Does a floating egg mean it’s bad? Here’s what food experts say it really means

With World Egg Day falling on Friday, October 9, 2026, exactly 30 years after the celebration was established in Vienna in 1996, it’s a good moment to revisit one of the oldest kitchen tricks for checking eggs and what it actually tells you. Plenty of people learned this test from their mother or grandmother, but let's look at it again.

Flat, upright or floating?

Put the egg carefully into a bowl or tall glass of cold water.

According to Australian Eggs, an egg that sinks and lies flat on its side is very fresh. If it sinks but stands upright, it is older and should ideally be used soon. If it floats, it is considerably older because its air pocket has expanded.

That makes the test useful when you find several forgotten eggs at the back of the fridge and want an idea of which ones are oldest.

Why older eggs start to float

The physics holds up, but that last conclusion needs a little more explanation. A freshly laid egg has hardly any air pocket. An egg is laid at around 105°F and normally has no air cell at first. As it cools, its contents contract and a pocket of air forms, usually at the wider end between the shell membranes. As the egg ages, moisture and carbon dioxide gradually pass through the porous shell. More air moves in, so that pocket becomes larger. The bigger the air cell becomes, the higher the egg rises. At the same time, the yolk absorbs water from the white, and the white becomes thinner. Eventually the air pocket can become large enough to make the egg buoyant. Refrigeration slows these changes.

A floating egg isn't automatically spoiled

According to the USDA Food Safety and Inspection Service (FSIS), a floating egg is of poorer quality but may still be perfectly safe to use. This water test tells you about the egg's age, not whether harmful bacteria are present. Its advice is to crack an older egg into a separate bowl and check for an unpleasant smell or unusual appearance before deciding whether to use it. A spoiled egg will have a noticeably unpleasant odor, whether raw or cooked.

The reverse is important too: an egg that sinks isn't automatically free of harmful bacteria. Salmonella Enteritidis can contaminate an egg while it is developing inside the hen, before the shell forms.

USDA therefore advises cooking eggs until the white and yolk are firm, particularly for infants, young children, older adults, pregnant women, and people with weakened immune systems. Pasteurized eggs are another option for dishes that call for raw or undercooked egg.

In the US: keep eggs cold

American eggs are generally commercially washed and sanitized during processing. USDA guidance is to buy them refrigerated, take them straight home, and store them in their carton in the coldest part of the refrigerator at 40°F or below, rather than in the refrigerator door. Once refrigerated, they should stay refrigerated.

For best quality, University of Nebraska Extension, citing USDA guidance, says to use purchased eggs within three to five weeks. A sell-by date may pass during that period without automatically making the eggs unsafe.

In the UK: different rules before you buy them

British retail eggs follow a different system. Current UK guidance prohibits washing or cleaning eggs because that can damage the shell's protective cuticle. Eggs are therefore commonly sold without refrigeration, partly to avoid temperature swings and condensation before they reach consumers.

Once home, keeping eggs cool and at a steady temperature remains sensible; UK public-health guidance commonly recommends the refrigerator, preferably in the main compartment rather than the warmer door.

Dutch guidance: box, fridge and point down

Voedingscentrum recommends keeping raw eggs in their carton in the refrigerator at 4°C. The box helps prevent them drying out, while refrigeration slows bacterial growth. It also advises storing eggs with the pointed end downward so the air chamber at the blunt end remains undisturbed, and keeping them away from strongly smelling foods.

Its storage guide gives raw eggs around four weeks in the refrigerator, while advising consumers to follow the date and instructions on an unopened pack.

In short, your grandma's glass-of-water trick still has a use. Just treat it as an age test, not a food-safety verdict: flat means fresher, upright means slightly old, and floating means old, but the next step is to check the egg properly rather than trusting the glass alone.