How to Cut an Onion (Chop, Dice, Mince, and Slice!)

Close-up of sliced, chopped, diced, and minced red onion in a big pile from top to bottom.

Share this post:

This tutorial on how to cut an onion will improve your knife skills! We’ll teach you how to dice, chop, slice, and mince easily without tears.

The number of savory recipes that start with dicing up a simple onion is incredible! You can add so much rich, layered flavor to your dinner just by whipping out a knife and a cutting board. In soups, in sauces, in salads, on sandwiches—onions are the king of the kitchen!

But if you’ve never cut an onion before, those guys can be intimidating! How do you peel them? How do you slice them? And how in the world do you cut them without crying? No worries, we’ve got you covered! We’re tackling everything you ever wanted to know about cutting onions today.

Overhead of hands holding a large white ramekin of chopped red onion.

Why does cutting onions make us cry?

Let’s talk about the elephant in the room—cutting onions can be painful! When you cut into an onion, each cut breaks open tons of onion cells, and their juices are released. Enzymes and sulfur-rich amino acids swirl together and form a chemical reaction, which creates a chemical called syn-propanethial-S-oxide. This volatile chemical easily vaporizes, which means it floats up into the air, comes in contact with your eyeballs, and OUCH. Your brain signals your eyes to start watering to try to protect themselves from the irritant.

Wholefully Protip

Those of us who wear glasses get the worst of it when it comes to onion tears because the pocket of air between our glasses and eyeballs holds onto the fumes longer. Remove your glasses (if you can still see!) while cutting onions or wear contacts for the least pain.

Chopped red onion in a pile with minced red onion in a pile behind.

Which onions make you cry the most?

Because of the chemical reaction, the onions that cause the least tears are those with lower sulfur content. Sulfur is what causes the “bite” in onions, so in general, milder, sweeter onions (like Vidalia, Walla Walla, etc.) will cause less eye irritation. Non-sweet yellow and white onions tend to be the worst culprits for tears.

What’s the difference between diced, minced, chopped, and sliced onions?

Okay, here’s your onion glossary so the next time you go to cook from a recipe, you know exactly what kind of cut to do:

Overhead of four piles of red onions, labeled from top to bottom: minced, diced, chopped, and sliced.

  • Minced onions: Minced is the smallest cut, in which onions are cut into very fine pieces.
  • Diced onions: This is the most common cut, and it’s when onions are cut into medium-sized chunks.
  • Chopped onions: This is a bit larger than diced onions.
  • Sliced onions: These are either whole or half slices of the onion.

What knife do you use to cut onions?

A sharp knife is key to not only getting good, even cuts, but also to help prevent tears! Sharper cuts mean fewer onion cells are broken open, which results in less of the irritating gas being released

A large, sharp chef’s knife is the best option size-wise, because it allows you to get good leverage and cut the onion in a series of single cuts. This is not the time for a small paring knife!

Should you wash onions before cutting?

Most folks do not wash onions before cutting. The papery skin of the onion acts as a protective peel .

Overhead of small piles of minced, diced, chopped, and sliced red onion laid out from left to right.

How do you cut onions without crying?

It’s hard to guarantee a tear-free onion cutting session, but we do have some tricks that can help you make the tears less debilitating.

  • Use sweeter varieties of onions like Walla Walla or Vidalia.
  • Make sure to use a very sharp knife.
  • Remove your glasses (if possible) before cutting. If not, you can get ski goggles to go over your glasses. Trust us, it works!
  • Invest in a pair of onion goggles.
  • Freeze the onion for 5-10 minutes before you cut into it. The chilling helps reduce the release of the irritating gas.
  • Keep the root end of the onion intact.
  • If all else fails, invest in a high-quality chopper and cut that way!

Overhead of long rows of minced, diced, chopped, and sliced red onions laid out from top to bottom.

How do you chop an onion?

A chop is the first cut we’ll teach you. Chopped onions are typically larger pieces that can be used in soups, broths, and stews. You’ll often see recipes asking for a “rough chop”—that just means that the pieces don’t really need to be even for the recipe.

