But anyone who shops for eggs knows that they are one of the most perplexing foods to buy. The cartons are covered with labels and claims, the most cryptic of which are the numerical codes that indicate the eggs’ pack and expiration dates.
Those codes are there to help you gauge egg freshness: They indicate when the eggs were processed after being laid and how long they’re expected to keep in the fridge—which is typically 3 to 5 weeks. But the codes are not self-explanatory, nor are they a definitive way to gauge how long eggs will last, so we’re going to do some decoding for you here.
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What Do the Numbers on an Egg Carton Mean?
Eggs graded by the U.S. Department of Agriculture (USDA) are required to display the pack date, also known as the Julian date, which refers to the day the eggs were washed, graded, and placed in the carton. Generally, eggs are packed within a week of being laid, but legally the pack date can be as much as 30 days from the day they were laid.
The pack date is listed as a three-digit number, often beneath or above the “sell-by” or “expiration” (EXP) date—if one is provided. Unlike the pack date, sell-by and EXP dates are not federally regulated, but might be required by the state in which the eggs are sold.
How to Read the Pack/Julian Date
The pack date numbers run consecutively, starting with 001 for January 1 and ending with 365 for December 31. So, for example, 078 would indicate that the eggs were packed on March 19. (The pack date may follow a set of numbers beginning with a “P”; this is a code indicating the packing plant.)
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How Long Do Eggs Last?
The USDA recommends purchasing eggs before the sell-by or EXP date, refrigerating them, and using them within 3 to 5 weeks. The sell-by date will usually expire within that time frame, but the USDA assures that they are safe to use.
In fact, we tasted two- and three-month-old eggs that were perfectly palatable. At four months, the white was very loose (and the yolk developed faint off flavors), but was still edible.
Bottom line: Since a carton of eggs may be up to two months old by the end of the sell-by date, the pack and sell-by dates are by no means an exact measure of egg freshness; they provide vague guidance at best.
Use your discretion: If an egg smells odd or displays discoloration, pitch it. Older eggs also lack the structure-lending properties of fresh eggs—the white and the yolk loosen over time—so beware when baking. When we whipped four-month-old eggs, they rapidly deflated.
Testing Freshness: Does the Egg in Water Test Work?
Some sources suggest that you can check freshness by putting eggs in a bowl of water: Fresher eggs are more likely to sink, while older ones are more likely to float because the air sack expands over time.
However, we found that wasn’t a reliable test, because eggs didn’t float until they were four to six months old. The safer bet is to just check the pack date.
When Does Egg Freshness Matter Most?
As eggs age, the white and yolk loosen. For some applications, such as scrambling, this doesn’t matter much because the white and yolk get mixed together. For others, such as poaching, this can dramatically affect the outcome: Egg whites contain both thick and thin portions, and fresher eggs contain a higher percentage of the thick kind that plumps up nicely when cooked, while the thinner portion becomes wispy and ragged.
Want to learn more egg carton terminology? Cook’s Illustrated Editor in Chief Dan Souza and Senior Content Editor Alyssa Vaughn sort through a lot of other (often confusing, sometimes misleading) labels in this article about how to read an egg carton. (There’s even more context in this episode of What’s Eating Dan?.)