Kitchen question, straight answer

The Egg Float Test — Myth or Not?

You have probably heard it: drop an egg in water. If it sinks, it is good. If it floats, throw it out. Here is what that test can really tell you — and what it cannot.

The honest verdict

The float test measures an egg’s age — not its safety.

The UK Food Standards Agency says it does not advise using the float test. The reason is simple: the test shows how old an egg is. It says nothing about which bacteria might be inside it.

Illustration of a glass bowl of water with three eggs — one sunk flat on the bottom, one tilted up, and one floating — next to an open carton of eggs. — One bowl, three eggs, three ages. The water can sort eggs by age. It cannot sort them by safety.

Try the test

Pick an egg and watch what the water does. Each result tells you one thing only: roughly how old the egg is.

Lies flat on the bottom. The air pocket inside is still tiny, so the egg is heavy for its size. This egg is the freshest of the three.

Every result above is about age. None of them says a word about germs.

Why old eggs float

An eggshell is not sealed tight. It has thousands of tiny holes in it. As an egg sits, moisture slowly escapes through those holes, and air slowly gets in.

That air gathers in a pocket at the wide end of the egg, called the air cell. The older the egg, the bigger the pocket grows. A small pocket and the egg sinks and lies flat. A bigger pocket tips the egg up on its end. A big enough pocket and the egg floats, like a tiny boat.

So floating says one word: older. Nothing more.

The test can fool you both ways

Floats — but may be fine

A floating egg is not always a bad egg

An old egg can still be safe to eat. The USDA notes that floating eggs may be poorer quality — thinner whites, less flavor — without being unsafe. Floating alone is not proof an egg has gone bad.

Sinks — but may not be safe

A sinking egg is not a promise

Salmonella, the germ that makes eggs risky, does not change how an egg floats at all. A fresh egg that sinks flat can still carry it. The water cannot see bacteria, and neither can this test.

What actually works

Skip the water trick and use these three checks instead. They come straight from USDA egg safety guidance.

Watch the date, and store eggs right

Kept in the fridge, eggs stay good for 3 to 5 weeks from the day you buy them. Keep them in their carton, in the main part of the fridge at 40°F or below — not in the door, where the temperature swings every time it opens.
Crack each egg into a bowl by itself first

Before an egg goes into anything else, crack it alone into a small bowl and look and sniff. A rotten egg gives itself away: a strong sulfur smell, and a white that looks pink, green, or black. If you see or smell that, the egg goes straight in the trash — and wash the bowl before using it again.
When in doubt, throw it out

No sniff test and no float test can prove an egg is safe. If something seems off and you are not sure, let it go. One egg is not worth a case of food poisoning.

One good use for older eggs

Old-but-sound eggs are the best choice for hard-boiling. As an egg ages, the chemistry of the white changes, and the shell peels away cleanly instead of tearing the egg apart. So save your oldest good eggs for the pot — just check each one with the bowl-and-sniff test above before you cook it.

The bottom line

The float test is not fake, and it is not magic. It does one small job — guessing an egg’s age — and it gets trusted for a bigger job, judging safety, that it simply cannot do. For safety, trust the date, the fridge, and your own nose.

Sources: USDA egg storage and safety guidance (refrigerated eggs keep 3–5 weeks; store at 40°F or below; floating eggs may be poorer quality without being unsafe; older eggs peel more easily hard-boiled). UK Food Standards Agency, head of foodborne disease, on the float test (shows age, not bacteria; not advised as a safety test).

About this page: Official guidance in plain words, for general information. Checked November 2026.