How to if eggs are bad

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Last updated: April 4, 2026

Quick Answer: To tell if eggs are bad, perform a float test: fresh eggs sink, older eggs stand on end, and spoiled eggs float. Visually inspect for cracks or sliminess, and smell for a sulfurous odor, which indicates spoilage.

Key Facts

A 'float test' is a common method to check egg freshness: eggs that sink are fresh, while those that float are likely spoiled.
The average egg remains fresh for about 3 to 5 weeks when stored properly in the refrigerator.
Spoiled eggs often emit a distinct sulfurous smell, a clear sign of bacterial growth.
Cracked or slimy eggshells can indicate that the egg has been contaminated and may be unsafe to eat.
Consuming spoiled eggs can lead to foodborne illnesses like salmonella poisoning.

Overview

Eggs are a nutritious and versatile food staple found in kitchens worldwide. However, like all perishable foods, they have a limited shelf life. Knowing how to determine if an egg has gone bad is crucial for food safety and to avoid unpleasant culinary experiences or potential health risks. Fortunately, there are several simple and effective methods to check the freshness and safety of eggs before you use them.

Understanding Egg Freshness

When eggs are laid, they have a protective coating called the 'bloom' or 'cuticle' that helps prevent bacteria from entering the shell. As eggs age, this bloom deteriorates, and the air cell within the egg, located at the larger end, gradually increases in size. This change in the air cell is a key indicator of an egg's age and, consequently, its freshness.

Methods to Check for Bad Eggs

1. The Float Test

This is perhaps the most popular and straightforward method. Gently place an egg in a bowl or glass of cold water. Observe how it behaves:

Fresh Egg: A very fresh egg will lie flat on its side at the bottom of the container.
Slightly Older Egg: An egg that is a few weeks old might stand on one end at the bottom of the container. This is still generally safe to eat, but it's less fresh.
Bad Egg: An egg that floats to the surface is likely spoiled. The increased air cell size makes it buoyant. While some sources suggest older but not necessarily spoiled eggs might float slightly, a distinct float is a strong warning sign.

2. The Visual Inspection

Before cracking an egg, examine its shell. Look for:

Cracks: Any visible cracks in the shell can allow bacteria to enter, compromising the egg's safety.
Sliminess or Powdery Residue: If the shell feels unusually slimy or has a powdery coating, it might be a sign of bacterial growth or mold.

3. The Smell Test

This is the most definitive test for spoilage. Once you crack the egg open (preferably into a separate small bowl before adding it to other ingredients), take a whiff. A fresh egg has a neutral odor. If the egg emits a strong, unpleasant, sulfurous smell (like rotten eggs), it is definitely bad and should be discarded immediately. This smell is due to the breakdown of proteins and the release of hydrogen sulfide.

4. The Appearance Test (After Cracking)

Beyond the smell, the appearance of the egg white and yolk can offer clues:

Fresh Egg White: Will be thick and hold its shape around the yolk.
Older Egg White: Will be thinner and spread out more.
Yolk: In a fresh egg, the yolk will be plump and rounded. In an older egg, it might appear flatter.
Discoloration: If the yolk or white has any unusual pink, green, or iridescent colors, it's a sign of bacterial contamination and should be discarded.

Understanding Egg Expiration Dates

Eggs are typically stamped with a 'sell-by' date or a 'best-by' date. The 'sell-by' date indicates how long a store can display the eggs for sale. The 'best-by' date suggests when the eggs will be at their peak quality. However, eggs can often remain safe to eat for several weeks past these dates if stored correctly. The USDA recommends using shell eggs within 3 to 5 weeks of purchase for best quality, and they can be safe for about 4-5 weeks past the packing date if refrigerated continuously.

Proper Egg Storage

To maximize the shelf life and maintain the freshness of eggs, proper storage is essential:

Refrigeration: Always store eggs in their original carton in the coldest part of your refrigerator, typically on a middle or lower shelf, not in the door where temperatures fluctuate.
Carton: Keep eggs in their carton to protect them from absorbing odors from other foods and to prevent them from drying out.

When in Doubt, Throw it Out

Food safety is paramount. If you have any doubts about the freshness or safety of an egg after performing these tests, it is always best to err on the side of caution and discard it. The potential risks associated with consuming spoiled eggs, such as foodborne illnesses like salmonellosis, far outweigh the cost of replacing a few eggs.