The quick answer
- Smell it. Crack the egg into a separate bowl. A spoiled egg has a strong sulphur (rotten egg) smell, raw or cooked. If it smells bad, throw it out.
- Look at it. Discard eggs with cracked, slimy or powdery shells, or with pink, green, black or iridescent spots inside.
- Float test for age. Fresh eggs sink. Older eggs stand up. Eggs that float are very old and best thrown away.
How the float test works
Place the egg gently in a bowl of cold water.
| What it does | What it means |
|---|---|
| Sinks and lies flat on its side | Very fresh |
| Sinks but tilts or stands on its end | Older, still fine to eat if it smells normal. Good for hard-boiling, because older eggs peel more easily |
| Floats | Very old. Most advice is to throw it away |
Why it works: an egg shell is porous. Over time, moisture and carbon dioxide escape and air takes their place, so the air cell at the wide end grows and the egg becomes more buoyant.
What it does not tell you: whether the egg carries bacteria such as salmonella. A fresh-looking egg can still be contaminated, and that is why thorough cooking matters. The float test is a test of age, not safety.
The sniff test is the real test
Bacteria that spoil eggs produce hydrogen sulphide, the smell of rotten eggs. It is unmistakable. Crack eggs one at a time into a small bowl before adding them to a mixture, so one bad egg does not ruin a whole batch.
Other signs of a fresh egg once cracked:
- A firm, rounded yolk and thick white that holds its shape.
- Older eggs have a flatter yolk and a runny white that spreads. They are still fine to eat if they smell normal.
Things that look odd but are harmless
- Blood spots on the yolk: a tiny blood vessel burst during laying. Safe; remove with a spoon if you prefer.
- Cloudy white: a sign of a very fresh egg, caused by carbon dioxide that has not yet escaped.
- Green ring around a boiled yolk: a harmless reaction from overcooking. See how to boil eggs to avoid it.
- Stringy white bits (chalazae): the cords that hold the yolk in place. Normal.
How long eggs last
| Eggs | Storage | Keeps for |
|---|---|---|
| Raw, in the shell | Fridge | About 3 to 5 weeks from purchase |
| Raw, in the shell (unwashed, UK and EU style) | Cool room, below about 20°C | Up to the best-before date |
| Raw yolks or whites | Fridge, covered | 2 to 4 days |
| Hard-boiled | Fridge | About 1 week |
| Raw, beaten | Freezer | Up to 1 year for best quality |
| Cooked egg dishes | Fridge | 3 to 4 days |
Never freeze eggs in their shells: they crack. Our fridge storage guide has times for other foods.
What the dates on the box mean
- United States: cartons may show a sell-by or expiration date set by the producer or state, and a pack date shown as a three-digit day-of-year code (001 is 1 January, 365 is 31 December). Properly refrigerated eggs are usually fine for 3 to 5 weeks after purchase.
- UK and EU: eggs carry a best-before date, set at no more than 28 days after laying. It is a quality date. The UK Food Standards Agency says eggs can be eaten after it if they are cooked thoroughly until both yolk and white are solid.
- Elsewhere: follow the date and storage instructions on the pack.
Storing eggs well
- Keep them in their box, on a shelf rather than in the fridge door, where the temperature swings every time it opens.
- Store pointed end down, which keeps the yolk centred and the air cell at the top.
- Do not wash unwashed eggs before storing; it removes the natural protective coating. If an egg is dirty, wipe it just before use.
- Once refrigerated, keep them cold. A cold egg left out sweats, and moisture on the shell helps bacteria pass through.
Cooking eggs safely
The safest eggs are cooked until the yolk and white are firm, or to 71°C (160°F) in dishes. This matters most for pregnant people, babies and young children, older adults and people with weakened immune systems. In the UK, eggs with the British Lion mark are considered safe to eat runny or raw, even for these groups. Elsewhere, use pasteurised eggs for raw-egg recipes such as homemade mayonnaise or tiramisu. Our guide to safe cooking temperatures covers other foods.
Key takeaways
- The sniff test is the real test: a bad egg smells of sulphur.
- The float test shows age: sinkers are fresh, floaters are very old.
- Refrigerated eggs usually keep 3 to 5 weeks; hard-boiled eggs about a week.
- Best-before is a quality date, not a safety date, but cook older eggs thoroughly.