How Do I Know If Eggs Are Still Good? The Float Test, Honestly Explained

The float test measures an egg's age, not its safety. A fresh egg sinks flat; an older one stands up; a floating egg is old — but it may still be fine. Crack it into a bowl and smell it: a bad egg smells sulfurous and unmistakable.

How to do the float test

Fill a bowl with cold water, deep enough to cover the egg. Use a bowl, not a glass — you need room to see the angle the egg takes.
Lower the egg in gently. Dropping it can crack the shell, and a cracked egg is a different problem: discard cracked eggs, do not test them.
Watch what it does in the first few seconds. The position it settles into is the reading — an egg that sinks flat is fresh, one that stands on end is older, one that floats is old.
Test one egg at a time. Eggs from the same carton can be different ages, so a single float does not speak for the whole dozen.

What each position actually means

What the egg does	What it means	What to do
Sinks and lies flat	Fresh, small air cell	Use it — best for poaching and soft-boiling
Sinks but stands upright	Older, air cell has grown	Still fine — use soon, great for hard-boiling (easier to peel)
Floats at the surface	Old, large air cell	Do not trust the water — crack it into a bowl and smell it before deciding

Why it works: an eggshell has thousands of tiny pores. As an egg ages it loses moisture through them and air takes its place, enlarging the air cell at the blunt end. The bigger the air cell, the more buoyant the egg. The test is physics, not a bacteria detector.

The smell test is the real safety check

Crack a suspect egg into a separate bowl, never straight into your recipe. One bad egg can ruin a whole bowl of batter, and you want to see and smell it on its own first.
A spoiled egg smells sulfurous and unmistakable, raw or cooked. If the smell hits you when you crack it, throw it out. No debate, no second opinion.
Look before you use it. A pink or iridescent egg white is a sign of bacterial spoilage — discard it. A runny white or flat yolk is just age, not danger.
Remember what the float test cannot do. A sinking egg is not proven safe — Salmonella can be present in a fresh, clean-looking egg with no smell and no warning. That is why the USDA advises cooking eggs until the white and yolk are firm, especially for children, pregnant people, older adults, and anyone with a weakened immune system.
Trust the calendar first. Shell eggs keep 3 to 5 weeks in the fridge at 40°F or below. An egg well past that window does not need a water test — it needs the bin.

Catch it before it turns

Eggs are the fridge's quietest expiry: they last so long that nobody tracks them, and the float test only helps once they are already old. FridgeSpy logs eggs the moment you scan the carton or your receipt, estimates their 3-to-5-week window from the pack date, and flags them as use-soon while they are still at their best — so the dozen gets used for frittata or baking instead of ending up in a bowl of water on day 35. Scan the carton when it hits the fridge, and let the nudge, not the float, decide.

Frequently asked questions

Does a floating egg mean it is bad?

Not necessarily. A floating egg is old — its air cell has grown large enough to make it buoyant — but the USDA says it may still be safe to use. Crack it into a separate bowl and check for an off smell or unusual appearance before deciding; if it smells sulfurous, throw it out.

Can you eat an egg that sinks in water?

Probably, but sinking only proves freshness, not safety. Even a fresh egg can carry Salmonella with no smell and no visible sign, so cook eggs until the white and yolk are firm rather than relying on the float test alone.

How long do eggs last in the fridge?

Shell eggs keep 3 to 5 weeks refrigerated at 40°F or below, counted from purchase. Hard-boiled eggs last 1 week, and raw eggs out of the shell last 2 to 4 days.

Is the float test reliable?

For age, roughly — it tracks the growing air cell well enough to sort fresh from old. For safety, no: it cannot detect bacteria, and the UK Food Standards Agency says the same — the float test measures age, not whether an egg is safe to eat. Use the pack date, the smell test, and proper cooking instead.

Sources: USDA Food Safety and Inspection Service (egg float test and air cell, crack-and-smell guidance, 3–5 week shell egg storage, cook eggs until firm); FDA FoodKeeper (refrigerator storage times for shell eggs); UK Food Standards Agency (float test measures age, not safety).