Ask Kenji Live: What is the Best Way to Cut on Onion?

I recently published an article in the New York Times about how to cut an onion in the most consistent, even way possible using a mathematical model. I'm going to show you how to do it live. I'll stick around for a little Q&A afterwards as well.
Here's the article (paywalled):
www.nytimes.co...
Here's one of the models:
www.geogebra.o...
Here's a blog post discussing the onion problem:
/ a-solution-to-the-onio...
Image: Nicolas Ortega for the New York Times

[@dodgeball28]

I was so confused, he looks at least 20 years younger than I remember him from the covid days when I first started following him.. so proud of you Kenji!!

[@979259]

looks like he lost a ton of weight to me

[@richardc9626]

He has. Ozempec is a hell of a drug.

[@terif5198]

@@dodgeball28 me too!! He looks great!

[@NagashiChidorii]

Semalglutides are crazy

[@GrilledTofu]

I remember him talking about the best way to cut onions months / years ago. I’m glad he came back to this with a computer model. How fascinating. Thank you for sharing !

[@R.Akerman-oz1tf]

The finer science of Onion Geometry.

[@GrilledTofu]

I found the video from when he spoke on the model and onions earlier! kzbin.info/www/bejne/mae1gKCFarR3pLMsi=hUsGPX7rc2MDynMg&t=435

[@plotdot32]

I feel like I’ve heard this explanation from him quite a few times - I know because I’ve been thinking about it every single time I cut onions for a long time now.

[@R.Akerman-oz1tf]

@@plotdot32 Yah, Someone mentioned that Yesterday. It's only an Onion; not architecture(he-he).

[@Damalycus]

this explains why I already do it like this. I totally forgot. I was expecting something new, but got some extra validation I guess.

[@skyeline9228]

Using math to optimize the chopping of vegetables, I love it

[@R.Akerman-oz1tf]

So, "leave the root on to hold it together"? (helping hand)

[@johnn26]

damn. kenji working out and getting fit. looking good!

[@MJTripp]

Definitely not that

[@Mateuszyk]

@@MJTrippwhat than?

[@JKenjiLopezAlt]

Thanks. Replaced nightly drinking with nightly exercise and surprisingly it’s made me healthier. 😂

[@Mateuszyk]

@@JKenjiLopezAlt u look great! Keep doing what u do!

[@kaboomkp]

I was gonna say he looks great with the haircut too

[@SteveMorman]

Before this video, I would call my onion cutting "Lazy Radial" and I'm astounded to see that the math supports my half-assed cuts!

[@bannor99]

Laziness is often synonymous with efficiency

[@radiac6818]

Props for using the term "polar coordinates". I majored in Physics in college and got a PhD in engineering, we covered polar coordinates (spherical AND cylindrical) in math class, and used them a lot in electricity and magnetism. Somehow cutting an onion never came up. That said those classes probably induced about as much crying.

[@dirtyketchup]

Dang! Coming in with the fresh cut in addition to all that hard-earned weight loss?! Dude, you have fully emerged from your chrysalis as an absolute inspiration. Having watched your videos from the old kitchen 4 years ago with the late night vids, to the creative force that you are now is amazing! Keep it up, Kenji!

[@GrizzlyAt0ms]

Funny, I think cutting onions was how I first discovered you. The scientific explanations paired with your loose, improvisational approach to cooking is what made me a fan. "But do it however you want" is what makes everyone trust you. Anyway, I've been cutting onions this way ever since. And now you bring the stats to back it up!

[@tylerjohnson3523]

Totally agree! "I practiced this and found it to work well for these reasons. It's cool if that doesn't work in your application." Should be the basis for so much outside of cooking.

[@80neptune]

You are seriously an inspiration! Not only your cooking skills but your physical change from a year ago. My goodness!

[@mikes4357]

I can’t be the only one that gets this warm and fuzzy feeling inside my soul every time Kenji goes nerd?😊

[@m.theresa1385]

Nah .. me too! 🙋‍♀️

[@kewpiefan72]

I have ALWAYS wondered why experts did the horizontal cut! Your new way makes sense, thanks. I have a new way of dicing onions!

