A lot of people rely on the date on the packaging to tell them when food has gone bad, even with eggs, but the sell-by dates are often somewhat arbitrary and are not expiration dates. If you've been tossing your eggs based on the dates on your carton—you could be wasting perfectly good food. Eggs are often still good to eat long after the date on the packaging says to throw them out. If you want to test how fresh they are before finding out the hard way, here are a few methods for testing them. Your eyes and nose are the best tools for determining freshness with meats, produce and herbs — it's pretty obvious when something's moldy or smelly. But you can't smell and see an egg before you crack it (unless you're highly skilled), so how do you tell if it's still good? Image via Shutterstock

The Best Method for Uncracked Eggs: The Float Test Just fill a bowl with cold water and place your eggs in the bowl. If they sink to the bottom and lay flat on their sides, they're very fresh. If they're a few weeks old but still good to eat, they'll stand on one end at the bottom of the bowl. If they float to the surface, they're no longer fresh enough to eat. Don't Miss: The Best Way to Test Baking Soda/Powder for Freshness While you could fry or scramble an egg that's on its side or standing upright, when it comes to hard-boiling, you'll want the upright ones, as Yumi points out in her guide to peeling hard-boiled eggs. The extra air in the older eggs will help the peel come off easier after hard boiling. Image by Yumi Sakugawa/WonderHowTo Below, you can see what a really old egg looks like in comparison to really fresh one. The one on the left is most likely 3 or more months old (from when it was laid, not the date you bought them). Image via Sturgis To give you an idea of hold old an egg is, look at the "packed by" dates on the carton, which are in Julian date form by the "sell by" dates. Julian dates range from 1 to 365 days, and since most companies pack their eggs shortly after being laid, it's a good indicator. Image via FDA

Why the Float Test Works So Well The reason this method works is that the eggshells are porous, which means they allow some air to get through. Fresh eggs have less air in them, so they sink to the bottom. But older eggs have had more time for the air to penetrate the shells, so they're more buoyant and will float.

The Best Method for Cracked Eggs: The Plate & Sniff Test If you don't need the shell intact, you can also crack the egg onto a plate or other flat surface to test how fresh it is. If it's fresh, the yolk should be bright yellow or orange, and the white shouldn't spread much. If you're not sure, give it a good sniff: fresh eggs shouldn't have much of a smell at all. Image via Rouxbe The yolk will be flatter and the white will be much runnier in an older egg. An egg that spreads out when cracked isn't necessarily bad, though, just older (and again, good for hard-boiled eggs). If it's gone bad, you probably won't even need to do the sniff test—even slightly rotten eggs will have a very strong, distinct smell you'll notice right away.

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