The Absolute Best Way to Dice an Onion, According to a Chef

Follow these no-fuss steps.

January  9, 2019

If you’re brainstorming what to make for dinner, then dicing an onion is never a bad place to start. It's the Goldilocks zone in the onion world: bigger than a mince, smaller than a chop. And it’s a wonderful building block of so many meals: soups, stews, salads, sauces, and stir-fries. Which means, by the time you’ve finished, you’re already well on your way to a spectacular dish.

But with all that riding on an onion, you want to do it right. Which is why we’ve asked Test Kitchen Director Josh Cohen to teach us the hands down absolute best way to slice and dice an onion (without shedding a tear!). Here’s how:

1. Sharpen up.

If you'd rather not cry into your perfectly diced alliums, then grab the sharpest knife you've got. "If you imagine the onion cells on a microscopic level, then a dull knife is like smashing through them with a hammer, crushing the cell walls and releasing vapor," Josh says. "If a knife is sharp, it slices through these cells cleanly." In other words, it's time to show your knife some TLC. Looking for a guide? Head here.

2. Stick to the root of the matter.

The root of the onion keeps everything together—if you cut off too much of the root, your slices will fall apart as you dice. “The trick is to just barely trim the root end, so that you can still see that opaque circle,” Josh says. “It’ll make your job much easier.”

Photo by Me

3. Peel and prep.

Next, halve the onion through the root and tail ends. Chop off that tail end and discard, then remove all traces of papery skin. Depending on how fresh your onion is, you might want to peel off the first layer as well. "It can taste papery to me," Josh tells me, "but that's just a weird personal preference."

4. Finally, cut up!

Okay, here's where Josh takes a swerve from the customary culinary-school rules. Typically, you'd make two to three horizontal cuts through the onion, stopping before you reach the root to ensure evenly square pieces of onion.

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Top Comment:
“I’m always trying to work on my knife skills! I think a video would be very helpful here, plus they are always so beautifully done!”
— alexis

"Maybe if you work at a really detail-oriented kitchen, it'd matter," he says. "But it's just an extra step that I don't think you need. My method looks pretty much the same."

In Josh's method, position the onion so that the root end is facing away from you, then cut vertically into the onion, stopping about four-fifths of the way through. According to Josh, "the root of the onion should still be holding everything together."

Cut about 80 percent of the way through. Photo by Me

5. Take it home!

From here, it's the slicing you know and love. Starting at the tail and moving toward the root, cut across the onion to make tiny, evenly-sized pieces of onion.

Voilà! No mess, no falling apart—and you're on your way to dinner.

For more onion tricks...

Do you have any tips for chopping onions? Tell us in the comments below!

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See what other Food52 readers are saying.

  • Heybob
  • MBE
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Katie is a food writer and editor who loves cheesy puns and cheesy cheese.


Heybob May 18, 2020
A video would’ve been nice.
MBE January 16, 2019
Also a fan of this method! The only thing learned to do differently is to angle the vertical cuts following natural arc curve of the onion. The resulting dice are very even in size.
msmely January 20, 2019
This is the method I've used for years and endorse!
Bonus points if you flip over the tail end for some extra bonus small cuts that lower the amount of wasted onion. (Unless you like saving onion bums for soup.)
Bob L. January 13, 2019
What I’ve never liked about this method is the horizontal cuts after the vertical cuts which seem dangerous and then you have the leftover portion of the onion that wasn’t diced. My method is simply to slice half of an onion horizontally in 1/8 to 1/4 inch slices and keeping the slices in place as you draw your knife out. Once all sliced and neatly in place, you turn the onion a quarter turn so the slices are in top to root position and make cuts through the onion perpendicular to the round face of the onion. As your perpendicular slices get past half of the onion, you are left with a smaller portion of the onion which is harder to stabilize and at that point, you allow face of the onion you are cutting on to fall forward on the cutting board and continue your perpendicular cuts until you have a fully chopped onion with no waste. So much simpler!
kantcould January 13, 2019
I do it similarly to Bob L. but using the earth as an analog helps the description. The root end is the south pole and the tail end the north pole. Cut the onion in half, pole to pole. Lay the hemispheres flat and turn so that you are facing east to west in line with the equator. Make slices parallel to the equator, spaced the width you would like your your dices to end up. Then turn the half onion back to the north/south orientation and cut with similar spacing across the other cuts and, voila', the half onion should fall apart into a nice dice. In making the first set of cuts, it helps if you leave an uncut strip at the edge to hold the slices together for the second cut. Repeat with the other half.
mdelgatty May 28, 2020
Not following you; using the method described there are no horizontal cuts..
Bob L. May 28, 2020
The horizontal cuts are those made parallel to the equator in Josh's description.
alexis January 11, 2019
I’m always trying to work on my knife skills! I think a video would be very helpful here, plus they are always so beautifully done!
Rick January 9, 2019
If you plan to sauté those onions, pour a bit of oil over the onions first. Keeps down some of the juice spray
And when you're done, you can remove the onion smell from your fingers by rubbing them with a wet stainless spoon. Don't know why but it works!
Laura January 9, 2019
I unfortunately am math dumb !!
When you say an eighth or 5/8 or horizontally and vertically my eyes glaze over a short video would be more helpful, thanks
Leaseachef January 9, 2019
"In Josh's method, position the onion so that the root end is facing away from you, then cut horizontally into the onion, . . ." Don't you mean vertically? You just explained that he's NOT advising cutting horizontally unless you are working in a very particular kitchen. Also, the photo shows vertical cuts.