How long does Cornstarch last in the pantry once opened?
Turning the range into a date
Cornstarch keeps 18 months in the pantry once opened. Two clocks run on this item: one from the day it went into storage and one from the day the seal broke. Both are listed below, 2 rows in all.
- Unopened · in the pantryUse by18 months to 24 months after the day you bought it
- Once opened · in the pantryUse by18 months after the day you opened it
Sealed against opened
Opening the package costs 1.3 times here: 24 months sealed in the pantry against 18 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. On the same shelf it sits 18 of 52, between Yeast, packaged at 2 years and Sugar at 24 months. Corn and starch are the same food in the source 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 corn and starch.
- Unopened · in the pantry18 months to 24 months
- Once opened · in the pantry18 months
Can you freeze cornstarch?
The USDA prints no freezer time for cornstarch. Frozen at 0 °F any food stays safe; whether it is still good after thawing is a matter of quality. Keep the fridge at 40 °F or below and the freezer at 0 °F.
How to tell if cornstarch has gone bad
Go by the date first: cornstarch keeps 18 months in the pantry once opened. Insects, a musty or rancid smell, clumping from damp, or a swollen can mean it goes out. Any dish you cook with it follows the 2-hour rule, 1 hour above 90 °F.
Sources: USDA FSIS: the danger zone USDA FSIS: freezing and food safety FDA: are you storing food safely FoodSafety.gov: the FoodKeeper app.
Is it still safe to eat, or just past its best?
The answer at the top of this page reads 18 months in the pantry once opened. The USDA rating this place at all is the USDA saying Cornstarch keeps there, so the figure rates how good it will be. Past it, whether it has gone bad is yours to judge by look and smell: this window rates quality, not the day it turns hazardous.
It is past the date. Now what?
Say the calculator above puts Cornstarch past its 18 months in the pantry once opened window. Past that the calendar stops deciding and the food itself does. Mold takes the whole package out rather than the slice it grew on, and so does a musty or old-oil smell in a flour or a mix.
The whole rule, including the cases the source does not cover, is set out under what to do when the date has passed.
Items that behave the same way
The 6 items nearest it sit inside a band of 24 months to 2 years — a tight cluster, and this item at 24 months is inside it.
- Sugarkeeps exactly as long
- Chocolate, unsweetened and semi-sweet, solidkeeps 1 year in the pantry once opened
- Cornmealkeeps 6–12 months sealed in the pantryregular, degerminated · up to 2 years in the pantry once opened
- Vegetable oil sprayskeeps 1 year in the pantry once openedup to 2 years sealed in the pantry
- Sugar substituteskeeps 2 years sealed in the pantry
- Whole wheat flourkeeps 2 years in the fridge
Where these numbers come from
Every storage time on this page is the USDA’s own published figure from the FoodKeeper data, one of the 9 it keeps per food, reproduced unchanged and never an estimate of ours. Where the USDA lists several kinds under one name, each kind keeps its own windows, and the page names the kind its answer is for. The dates and multipliers are ours, computed from those ranges.
Source: USDA FoodKeeper, retrieved 1 September 2026. Found a figure that does not match the source? Tell us on the contact page. How the site is built is on the method page.
USDA index terms: corn, starch
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.