pocket (called the air cell) at the wide end of the egg. A freshly laid egg has a tiny air cell, making it dense enough to sink. Over weeks, the air cell grows larger, making the egg increasingly buoyant. That’s the entire principle behind the float test: the bigger the air cell, the older the egg, and the higher it rides in the water.
How to Do the Test
Fill a bowl or tall glass with cold tap water, deep enough to fully submerge an egg with a couple of inches to spare. Gently lower each egg into the water one at a time. Don’t drop them in, since cracking the shell defeats the purpose. Watch where the egg settles, then remove it promptly. You don’t want eggs sitting in water longer than necessary, as water can push bacteria through those same tiny shell pores.
What Each Position Means
There are three basic positions you’ll see, and each tells you something different about age:
- Sinks and lays flat on its side: This is a very fresh egg. The air cell is small, so the egg is heavy relative to its size. These are ideal for any use, including poaching and frying, where you want the white and yolk to hold their shape.
- Sinks but tilts upward or stands on one end: The egg is older but still perfectly good to eat. It’s typically one to three weeks old when refrigerated. The air cell at the wide end has grown enough to tip the egg upright. These eggs are actually easier to peel after hard boiling, so they’re great for that purpose.
- Floats to the surface: The air cell is large enough to make the egg buoyant. This egg is old and lower in quality, but floating alone doesn’t automatically mean it’s spoiled. More on that below.
Does a Floating Egg Mean It’s Spoiled?
Not necessarily. The USDA is clear on this point: an egg that floats in water has a large air cell, meaning it’s of poor quality, but it may be perfectly safe to use. Floating tells you the egg has lost a lot of moisture over time. It doesn’t confirm bacterial contamination.
To know for sure, crack the egg into a separate bowl before adding it to anything. A spoiled egg produces an unmistakable sulfur smell, sometimes strong enough to detect through the shell before you even crack it. If the egg smells normal after cracking, it’s safe to cook and eat. If you get any hint of that rotten sulfur odor, discard it immediately. There’s no mistaking the smell.
Other Signs of Freshness to Look For
Once you crack an egg open, the visual clues are just as useful as the float test. A fresh egg has a yolk that sits up tall and rounded, surrounded by a thick layer of white that holds its shape on the plate or in the bowl. As eggs age, the proteins in the white break down, causing it to spread thin and watery. The yolk membrane also weakens, so the yolk flattens out instead of standing up in a dome.
If you crack an egg and the yolk breaks the moment it hits the bowl, or the white runs across the surface like water, the egg is well past its prime. It may still be safe to eat if there’s no off smell, but the texture and cooking performance won’t be great. Older eggs like these work fine scrambled or in baked goods where structure doesn’t matter much.
How Long Eggs Last in the Fridge
Refrigerated eggs stay good for three to five weeks from the day you put them in the fridge. That timeline assumes consistent cold storage, not eggs that have been left on the counter for hours and then returned to the fridge repeatedly. Hard-boiled eggs have a much shorter window: about one week in the refrigerator.
If your eggs have a pack date stamped on the carton (a three-digit number representing the day of the year they were packed), you can use that as a more precise reference than the sell-by date. The float test is most useful when you’ve lost track of when you bought the eggs, or when you’re working with farm-fresh eggs that have no date stamp at all.
Tips for Storing Eggs Properly
Store eggs in their original carton on a shelf inside the fridge, not in the door. The door is the warmest spot and experiences the most temperature fluctuation every time you open it. Keeping eggs in the carton also protects them from absorbing strong odors from other foods through their porous shells.
Store eggs with the wide end facing up. The air cell sits at that end, and keeping it on top reduces the chance of bacteria migrating from the air pocket into the yolk. This is the same reason commercial egg cartons are designed with the pointed end facing down.