How to Know if Eggs Are Spoiled: A Simple Guide to Freshness

November 14, 2025 •

4 min read

According to the U.S. Department of Agriculture (USDA), properly stored fresh eggs can last for several weeks beyond the pack date. However, to ensure safety and quality, it is crucial to know if eggs are spoiled before consumption.

Quick Summary

Learn reliable methods to check egg freshness, including the water float test, the sniff test, and visual inspection. Understand the difference between an old and a rotten egg, and get tips for proper storage to extend shelf life.

Key Points

Use Multiple Senses: Combine the float test, visual inspection, and the sniff test for the most accurate assessment of an egg's quality.
Float Test Indicates Age: A floating egg is old and should be discarded, while a fresh one will sink and lay flat.
Sniff Test is Best for Spoilage: A foul, sulfurous odor is the clearest and most reliable sign of a rotten egg.
Look for Discoloration: Cracking an egg reveals important visual cues; discard if the white is pink, green, or iridescent.
Store Eggs Properly: Keep eggs in their original carton on a cold shelf inside the refrigerator to extend freshness and prevent spoilage.
When in Doubt, Throw it Out: If any test gives you pause, it's safer to discard the egg than risk foodborne illness from bacteria like Salmonella.

Your Guide to Egg Freshness

Determining whether an egg is safe to eat involves more than just checking the expiration date on the carton. An egg's freshness is a function of time and storage conditions, and it is possible for a perfectly good egg to be past its 'best-by' date, and vice versa. Knowing how to test your eggs can prevent food waste and ensure kitchen safety. Several straightforward methods can be used to check an egg's quality, even without cracking it open.

The Float Test: A Visual Indicator of Age

One of the most popular and easiest methods is the float test. This relies on a simple principle: as an egg ages, its shell becomes more porous, allowing more air to enter and create a larger air cell at the wide end.

To perform the test:

Fill a bowl or a tall glass with enough cold water to fully submerge an egg.
Gently place the egg in the water.
Observe its behavior and use the following guidelines:
- Very Fresh: The egg sinks to the bottom and lies flat on its side.
- A Few Weeks Old: The egg sinks but stands upright on one end, indicating the air cell has grown. It's still safe to eat.
- Old or Spoiled: The egg floats to the surface. It should be discarded.

The Sniff Test: The Most Reliable Method

While the float test is a good gauge of age, the most accurate way to detect a truly spoiled egg is by using your nose.

How to conduct the sniff test:

Crack the egg into a small bowl, not directly into your food.
Take a sniff. A fresh egg should have little to no odor.
If the egg emits a foul, rotten, or sulfurous smell, it is bad and must be discarded.

Visual Inspection: Look for Red Flags

After cracking the egg, a visual check provides further confirmation of its condition. Look for both subtle and obvious signs of spoilage.

What to look for after cracking the egg:

Yolk: A fresh egg will have a firm, round, and high-standing yolk. As it ages, the yolk flattens and may break more easily.
Egg White (Albumen): The albumen of a fresh egg is thick and slightly cloudy, holding its shape well around the yolk. An older egg's white will be more watery and spread out.
Discoloration: Pink, green, or iridescent tints in the egg white are a clear sign of bacterial contamination. Likewise, black or green spots can indicate a fungal or bacterial infection.

The Shake Test: An Unreliable Anecdotal Method

Some suggest that shaking an egg near your ear to listen for a sloshing sound is a way to test for freshness. The theory is that a sloshing sound indicates a watery, older egg. However, this is not a scientifically endorsed test and is far less reliable than the float or sniff tests. It is not recommended as a primary method for checking egg quality.

Comparison of Egg Freshness Tests


Test	How it Works	Indicates	Reliability	Safety	Best For
Float Test	Measures the size of the air cell, which expands with age.	Age, not necessarily spoilage.	High for freshness, moderate for spoilage.	Safe (no cracking involved).	Quick, non-invasive check for age.
Sniff Test	Detects the sulfurous odor of a spoiled egg.	Spoilage due to bacteria.	High; the most accurate sign of spoilage.	Safe (if cracked into separate bowl).	Absolute confirmation of a rotten egg.
Visual Inspection	Assesses yolk firmness, albumen consistency, and discoloration.	Age and bacterial contamination.	High; provides clear evidence of contamination.	Safe (if cracked into separate bowl).	Final check after opening, especially for discoloration.
Shake Test	Listens for sloshing sounds inside the shell.	Age (watery whites), but not safety.	Low; unreliable and not scientifically backed.	Safe (no cracking involved).	Not recommended as a definitive test.

Best Practices for Egg Storage

To minimize the risk of spoilage and extend the life of your eggs, proper storage is key. The United States Food and Drug Administration (FDA) recommends keeping eggs refrigerated at 40°F (4°C) or colder.

Use the original carton: Store eggs in their original carton on a middle or back shelf of the refrigerator. The carton protects them from absorbing strong odors and flavors from other foods through their porous shells.
Avoid the refrigerator door: The temperature on the refrigerator door fluctuates the most, which can accelerate the aging process. The constant temperature of the main shelves is better for long-term storage.
Don't wash eggs: Commercial eggs are already washed and coated with a protective layer before packaging. Washing them at home can remove this layer and make the shell more susceptible to bacterial entry.
Refrigerate promptly: Don't leave refrigerated eggs out for more than two hours. A cold egg can sweat at room temperature, which can facilitate the growth of bacteria.

Conclusion

In summary, while sell-by dates provide a general guideline, they are not the ultimate measure of an egg's safety. Relying on your senses—primarily smell and sight—is the most dependable strategy to know if eggs are spoiled. The float test is a great initial step to gauge freshness, but the sniff test provides the most accurate and crucial determination of a rotten egg. By combining these methods with proper storage, you can confidently use your eggs and reduce food waste. When in doubt, it is always safest to throw it out to avoid foodborne illness.

For more detailed information on egg safety and storage, the U.S. Food and Drug Administration offers comprehensive guidelines.

Frequently Asked Questions

A bad egg will have a very strong, unpleasant, sulfurous, or rotten odor. This smell is the most reliable indicator that an egg is spoiled.

Not necessarily. A floating egg is old, as its air cell has expanded, but it may still be safe to eat. You should crack it open into a separate bowl to perform the sniff test and check for any foul odors or discoloration to be certain.

If properly refrigerated at 40°F or below, whole, uncracked eggs can often last for several weeks after the 'sell-by' or 'expiration' date printed on the carton. The best guide is to use a freshness test rather than relying solely on the date.

A watery or runny egg white indicates that the egg is older. As eggs age, the protein in the whites thins out, causing them to spread more easily when cracked. This doesn't mean it's spoiled, but it is past its peak freshness.

Yes, an egg with a blood or meat spot is safe to eat. These spots are caused by a ruptured blood vessel during the egg's formation and are not an indication of spoilage or fertilization.

It is better to store eggs in their original carton on a colder shelf inside the refrigerator rather than the door. The door's temperature is less consistent and more prone to fluctuation, which can shorten the eggs' shelf life.

Yes, consuming a spoiled egg contaminated with bacteria like Salmonella can lead to foodborne illness. Symptoms can include diarrhea, fever, and stomach cramps. Always use the sniff test to ensure an egg is safe before consumption.