Almost everyone has been faced with this conundrum — you reach into the fridge for an egg, but can't remember how long they have been sitting there.
It's true that over time, an egg's quality begins to decline as the air pocket inside gets larger and the whites get thinner. However, an egg only "goes bad" when it starts to decompose because of bacteria or mold.
In fact, your eggs may be perfectly good to eat for many more weeks.
When in doubt, there are several methods you can use to determine if your eggs are good or bad. Here are the top five.
1. Check the Expiration Date
One of the easiest ways to tell if your eggs are still good is to check the date on the carton. But if you throw your refrigerated eggs out as soon as this date arrives, you could be wasting perfectly good eggs.
In the US, eggs may be labeled with either a "sell by" or expiration date, depending on which state you live in, in order to let you know if your eggs are still fresh.
A "sell by" date indicates how long a store should offer eggs for sale — no more than 30 days after packing — but not necessarily that the eggs have gone bad ().
An expiration date, on the other hand, marks the date after which the eggs are considered less than fresh.
If neither of these labels is present, there is yet another date you can look for to tell how fresh your eggs are.
Eggs that have been graded by the USDA are required to show the "pack date" on the carton, which is the day that the eggs were graded, washed and packaged. But you may not recognize it if you don't know what to look for.
The "pack date" is printed as a Julian date, meaning each day of the year is represented by a corresponding, chronological number. Therefore, January 1st is written as 001 and December 31st as 365 ().
If your eggs are still within the expiration or "sell by" date on the carton, or within 21–30 days after the "pack date," you can be pretty sure they are still fresh.
And even though the quality of an egg may start to decline after a certain date, it may still be good to eat for several weeks — especially if it has been refrigerated, which preserves quality and prevents bacterial growth ().
However, if your eggs are past the date printed on the carton, you may need to use another method to tell if the egg is good or bad.
Summary: Checking the "sell by," expiration or "pack date" on an egg carton can tell you if an egg is still good. But just because an egg has passed its date does not always mean it has gone bad.
2. Conduct a Sniff Test
The sniff test is the oldest, simplest and most reliable method of telling whether an egg has gone bad.
If you find that your eggs are past their "sell by" or expiration date, you can tell if they are still good with a simple sniff.
Eggs that have gone bad will give off an unmistakable smell, regardless of whether they are raw or cooked ().
If you can't already tell while the egg is in the shell, crack the egg onto a clean plate or bowl and give it a sniff.
If anything smells off, toss the egg and wash the bowl or plate with hot, soapy water before using again.
If things smell normal, meaning there is no odor at all, that's a good sign that the egg is still safe to use ().
Summary: Sniffing either a raw or cooked egg is a simple but reliable way to tell if an egg has gone bad.
3. Complete a Visual Inspection
In addition to your nose, your eyes are a valuable tool for telling whether an egg is good or bad.
While the egg is still in its shell, check that the shell is not cracked, slimy or powdery.
Sliminess or cracks can indicate the presence of bacteria, while a powdery appearance on the shell may indicate mold ().
If the shell appears dry and undamaged, crack the egg into a clean, white bowl or plate before using. Look for any pink, blue, green or black discoloration in the yolk or whites, as this may indicate bacterial growth (, ).
If you notice any signs of discoloration, throw the egg out and wash the bowl with hot, soapy water before testing a new egg.
You can also check to see if the whites or yolk of the egg are runny. This is an indication that the egg is old and that the quality has declined. But this does not necessarily mean it has gone bad, and it can still be perfectly fine to use ().
Summary: In addition to sniffing an egg, check its shell for signs of bacteria and mold. Inspecting the whites and yolk for discoloration is also a good strategy.
4. Perform a Float Test
The float test is one of the most popular methods for checking whether an egg is good or bad.
This is also a common method for determining the age of a fertilized egg that is developing into a chick (, ).
It works just as well to judge whether an unfertilized table egg is fresh or not.
To perform the float test, gently set your egg into a bowl or bucket of water. If the egg sinks, it is fresh. If it tilts upwards or even floats, it is old.
This is because as an egg ages, the small air pocket inside it grows larger as water is released and replaced by air. If the air pocket becomes large enough, the egg may float.
While this method may tell you whether an egg is fresh or old, it doesn’t tell you whether an egg is good or bad ().
An egg can sink and still be bad, while an egg that floats may still be fine to eat ().
Summary: Checking whether an egg sinks or floats is a popular way to check how fresh it is. However, it can't tell you if an egg has gone bad.
5. Candle Your Eggs
Candling is a method used either to assess the quality of a table egg or to assess the development of the chick in a fertilized egg.
This is done industrially using specialized equipment to ensure the proper grading of table eggs before they are packaged.
But it can also be done on your eggs at home, if you're willing to learn.
You'll need a dark room and a small, bright source of light. In the past, candles were used, hence the name "candling." Yet it is probably more effective to use a small flashlight or reading light instead.
Hold the light source up to the large end of the egg. Then, tilt the egg and turn it quickly from left to right. If done correctly, the contents of the egg should be illuminated ().
This allows you to see whether the egg's air cell is small or large. In a very fresh egg, the air cell should be thinner than 1/8 inch, or 3.175 mm. As the egg ages, gasses replace water lost through evaporation, and the air pocket will get larger ().
You should also be able to tell by moving the egg from side to side how firm the egg white and yolk are. Less movement indicates a fresher egg ().
Candling may require some practice, but it allows you to reliably identify if an egg is fresh or old. Yet, like the float test, it cannot tell you if an egg has gone bad.
Summary: Candling is a more difficult but reliable way of checking how fresh an egg is. However, it doesn't tell you if an egg is bad.
The Bottom Line
A lack of knowledge about how to tell when an egg has gone bad leads some people to needlessly throw away good eggs.
Among the five strategies listed here, cracking an egg open, giving it a sniff and checking for discoloration is the most conclusive method of determining freshness.
Keep in mind though that eggs containing bacteria that cause food-borne illness, such as Salmonella, may look and smell completely normal.
So don't forget that even if an egg passes these tests, it's important to fully cook it to a safe temperature before you eat it.