How long doesCornstarchlast in the pantry once opened?

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.

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

Turning the range into a date

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

Is this window about safety or about taste?

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, 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 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 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?

2 items in the Baked Goods list keep exactly as long as this item, 24 months, so they all share place 18 of 52 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 68% of them.

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 months sealed in the pantryregular, degerminated · up to 2 years in the pantry once opened
• Chili powderkeeps 2 years in the pantry once opened
• Whole wheat flourkeeps 2 years in the fridge
• Butter flavorkeeps 12 months in the pantry once openedup to 2 years in the pantry

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 Diet powder mixes and drink mixes, Textured soy protein and Chocolate, and the rest of that group is what the list below draws on. Of the 8 shown, 7 keep longer than this one.

• Diet powder mixes and drink mixes1 month in the pantry once openedup to 24 months sealed in the pantry
• Textured soy protein3 months in the pantry once openedup to 2 years sealed in the pantry
• Chocolate1 year in the pantry once opened
• Vegetable oil sprays1 year in the pantry once openedup to 2 years sealed in the pantry
• Shortening6 months in the pantry once openedup to 2 years sealed in the pantry
• Chili powder2 years in the pantry once opened
• Seasoning blends1 year in the pantry once opened
• Beans1 year in the pantry once opened

The rest of the Baking and Cooking shelf

The USDA puts this product on the Baking and Cooking shelf together with 34 others, and 17 of them keep longer outside the freezer. The shelf runs from Baking soda at 3 years down to Herbs at 10 days. Nearest this product by window are Sugar, Chocolate and Cornmeal, which is the order the list below is printed in. The order counts the longest window outside the freezer, so this item sits here at 24 months rather than at the 18 months in the pantry once opened its own answer prints.

• Sugar24 months18 months in the pantry once opened
• Chocolate2 years1 year in the pantry once opened
• Cornmeal2 years6 months sealed in the pantry
• Vegetable oil sprays2 years1 year in the pantry once opened
• Shortening2 years6 months in the pantry once opened
• Chili powder2 years2 years in the pantry once opened
• Seasoning blends2 years1 year in the pantry once opened
• Sugar substitutes2 years2 years sealed in the pantry

If it has to keep longer than this

Nothing the USDA files under Baked Goods keeps at least twice as long as this one outside the freezer. It runs the other way: 28 entries in the category keep half as long or less, among them Fruit cake, Flour and Frosting or icing. So the question this page answers is not what to buy instead, but what this product outlasts on the same shelf, and by how much. Twice as long is the cutoff used here, so a product a few days apart from this one is not treated as a step.

• Fruit cake12 months6 months sealed in the pantry
• Flour12 months6 months in the pantry once opened
• Frosting or icing12 months2 weeks in the fridge once opened
• Gelatin12 months3 months in the pantry once opened
• Oils12 months3 months in the pantry once opened
• Nut oils12 months6 months in the fridge once opened
• Tamarind paste12 months6 months in the pantry once opened
• Tapiocas12 months12 months in the pantry once opened

The record this page is built from

This page is built from a single FoodKeeper row, record 220 — the source’s own number for it, not a position — one of the 661 rows in the snapshot. That row fills 2 of the nine storage slots with a time, and the binding figure on it is printed by the source in months, which is the unit this page keeps rather than converting it to days. The same record answers to corn and starch 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: 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.