The Ultimate Guide: 5 Proven Ways To Tell If An Egg Is Bad (Even Weeks Past The Date)

The question of whether your eggs are still safe to eat is one of the most common kitchen dilemmas, especially when you find a carton lurking in the back of the refrigerator past its printed date. Fortunately, knowing how to check for spoilage is less about trusting the "best-by" date and more about understanding a few simple, highly reliable scientific principles. As of December 2025, food safety experts confirm that your senses—sight, smell, and a simple water test—are far more accurate indicators of an egg's freshness than any date on the carton. The good news is that eggs stored properly at a constant cold temperature (40°F or below) can often remain safe to consume for several weeks, even up to two months, beyond the carton's printed date. The key to confident cooking lies in a three-step inspection process that starts before you even crack the shell. We'll break down the definitive methods, from the famous "float test" to deciphering the cryptic Julian date code, ensuring you never waste a perfectly good egg again.

The Definitive Float Test: Understanding the Air Cell

The float test is the most famous and arguably the easiest way to gauge an egg's age without breaking it. This method relies on the natural structure of the egg and how it changes over time.

The Science Behind the Float:

An eggshell is a semi-porous structure, meaning it contains thousands of tiny pores. Over time, the protective outer layer, known as the cuticle or bloom, wears down, allowing a small amount of moisture inside the egg to evaporate slowly. This evaporation causes the small internal air cell—located at the blunt end of the egg—to grow larger. The larger the air cell, the more buoyant the egg becomes in water.

How to Perform the Float Test:

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Gently place the egg in a bowl or glass filled with cold water. Observe its behavior:

• Sinks and Lays Flat: This egg is very fresh, likely laid within the last week. The air cell is tiny.
• Sinks but Stands on End (Vertically): This egg is older, perhaps 2–3 weeks old, but still perfectly safe to eat. The air cell has grown, but not enough to cause it to float. Use this egg for hard-boiling, as it will be easier to peel.
• Floats to the Surface: This is a definitive sign that the egg is rotten and should be discarded. The air cell is large enough to make the egg extremely buoyant.

The Smell and Sight Check: The Most Reliable Indicators

While the float test is great for gauging age, your nose and eyes are the ultimate defense against consuming a truly bad egg. A foul odor is the clearest, most reliable sign of spoilage.

1. The Smell Test (The Gold Standard):

A fresh egg should have little to no odor. A slightly older, but still good, egg might have a very mild, damp straw-like smell. If you suspect an egg is bad, crack it onto a plate or into a separate bowl before adding it to other ingredients. If you catch a whiff of a strong, foul, or sulfurous smell (like rotten gas), the egg has gone bad and must be immediately discarded.

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2. The Visual Shell Inspection:

Before cracking, inspect the shell itself. Look for signs of contamination or bacterial growth:

• Slime or Chalkiness: A slimy or chalky exterior can indicate the presence of bacteria or mold growth.
• Cracks or Damage: Cracks compromise the shell's integrity, allowing contaminants like Salmonella to enter easily.
• Brown or Green Spots: While rare, a brown shell or visible mold is a clear sign of spoilage.

3. The Cracked Egg Test:

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Once cracked, the appearance of the albumen (egg white) and the yolk will tell you everything you need to know about its quality:

• Fresh Egg: The yolk will be round, firm, and sit up high. The egg white (albumen) will be thick and tightly gathered around the yolk, not spreading significantly.
• Older (But Still Good) Egg: The yolk will be flatter, and the egg white will be thinner and spread out more easily. This is still safe to eat.
• Bad Egg: Look for a watery or gray yolk, or an egg white that appears pinkish, iridescent, or has any cloudy discoloration. These are signs of Pseudomonas bacteria, which can cause spoilage.

Decoding Egg Carton Dates and Storage Facts

Understanding the codes on your egg carton is crucial for maximizing shelf life and reducing food waste. The dates printed are not typically "expiration" dates, but rather guides for peak quality.

Sell-By vs. Best-By Date:

The "sell-by date" is a retailer's guide, indicating how long the store should display the eggs for sale. The "best-by date" or "use-by date" indicates when the egg is expected to be at its peak quality. Under ideal refrigeration conditions (kept at 40°F or below), eggs are typically safe to eat for 4–5 weeks past the pack date, regardless of the "best-by" date.

The Julian Date Code: The True Freshness Marker

If you want to know exactly when your eggs were packaged, look for the Julian date code. This is a three-digit number, ranging from 001 (January 1st) to 365 (December 31st), and it represents the consecutive day of the year the eggs were washed, graded, and placed in the carton. This code is the most accurate measure of an egg's true age.

Key Storage Tips for Maximum Freshness:

• Always store eggs in their original carton on an inner shelf of the refrigerator, not in the door, where temperature fluctuations are common.
• Do not wash eggs before storing them. The washing process removes the natural protective coating (the cuticle), which helps prevent bacteria from entering the shell's pores.
• Keep eggs away from strong-smelling foods, as the semi-porous shell can absorb odors.

By relying on the combination of the float test, the smell test, and a visual inspection of the cracked egg, you can confidently determine the freshness of your eggs and safely enjoy them, often long after the carton's printed date.