How long doesCereallast in the pantry once opened?
The USDA rates 2 kinds of this separately
The USDA files 2 separate entries under this name — ready-to-eat and cook before eating (oatmeal, etc.) — and gives every one of them the same window outside the freezer, 6 months to 12 months. They are separate rows in the source rather than separate answers to the question.
Sealed against opened
Opening the package costs 4 times here: 12 months sealed in the pantry against 3 months open in the pantry. That is a real difference and worth dating the container for, but not the collapse it becomes for the more perishable items in the same list.
Every storage figure the USDA publishes for this item
The USDA rates this item in the pantry and nowhere else, one of 84 foods of the 466 it files that way. The source also indexes it as ready, eat, cook before eating and oatmeal.
Cereal, ready-to-eat
- Unopened · in the pantry6 months to 12 months
- Once opened · in the pantry2 months to 3 months
Cereal, cook before eating (oatmeal, etc.)
- Unopened · in the pantry12 months
- Once opened · in the pantry6 months to 12 months
Turning the range into a date
Each kind gets its own dated rows here, 4 rows across the 2 the USDA lists under this name, because a date is only worth printing against the window it belongs to.
Cereal, ready-to-eat
- Unopened · in the pantryUse by6 months to 12 months after the day you bought it
- Once opened · in the pantryUse by2 months to 3 months after the day you opened it
Cereal, cook before eating (oatmeal, etc.)
- Unopened · in the pantryUse by12 months after the day you bought it
- Once opened · in the pantryUse by6 months to 12 months after the day you opened it
Is this window about safety or about taste?
The answer at the top of this page reads 2 months to 3 months in the pantry once opened. The USDA rating this place at all is the USDA saying Cereal, ready-to-eat keeps there, so the figure rates how good it will be. Past it, judge it by look and smell: this window rates how good the food will be, not the day it becomes a hazard.
Every figure assumes the food was sound when you stored it, that your refrigerator holds 40 °F or below and your freezer 0 °F or below, and that the package was handled normally.
It is past the date. Now what?
Say the calculator above puts Cereal, ready-to-eat past its 2 months to 3 months in the pantry once opened window. Past that the calendar stops deciding and the food itself does. A rancid, paint-like smell in a nut, an oil or a seed, mold around the neck of a bottle, or a swollen can mean it goes out whatever the date says.
The FoodKeeper entry this page is built from prints storage times and nothing else, so anything past them here is USDA and FSIS guidance rather than a figure from the source. The whole rule, including the cases the source does not cover, is set out under what to do when the date has passed.
Is that a long time?
10 items in the Shelf Stable Foods list keep exactly as long as Cereal, ready-to-eat, 12 months, so they all share place 38 of 70 rather than being put in an order the data does not support. Among the 244 foods the USDA also gives a pantry figure, it keeps longer than 41% of them.
Items that behave the same way
All 5 of the 6 items nearest Cereal, ready-to-eat keep exactly as long as it does, 12 months, so the ranking around it is a tie rather than an order.
Products the USDA rates in the same places
This is a common shape of record: 30 of the 466 products are rated in the same places, pantry from the day of purchase and pantry after opening, and 7 of the nine slots are left blank on all of them. Sorted by how close their windows are to this one, the nearest are Gelatin, Tapiocas and Toaster pastries, and the rest of that group is what the list below draws on. Of the 8 shown, 5 keep longer than this one. The longest-keeping of them is Lentils at 1 year.
- Gelatin3 months in the pantry once openedflavored · up to 12 months sealed in the pantry
- Tapiocas12 months in the pantry once opened
- Toaster pastries1 week in the pantry once openedup to 12 months sealed in the pantry
- Lentils1 year in the pantry once opened
- Peas1 year in the pantry once opened
- Marshmallows1 month in the pantry once openedup to 1 year sealed in the pantry
- Pudding mixes3 months in the pantry once openedup to 1 year sealed in the pantry
- Soup mixes1 year in the pantry once opened
The rest of the Shelf Stable Foods shelf
The USDA puts this product on the Shelf Stable Foods shelf together with 69 others, and 37 of them keep longer outside the freezer. The shelf runs from Coconut cream at 5 years down to Polenta at 7 days. Nearest this product by window are Toaster pastries, Macadamias and Peanuts, which is the order the list below is printed in. Across the whole of Shelf Stable Foods the same product ranks 38 of 70. The middle of the shelf is Sunflower oil, at 1 year. 5 products on this shelf publish no window outside the freezer and stay out of the order.