[@getthefonyourdot]

I do wonder if the horizontal cut is still superior to getting more consistent dices though. He said the radial slicing is the best out of all the “efficient” and simple slices. I wonder if he bothered to compare them

[@esoteridactyl]

@@getthefonyourdot The model he showed says horizontal slice improves it even further

[@rebelrebel10]

Kenji, you are looking phenomenal these days! Would love to see a video about your recent diet strategy.

[@riuphane]

This is the kind of random crap that most people don't care about, but the fact that you care about it so deeply and evidently is why you are my favorite!

[@TheBClark88]

I clicked on this to check this was actually Kenji - looking great man!

[@stephanieolinger1118]

Here is another approach that should yield similar results but has a few mathematical advantages. Start with a vertical cut in the center. The next cut should end where the outer edge of central ring meets the cutting board. As you make subsequent cuts, each should end at the outer edge of the next ring. With this approach, the correct number of cuts naturally arises from the number of rings in the onion. When considering a quarter of an onion, one must make N cuts including the vertical cut, where N is the number of rings including the central ring. If considering a half of an onion, one must make 2N-1 cuts including the vertical cut. This also means that the radial distance between the starting point of each cut along the outer surface is 90/N. The modeled half onion shown in the diagram starting at ~7:20 has 10 rings, and we would therefore make 19 cuts. Starting from the vertical, each subsequent cut must start at a point 9 degrees along the outer circle from the last cut and end at the boundary between rings as describe above. It should be clear from the diagram that this will give similar results (this method naturally results in 10 cuts for the depicted quarter onion, whereas Kenji's diagram shows 8 cuts). While I believe its relationship to the onion's natural geometry is appealing, I can't say whether the resulting distribution of onion pieces is favorable compared to Kenji's proposed method without a bit of additional work, and my proposed method does require more cuts, so it may be less efficient. However, it removes any confusion about where cuts should be placed, which may be a favorable feature for some.

[@alexsomerslahr8359]

Your MIT chops are on full display! LOVE IT! I'll be showing this to my high school math students at some point (not far from MIT). Thank you!!

[@agnieszkaczerwinska6640]

I’m glad I used to be good at math and figured it out all by myself nearly 30 years ago 😅 I always found the horizontal cut finicky and wanted to avoid doing it. I’ll still sometimes do it if the onion is exceptionally large with very thick layers . Loved the video!

[@theunhappyzombie]

you got proof?

[@frankunderbush]

Okay that geometry math is pretty dope. I still can't help but to remember a comment Kenji made during one of the COVID cooking videos (I'm paraphrasing): When your wife cuts onions a certain way, that's the right way/leave her alone LOL Unrelated, great to see the progress of him getting back in shape! Keep it up my dude!

[@Freelancer.Warzone]

THANK YOU I was (probably still is) extremely against the horizontal cut. I personally always felt that it just de-stabilized the onion unnecessarily, and this is what caused so many cuts in the kitchen.. I have my own way of dicing that is fitting for my hand, but never ever had to use the horizontal cut, and have been preaching vehemently against it. Caught myself arguing with strangers on the internet about the necessity of it, because none of them could come up with an answer that justified it.. goes without mention that I appreciate that it was you, showcased, demonstrated and explain how and when it must be used in what manner to achieve the results that you want! My thanks goes to you, take care and be safe c:

[@wingedcoyote]

Huh, this looks surprisingly close to my usual method of "vertical, but tilt'em just a little bit as you move outward". Happy to see the data!

[@TheTookboy]

Hahaha, that’s exactly how I’d have described my own dicing technique if asked.

[@tannerberry1480]

This may be the most culturally important video you’ve ever made, no hyperbole. This is the kind of information that reserves its own place on the Rosetta Stone. A perfect simulacrum of your style of culinary art: informed, researched, accessible, and drenched in compassion. May we all eat well, and may we thank you for helping us do so ❤️

[@rykwon4535]

I know you really wanted to use the word "simulacrum" today but I'm afraid we've missed the mark here.

