How to Store Half an Onion (So You Actually Use It)

Half an onion sitting on your counter is about $0.40 of produce and roughly a 50/50 shot at actually using it before it shrivels into something unrecognizable. The fix is fast: store it cut-side down in an airtight container or zip-lock bag in the fridge, and it stays fresh for up to a week, per Simply Recipes, or up to two weeks if you’re diligent about the seal, per America’s Test Kitchen. If you know you won’t touch it for a while, the freezer is a better bet. That’s the whole answer.

If you’re trying to figure out how to store half an onion, the answer takes about ten seconds: cut-side down, airtight container or zip-lock bag, straight into the fridge. The rest is just the details.

How to Store Half an Onion in the Fridge: Two Small Habits That Actually Matter

The cut-side-down rule isn’t fussy. It just protects the exposed surface from drying out. Southern Living recommends keeping the skin on where possible, for the same reason, it’s a moisture barrier, not decoration.

After that, the container matters more than most people think. A loose sheet of plastic wrap is not an airtight container. A proper zip-lock bag with the air pressed out, or a lidded container with a real seal, is what gets you to that one-to-two-week window. Food Republic puts the range at five days to a week for an airtight container, which tracks with real kitchens, where “I’ll use it Thursday” often becomes “wait, what day did I use this.”

If your onion is going into a raw application, a salad, a sandwich, a quick chicken adobo, refrigerate it and use it within the week while the texture is still crisp.

When to Freeze Instead

The freezer is the right call when you know you’re not using it raw. Food Republic puts frozen onion at three to six months at 0°F, which is a long runway. Cook’s Illustrated is clear that frozen onions should go only into cooked dishes, soups, stews, stir-fries, because the texture softens after thawing.

The technique: chop or slice before freezing, spread in a single layer on a baking sheet first, then transfer to a bag once frozen. Southern Living recommends the single-layer step to prevent one giant onion brick that you have to chip apart at 6pm on a Tuesday.

Pantidy tracks what’s in your fridge and freezer on iOS and Android with expiration alerts, so that half onion doesn’t vanish into the forgotten lands behind the ketchup. Free to try for 14 days.

Frequently Asked Questions

How long does a half onion last in the fridge?

The best way to store half an onion is cut-side down in an airtight container or zip-lock bag; stored that way, it lasts up to a week, per Simply Recipes and potentially up to two weeks, per America’s Test Kitchen.

Should I store a cut onion cut-side up or cut-side down?

Cut-side down. Southern Living recommends placing the cut face down and keeping the skin on where possible to slow moisture loss. It’s a small habit that makes a real difference in how long the onion stays usable.

Can you freeze half an onion?

Yes. Chop or slice it first, freeze in a single layer, then transfer to a sealed bag. Frozen onion keeps for three to six months at 0°F, but use it only in cooked dishes, soups, stews, sautés, since the texture softens after thawing.

Why does my cut onion smell up the fridge?

An onion’s sulfur compounds release as soon as you cut it, and a loose wrap just lets them circulate freely. A proper airtight container or a well-sealed zip-lock bag keeps the smell contained and the onion fresher longer.

Keeping the skin on where possible also helps keep cut onion fresh longer, since the outer layer acts as a moisture barrier.

Two problems, one fix.

Today’s action: grab whatever half onion is in your fridge right now, flip it cut-side down, press it into a zip-lock bag, and check how long onions actually last before your next grocery run. Thirty seconds, and you’ve just extended its life by days.