- Toaster pastries12 months1 week in the pantry once opened
- Macadamias12 months12 months sealed in the fridge
- Peanuts12 months12 months sealed in the fridge
- Pistachios12 months12 months sealed in the fridge
- Walnuts12 months9 months sealed in the fridge
- Dry stuffing mix12 months9 months in the pantry
- Sunflower seeds12 months7 months in the fridge once opened
- Grits12 months12 months sealed in the pantry
If it has to keep longer than this
If it has to keep longer than 12 months, the Shelf Stable Foods aisle gives 22 products that hold at least twice as long outside the freezer. The smallest step up is Peanut butter at 24 months against this one's 12 months; after it come Chocolate syrup, Molasses and Popcorn. They are printed below in the order the step gets bigger, not alphabetically. In the other direction, 15 entries in the category keep half as long or less, Fruits, dried and Cashews among them. The largest step the category offers is Sesame seeds at 5 years.
- Peanut butter24 months2 months in the pantry once opened
- Chocolate syrup2 years6 months in the fridge once opened
- Molasses2 years6 months in the pantry once opened
- Popcorn2 years1 year in the pantry once opened
- Black pepper2 years2 years sealed in the pantry
- Cajun seasoning blend2 years1 year sealed in the pantry
- Flaxseed2 years2 years sealed in the pantry
- Almond oil2 years2 years sealed in the fridge
The record this page is built from
The USDA publishes 2 separate rows under this name — records 374 and 375 — and this page carries all of them rather than picking one, because their windows differ. Between them they fill 2 of the nine storage slots with a time. Comparisons and the place in the category are computed for Cereal, ready-to-eat, which is the kind the plain name means here, chosen kind by kind rather than by the order the source happens to list them in. The same record answers to ready, eat, cook before eating and oatmeal in the source's own index.
Where these numbers come from
Every range on this page is published by the USDA FoodKeeper and reproduced unchanged. The multipliers, the rankings, the percentages and the dates are ours, computed from those ranges. Where the source gives a span such as 3 to 5 weeks, comparisons use the upper figure, and the full span is always printed.
Rankings cover only the items the USDA gives a usable figure for, and identical ranges share a place rather than being ordered arbitrarily. Neighbors are chosen by nearest storage time within the same category, never alphabetically: two foods filed next to each other by name usually have nothing to do with each other. The freezer is excluded from ranking because it flattens almost everything.
Where the USDA lists several kinds under one name, they share one page here and every kind keeps its own windows: the source prints them as separate rows, and a page that merged them would be inventing a figure the source never published. Comparisons and the place in the category are computed for the kind the plain name means — the shell egg for eggs, the can for tuna — which is settled name by name rather than by the order the source lists its rows in, and the page names it. Where the plain name means no single kind, the page prints no single figure at all and lists the kinds instead.
Source: USDA FoodKeeper, retrieved 1 September 2026. This site computes every comparison on this page and takes responsibility for it. Found a figure that does not match the source? Tell us on the contact page, with the page and the row — the parsing is mechanical, so a mismatch is our bug and we want it. How the whole site is built, which figures are ours and where the source can be checked is on the method page.
USDA index terms: cook before eating, eat, meal, oat, oatmeal, oats, ready
KeepsUntil is an independent reference built on public USDA data. It is not affiliated with, endorsed by, or connected to the U.S. Department of Agriculture or the Food and Drug Administration. Whether a given window is a safety limit or a quality window is stated on the page that prints it.