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Bevel & Bone

HUB 03 · Guides

How to Cut an Onion

The cut you'll make more than any other. Done right it's fast, even, and safe — and a sharp knife genuinely means fewer tears.

By Stephen V.Updated How we choose
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Dicing an onion is the knife skill you use more than any other, and it's the one most people do awkwardly. The method below is fast, even, and — importantly — safe, built on the pinch grip and claw from how to hold a chef's knife. One thing worth saying up front: a sharp knife makes this both safer and less teary — it slices cleanly instead of crushing the cells that release the eye-stinging gas.

Step by step

How to do it

  1. 01

    Set up safely

    Use a sharp chef's knife on a wood or plastic board that can't slide (put a damp towel under it). Grip the knife with a pinch grip — thumb and forefinger on the blade, not the handle — and keep your other hand in a claw, fingertips curled under and knuckles guiding the blade. A sharp knife is safer here than a dull one, because it doesn't skate off the onion's skin.

  2. 02

    Halve it through the root

    Trim off the top (stem) end. Stand the onion on that flat cut end and slice down through the middle from top through the root, so each half keeps part of the root attached. The root is what holds the layers together while you cut — don't remove it yet.

  3. 03

    Peel and place cut-side down

    Peel off the papery skin (and the first tough layer if it's damaged). Lay each half flat, cut-side down on the board, with the root end pointing away from your knife hand. The flat face gives you a stable base so the onion can't roll.

  4. 04

    Make horizontal cuts (optional, for a finer dice)

    For a fine dice, make one or two horizontal cuts parallel to the board, from the tip toward the root, without cutting all the way through the root. For a standard dice you can skip this step — the layers already give you one dimension of the dice.

  5. 05

    Make vertical cuts toward the root

    Cut down through the onion in a series of parallel vertical slices, again stopping just short of the root so the onion stays held together. Space the cuts as wide as you want your dice — narrow for fine, wider for chunky.

  6. 06

    Slice across to dice

    Now slice crosswise, perpendicular to your vertical cuts, and the onion falls apart into an even dice. Keep your guiding hand in the claw and move it back steadily. When you reach the root, stop — discard the root end rather than chasing the last bit.

Questions

Frequently asked

How do you dice an onion evenly?

Halve it through the root, lay each half cut-side down, make vertical cuts toward (but not through) the root, then slice crosswise. The still-attached root holds the layers together so the cuts stay even and the onion doesn't fall apart until the final crosswise pass.

Does a sharp knife really reduce onion tears?

Yes — a sharp blade slices cleanly through the cells, while a dull one crushes them and releases more of the gas that makes you cry. A keen edge (kept sharp per our sharpening guide) genuinely means fewer tears, plus better safety and cleaner cuts.

Why leave the root on when cutting an onion?

The root holds all the layers together while you make your cuts, so the onion stays stable and dices evenly instead of sliding apart. You cut toward the root but stop short of it, then discard the root end at the end.

What knife is best for cutting onions?

A sharp 8-inch chef's knife is ideal — long enough to slice cleanly, with the control for a fine dice. See our best chef knives for the blade, and keep it sharp for the safest, least-teary cut.

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Sources

We do not run a test kitchen, and we do not pretend to. Specs are the manufacturer's published figures, attributed as such; where we could not verify something, we say so on the page rather than quietly leaving it out. Read our full method.