Does Cereal Go Bad? – Full Analysis

Does Cereal Go Bad? – Full Analysis

The two main factors to how fast cereal expires are: if the packaging is open or closed and if air gets into the package. There are four main types of cereal: high-fiber healthy cereal, whole-grain cereal, sugary cereal, and hot cereal.

Does cereal go bad? Yes, cereal does go bad. An unopened box of cereal can last about six to eight months in the pantry or cupboard. However, once you open the cereal box, its shelf life drops to 4-6 weeks. You can store cooked hot cereal in the fridge for up to four days.

How Long Does Cereal Last – Why Does Cereal Expire?

Unopened Cereal:

While each cereal has its own unique ingredients and are made for either health reasons or just to start the day with a sugar boost, most cereals have the same shelf life. As long as they are sealed shut in their packaging, Most cereals last anywhere from six to eight months. Six to eight months is the standard shelf life for most cereals, but it is always good to look at the expiration date on the bottom of the box to see when your specific brand of cereal expires. 

Opened Cereal:

However, once the package of cereal is open, its shelf life drops dramatically.  Once you open a bag of cereal, it will only last 4-6 weeks. Compared to unopened cereal, the shelf life of opened cereal is just a fraction of its original shelf life.

Cooked Hot Cereal:

Unlike the other cereals in the list above, hot cereal is the only type of cereal that you can store in the fridge and eat later. Once you cook hot cereal, allow it to cool and store it in the fridge in an airtight container. Hot cereals can last up to four days in the refrigerator.

How Long Does Cereal Last? Shelf Life [Chart]

Item Length of time
Cereal, unopened 6-8 months
Cereal, opened 4-6 weeks
Hot cereal, unopened 6 months
Hot cereal, cooked and stored in fridge 4 days

Why Does Open Cereal Expire So Quickly?

The sudden drop in shelf life is because the grains that make up the cereal are very susceptible to air. When someone opens a cereal bag, they usually just roll the excess plastic down and then place it back in the box. If they do not roll it down correctly, it will gradually spring back up over time, and the cereal inside the back will be exposed to air.

Cereal that is exposed to air overnight can become stale when the Sun rises. So it is very important to roll the cereal bag down properly. Some people may place tape over the plastic so it will not unfold.

Can You Eat Cereal after the Expiration Date?

Yes, you can eat cereal even after it has passed its expiration date. As long as the cereal looks and tastes fine, has no bugs crawling in it, and does not have any moisture inside the bag, it’ll be fine to eat.

But you should always test the expired cereal before you eat it. Cereal should maintain its freshness three months past its expiration date.

How to Know if the Cereal has Gone Bad

There are three ways to test if the cereal has gone bad. You should perform these tests before putting the cereal inside a bowl and pouring the milk over. The taste of the milk may mask any rotted or old taste the cereal is giving off.

When you open a package of cereal you suspect is going bad, grab a handful of the grains and smell it. If it no longer has a smell or now has a sour smell, then it is bad. Cereal develops a sour smell when it is affected by moisture. If moisture gets inside a cereal bag, it will quickly rot. 

When you taste the cereal, only take out a couple of flakes and taste with your tongue. Chew the cereal for a bit and see if the flavor has been affected. If the flavor is not as strong as it once was, or the grains are much harder and not as crunchy as before, then cereal is getting old.

Also, never eat cereal that has bugs crawling around inside of the package. These bugs have been eating the cereal and laying their eggs all over the grains. So, if you try to remove the bugs to eat the cereal, you will still be eating their eggs. That’s not the type of eggs you want for breakfast.

How to Store Cereal

Storing cereal correctly is quite easy. If it is not open, just leave it in its container and box and place it in a pantry or a cupboard. There is no need to fret about temperature fluctuations.

Once the cereal bag is open, every time you take out some cereal, it is important to roll the excess plastic down and make sure it does not open up again. Some people put their open cereal packages in the fridge. But the bag can still unfold and exposes the grains to air, so it will go bad anyway.

Types of Cereal

High fiber/healthy cereal: Grape nuts, Bran – If you ever want to start eating a heart-healthy breakfast that is low in cholesterol and full of fiber, then this is the cereal category that’s best for you. Just don’t expect a lot of sugary flavors. It’s made for health, not for fun.

Whole-grain cereal: Whole grain cereals tend to be more flavorful and less fibrous than the high fiber healthy cereals. This type of cereal is also on the healthy side, but it does have more sugar.

Sugary cereal: Cinnamon Toast Crunch, Frosted Mini-wheats, Lucky Charms – These are the cereals we grew up with as children. Once you put a spoonful of this cereal in your mouth, expect to be overloaded with a massive hit of sugar. Stay away from these cereals if you’re a diabetic

Hot cereal: Many people have not tried hot cereal. It is not like oatmeal. Hot cereal is porridge, and it is made by grinding up grains and cereal and boiling them. 


  • There are four main types of cereals: hot cereal, high-fiber cereal, whole-grain cereal, and sugary cereal.
  • Hot cereal is sometimes made with oatmeal, but not always. An unopened package of cereal can last six to eight months in the pantry or cupboard.
  • Once a cereal package is open, it will just last one month to six weeks.
  • The most common reason why cereal expires so quickly after it is open is because of air exposure.
  • Hot cereal is the only cereal that can last up to 4 days in the fridge.
  • As long as you’re careful and perform the smell and taste test, you can eat cereal after its expiration date.
  • There are two ways to know if cereal has gone bad: by smell and by taste.
  • Do not eat cereal if it has maggots or other bugs crawling around inside the bag.