How to Dice an Onion Quickly and Evenly

This guide is for anyone who hacks at onions slowly, ends up with uneven chunks, or cries every time. You will learn how to hold a knife safely, the classic method for dicing an onion into even pieces, how to change the size of the dice, how to slice and mince, and practical ways to reduce tears. All you need is a sharp knife and a stable chopping board. Knife safety points are general information; take your time while you learn.

Why Even Dicing Matters

Onions are the starting point for a huge number of dishes: soups, sauces, curries, stews, stir-fries and salads. When the pieces are all the same size, they cook at the same rate, so you do not end up with some pieces burnt and others still crunchy. Even dicing also looks better and makes sauces smoother.

Speed comes from technique, not from chopping faster. The chef's method uses the onion's natural layers and its root to hold everything together while you cut, so each cut does more work. Once you learn it, a medium onion takes under a minute.

Choosing the onion helps too. Pick onions that feel firm and heavy for their size, with dry, papery skins and no soft spots, green sprouts or dark mould near the neck. Medium onions, about the size of a tennis ball, are the easiest to learn on: they fit comfortably under your claw hand and have layers thick enough to guide your knife. A very large onion can be halved and then each half cut into two shorter pieces before dicing, which makes it easier to control.

Set Up Safely

• Use a sharp knife. A sharp knife cuts cleanly with little pressure and is less likely to slip on the onion's smooth skin. A blunt knife crushes the onion, releases more of the compounds that make you cry, and is more dangerous.
• Choose the right knife. A chef's knife about 18 to 23 cm (7 to 9 inches) long is ideal. A smaller knife works for small onions and shallots.
• Stop the board sliding. Put a damp cloth or a sheet of damp paper towel under the board.
• Make a flat base. Never cut a round onion that can roll. Every method below starts by creating a flat side to rest on the board.
• Clear space. Keep the area clear of clutter and have a bowl ready for the diced onion and another for the skins.

How to hold the knife: grip the handle with your middle, ring and little fingers, and pinch the blade just in front of the handle between your thumb and the side of your bent index finger. This pinch grip gives far more control than holding the handle alone.

How to hold the onion: use the claw grip. Curl the fingertips of your other hand under, so your knuckles sit forward of your fingertips. Rest the flat side of the blade gently against your knuckles as a guide. Your fingertips stay tucked back and away from the edge. Move the claw back a little after each cut.

Keep the knife flat on the board when you are not using it, with the blade facing away from you, and never try to catch a falling knife; step back and let it drop.