How to Tell if an Egg Is Bad: Reliable Signs and the Float Test

You drop an egg into a glass of water and it floats. The internet’s usual verdict is immediate: “bad egg.” But the test does not actually tell you that. Floating mainly tells you the egg is older, because its air cell has grown; it is not a safety test.

The clearest household sign of genuine spoilage usually appears after cracking the egg: a strong, unpleasant odor. Freshness, spoilage, and microbiological safety are different questions. An egg can lose cooking quality without being rotten, while a normal-looking egg is not automatically proven free of pathogens.

What the main signs actually mean

The point of the table is to separate clues that answer different questions. “Old,” “less fresh,” and “spoiled” are not synonyms. Knowing how the egg was stored and whether its shell remained intact gives you more useful information than any single kitchen trick.

Smell is the most direct spoilage clue

A spoiled egg develops a characteristic unpleasant odor whether raw or cooked. If you are unsure about an older egg, crack it into a small separate bowl before adding it to batter, a skillet, or other eggs.

There is no reason to taste it. A clearly bad smell is enough reason to throw it away. A separate bowl also lets you notice an obviously abnormal appearance before the egg is mixed through an entire dish. That is a simple kitchen habit that prevents one questionable egg from ruining several good ingredients.

What the float test is really measuring

As an egg ages, moisture and gases escape through the shell and the internal air cell grows. That changes buoyancy, which is why older eggs are more likely to stand upright or float.

• Sinks and lies flat: usually fresher.
• Sinks but stands upright: older.
• Floats: has a larger air cell and is older still.

USDA notes that a floating egg can still be usable. The test does not detect Salmonella or other pathogens. The reverse matters too: an egg that sinks is not certified pathogen-free. Think of the water test as a rough age sorter, not a substitute for storage, handling, and cooking guidance.

A runny white usually tells you about age, not rot

Fresh egg whites tend to be thicker and the yolk sits higher. As the egg ages, the white becomes more fluid and spreads farther in a pan.

That can affect cooking quality—for example, how neatly a fried or poached egg holds together—but it is not automatically a sign of dangerous spoilage. An older egg with a thin white, intact shell, normal odor, and appropriate storage history may simply be less fresh for a recipe where appearance matters.

Yolk color is not a freshness gauge

A deep orange yolk does not prove the egg is fresher, and a pale yolk is not a spoilage sign. Color depends mainly on pigments in the hen’s diet.

Two cartons can therefore produce very different yolk colors even when the eggs are similar in age. Using color as a date code can lead you in the wrong direction. Package dating, shell condition, and storage history are much better clues when you are deciding how old an egg may be.

Blood spots are usually less dramatic than they look

A small blood spot can result from a tiny ruptured vessel during egg formation. It does not mean the egg is fertilized or rotten and can be removed for appearance if desired.

The useful distinction is between one small localized spot and broader abnormal changes in the contents. Not every unfamiliar detail is spoilage. If unusual color, odor, and texture occur together, that is a different situation from a single blood spot in an otherwise normal egg.

The shell deserves more attention

An intact shell is a protective barrier. An egg that has been cracked and leaking for an unknown amount of time creates more opportunity for contamination than one you crack immediately before cooking.

If a shell was already damaged in the carton, the unknown time since the crack matters. Do not treat a leaking egg that has been sitting that way as equivalent to one you accidentally crack into a clean bowl just before cooking. Shell condition is one of the few clues you can evaluate before opening the egg.

Can a normal-smelling egg contain Salmonella?

Yes. Pathogens do not have to produce a detectable odor. Storage, handling, and cooking still matter even when the egg looks and smells normal.

This is why the sniff test cannot be used as permission to ignore poor temperature control. Smell is useful for identifying obvious spoilage, not for proving microbiological safety. The intended preparation also matters: a thoroughly cooked egg presents a different situation from one used raw or lightly cooked.

Refrigerator storage in the U.S.

USDA recommends refrigerating shell eggs and lists a typical refrigerator storage time of 3–5 weeks from purchase. Hard-cooked eggs keep about 1 week.

Those storage times assume the refrigerator stays cold and the eggs are handled normally. If an egg spent extended time warm or the shell was damaged, the calendar alone does not erase that history. Dating the carton and keeping eggs consistently refrigerated makes age much easier to judge than relying on a float test later.

A simple way to check an egg you are unsure about

1. Check that the shell is intact.
2. Crack the egg into a separate small bowl.
3. Look for a clearly abnormal appearance.
4. If there is a strong off odor, discard it.
5. If it appears normal, use it within appropriate storage and cooking practices.

You do not need to float every egg. When you know the purchase date and the eggs have stayed refrigerated, cracking a questionable one separately usually gives you more useful cooking information than an indirect buoyancy test.

What is worth remembering

Smell after cracking is a spoilage clue; floating is an age clue. An older floating egg may still be usable, and a sinking egg is not guaranteed safe. A thin white, pale yolk, or small blood spot is also not an automatic discard signal.

The best decision combines shell condition, storage history, date, appearance after cracking, and odor. That keeps a popular kitchen test in its proper place: helpful for estimating age, but not powerful enough to certify safety.

Sources

• USDA FSIS — Shell Eggs from Farm to Table — Egg freshness, float test and handling.
• FoodSafety.gov — Cold Storage Chart — Refrigerator storage times.