Collage of six steps for how to chop an onion.

  1. Slice an onion in half.
  2. Place one half, cut side down, on the cutting board, and then use the knife to cut off the stem end of the onion.
  3. Using your fingers, peel off the outer layer of the onion skin, and discard (save it for making broth!).
  4. Place the onion flat-side down again, and then cut parallel cuts from the root end to the cut end, spaced about 1/2″ apart.
  5. Cutting perpendicular to the first cuts, cut every 1/2″ or so.
  6. Use your hands to break apart the onion layers, if desired.

Wholefully Protip

When holding the onion for cutting, do it with curled fingers or your knuckles. This keeps your fingers out of the way of the knife.

How do you dice an onion?

Diced onion is the way so many recipes start—you really need to get this basic knife skill down if you are going to be cooking often. Sometimes you’ll see recipes list “small dice” or “medium dice”—that’s just an indicator of how large the chunks of onion should be when finished. This is the exact same process as the chopped onion, your cuts are just closer together.

Collage of six steps for how to dice an onion.

  1. Slice an onion in half.
  2. Place one half, cut side down, on the cutting board, and then use the knife to cut off the stem end of the onion.
  3. Using your fingers, peel off the outer layer of the onion skin, and discard (save it for making broth!).
  4. Place the onion flat-side down again, and then cut parallel cuts from the root end to the cut end, spaced about 1/4″ apart.
  5. Cutting perpendicular to the first cuts, cut every 1/4″ or so.
  6. Use your hands to break apart the onion layers, if desired.

How do you mince an onion?

Minced onions are very small pieces. This is typically a cut you’ll use when the onion isn’t being cooked—like in salsas or salad dressings. This allows you to get onion flavor in a bite without having so much onion it’s overwhelming.

Collage of four steps for how to mince an onion.

  1. Do a small dice on your onion.
  2. Place all the onion pieces on the cutting board.
  3. Rock the knife back and forth, going over the onion pile many times to make small, uniform pieces.
  4. It can take a number of passes to get a small mince.

How do you slice an onion?

Sliced onions are one of the easiest to do! Onion slices are often used in pickles and onion sandwiches. You’ll see some recipes call for “thin” or “thick” slices—this is an indicator of how close your cuts need to be.

Collage of five steps for how to slice an onion.

  1. Slice an onion in half.
  2. Place one half, cut side down, on the cutting board, and then use the knife to cut off the stem end of the onion.
  3. Using your fingers, peel off the outer layer of the onion skin, and discard (save it for making broth!).
  4. Place the onion flat-side down again, and then cut parallel to the root end of the onion in even slices.
  5. Make your cuts close together for thin slices, or further apart for thicker slices.

How do you store cut onions?

Cut onions store well in an airtight container in the fridge—you can easily get 7-10 days out of them. Pre-chopping onions is a great way to save time.

Can you store half an onion?

Only need half an onion? No problem. Take the other half of the onion and pop it into a wide-mouth canning jar, zip-top bag, or wrap it up using an onion keeper.  The half of onion will stay good in the fridge for 7-10 days.

Close-up of a pile of chopped red onion on a white marble countertop.
It might feel awkward the first time you go to dice an onion, but the most important thing to remember with knife skills is that practice makes perfect! The more you cook and cut onions, the better your muscle memory will become, and you’ll soon be whipping through onions in no time flat.

Cassie is the founder and CEO of Wholefully. She's a home cook and wellness junkie with a love of all things healthy living. She lives on a small hobby farm in Southern Indiana with her husband, daughter, two dogs, two cats, and 15 chickens.
Starter Guide

The free Living Wholefully Starter Guide is packed full of tips, tricks, recipes, and a 14-day meal plan to get you started on the road to vibrant health.

Meet Cassie
Meet Your Host

Hello. My name is Cassie, and I’m a healthy home cooking expert.

I'm a Certified Holistic Nutritionist, and I've been developing healthy recipes professionally for over 15 years. Food is my love language, and my kitchen tips and nourishing recipes are my love letter to you!

Learn More About Me →