In the Test Kitchen, we go through a lot of eggs to test. At home, though, we work through our cartons at a more regular clip, and considering the price of eggs lately, we want to be sure to use them wisely so we don’t waste any of our investment. After one of our editors recently dropped more than $8 on a dozen at a Midwest supermarket, she came into the office to ask, “do eggs expire, or is this another scenario in which it’s totally safe to eat a food past its expiration date?”

We hopped down to the Test Kitchen and called up a couple of the food safety experts we have on speed dial to help you crack into the truth about how to tell if your eggs are bad. Turns out, that “best by” date isn’t your best indicator of the age of your eggs. Read on to find out what is.

Do Eggs Expire?

You know the drill when you’re shopping for eggs: Open the lid and check for cracked eggs. Peek at the “sell by” date to ensure it hasn’t already passed. If that carton passes those two tests—by featuring damage-free shells and being labeled with a date that’s at least a week or two in the future—many shoppers (us included) add them to their carts.

But even if the “sell by” date has come and gone, that doesn’t necessarily mean an egg has gone bad. According to Sarah Brekke, M.S., Better Homes & Gardens Test Kitchen brand manager, “it’s often safe to eat eggs past their expiration date. The date on the carton is often a ‘sell by’ or ‘best by’ date, not an ‘expiration date.’” 

As long as you cook eggs to their safe recommended temperature, they should be perfectly safe to enjoy for up to 3 to 5 weeks after purchase— yes, even if the date on the carton falls within that time frame—the USDA confirms. (This sentiment is echoed by the Egg Safety Center of the American Egg Board.)

What’s so special about that 5-week mark? First of all, the longer you store an egg, the higher the chance it might crack or be exposed to wide variations in temperature; two factors that can speed up spoilage and possibly increase the risk of bacterial contamination.

The second reason why time is of the essence boils down to a rare, but possible, food safety issue. About 3 in 10,000 eggs are laid with Salmonella. This is a type of bacteria that, if consumed, can lead to an infection in the intestinal tract. 

Salmonella lives in the egg white, and natural preservatives in egg whites will stop the bacteria from multiplying, explains Donald Schaffner, Ph.D., a distinguished professor of food microbiology and extension specialist at Rutgers University in New Brunswick, New Jersey. But over time, a membrane that separates the yolk from the rest of the egg begins to break down. Once it disintegrates enough, “any potential Salmonella in the white can move to the yolk where there are no inhibitors and they can start to grow,” Dr. Schaffner tells BHG. “As the Salmonella concentration increases, the food safety risk increases.” 

Higher storage temperature promotes a faster breakdown of the yolk membrane and allows for more rapid bacterial growth, he adds. Salmonella will not grow at proper refrigeration temperatures (40° F or below) even if the yolk membrane has broken down and the Salmonella gets into the yolk.

So again, as long as you’re refrigerating your eggs and cooking them to a safe temp, the food safety risk with eating eggs is very rare. This is even if your carton does contain one of those rare eggs contaminated with Salmonella. Still, to be on the safe side—and to have an easier time separating eggs and the best flavor no matter how you cook your eggs—it’s best to eat your eggs within 5 weeks of the packing date and during about a 3-week window after you buy them, according to the American Egg Board.

 Egg Label Lingo, Decoded

Dr. Schaffner and Brekke walk us through what we can learn by simply looking at the numbers stamped on the side of the egg carton.

• Sell by date: The recommended date by which a retailer should aim to sell the eggs. If both happen to be listed, this is almost always earlier than the best by date.
• Best by or best before date: The date on which the egg brand recommends you try to enjoy them for optimal flavor, texture, and the least food safety risk.
• P Number: Each egg plant is assigned a number, and this refers to the specific plant where the eggs were packed in.
• Julian date, or pack date: The day of the year (from 001 to 365) during which the eggs were packed. “This is usually found on the short side of the carton and represents the consecutive days of the year with the number 001 as January 1 and December 31 as 365,” Dr. Schaffner says.

Since the sell by and best by date’s frequently err on the conservative side, the experts we spoke to confirm the most helpful number to note on an egg carton is actually the Julian or pack date. Do the math to figure out the date the eggs were packed and add 5 weeks. Mark that as the date to aim to enjoy your eggs before.

How to Tell if Your Eggs Have Gone Bad

Besides referring to the dates on the carton, Brekke says that the following tests can help you pinpoint an egg that might be spoiled.

• Smell the egg. A fresh egg has no smell, while a spoiled egg can smell rotten or sulfurous.
• Do a float test. Place the egg in a bowl of water. If it sinks, it’s fresh. If it floats and tilts vertically (picture the egg “back floating” long-ways on top of the water), it may be spoiled.
• Shake the egg vigorously near your ear. If the egg makes a sloshing noise, it may be spoiled. If it doesn’t make a sound, the egg is likely still good.
• Peek at the egg whites. Crack the egg in question and examine the whites. Fresh egg whites are slightly opaque and thick in consistency. An egg might be bad if the whites appear watery or clear, and you should definitely discard any eggs with green or iridescent whites.

How to Store Eggs to Max Out Their Shelf Life

Follow these pro tips from Brekke and Meredith Carothers, food safety specialist for the USDA’s Food Safety and Inspection Service in Washington D.C., to max out the safe shelf life of raw eggs:

• Take eggs straight home from the store and store them as quickly as possible in the refrigerator set at 40° F or below.
• Keep the eggs in their carton (to reduce the risk for cracking or odor absorption) and place them in the coldest part of the refrigerator, not in the door, to keep the temperature as consistent as possible.
• Avoid washing eggs, as this may remove the natural protective layer on the egg and make them more susceptible to bacterial growth.

Do not attempt to freeze whole eggs, “because the shell may crack,” Dr. Schaffner confirms.