[@bushDid911]

I've been doing this for over a year since you first mentioned this concept. Thanks for elaborating on it a bit more in depth, with the horizontal camera demonstration and graphics

[@shiolei]

This demonstration of the 3 cuts helped me better visualize and understand what you meant by aiming for the point below the cutting board. I heard you bring it up in past videos but I wasn't exactly sure what the outside strokes would look like under this video and the diagram. Thank you for this!

[@JamesYorio]

Thank you Kenji for this video. I wrote a comment on one of your videos a while ago to just follow the contour of the onion (the exact way you do here) to get "equal sized" pieces. I was also trained the classic way in school and thought it not right, especially when French cuisine is so particular about everything.

[@HasXXXInCrocs]

You look awesome kenji, it's clear you've been taking care of yourself age the work is paying off!

[@_SurferGeek_]

Good to know that my sloppy attempt at radial cuts approximates your 60% method! I'm actually happy now for being what I thought was a bit lazy. 😁 Have you noticed that onions that you grow vs. onions from a grocer differ in that the grocer cleans the onions up by peeling the very loose outer layers. I feel this is done for a "prettier" product and it's possible this is done as part of the processing prior to the grocer getting them. I've found more moldy, green onions over the last 15 years or so and that's the only reason I can think of.

[@jeffreykennedy5956]

First chef to explain horizontal cut.

[@cyranthus]

I always thought it was kind of pointless since the onion is already divided into layers anyways, but I never thought about the angle thing.

[@KLucero22]

The amount of contributions Kenji has made to the culinary community is difficult to count. But this one may be the most wide-reaching and universal one yet. I imagine many chefs across multiple cuisines will adopt this method moving forward

[@cashmeregrandma8331]

Thank you so much. I've been searching and searching for this method. I knew there was a way to do it without the horizontal cut.

[@Ahkuji]

Can we talk about this transformation you’ve made?! Great work my man!

[@workaholica]

That's how I have been cutting onions for a while, because the radial cut seemed too extreme to me. Many thanks for the mathematical proof.

[@ixfalia]

I'm surprised, but this is the way I've been cutting onions for many many years. For much of my college years I didn't have nice sharp knives, nor good knife skills, so the horizontal cut ended up being just prohibitive. So I started angling the radial cuts as if the center was beneath the surface of the cutting board. It really helps make more even pieces. I love onions in my food but until I did it this way I despised cutting them lol

[@kennyjac]

Been proselytizing with this as much as possible for years! Also at first i thought this was and old video because Kenji looks so much younger wth 🤯

[@mth32871]

As someone who has always loved math, I absolutely LOVED all the math terminology and analysis that you did - just to find the best way to cut an onion! Having said that, I don't know that I care enough if my onion pieces are consistently sized, but I will certainly give it a try the next time that I do have to cut an onion. And if I find myself crying, it will be because of the joy of combining cooking and math. 🙂

[@fifzeppelin]

It'd be fun to see a graph of piece size distribution for a given number of cuts as that focal point moves from the center, down to the 60%, and eventually approaching infinity (which would be the same as the vertical slicing).

[@stylisgames]

I finally get the purpose of the horizontal slice method! Thanks Kenji! That said, I'm using the Kenji method from now on 😎

[@mimic5653]

When I read that Kenji went to MIT in his book I was not surprised. He’s just so smart it oozes out in his cooking and the way he explains everything in a scientific way.

[@fmaleknia]

Incredible method, love it. It came to my mind, that how much we take imaginary optimum point down is kinda related to how many layer we have in the radius span..

[@coreyduval3171]

Something to think about is the inaccuracy of most home chefs' cuts. I would not be surprised if many home cuts end up more like the offcenter Radial cuts when they think that they are really doing perfect radial cuts. It's a natural mistake to make.

[@MAKEITSF]

This is probably the most thorough explanation of cutting an onion. Well done!

[@middlelb21]

Hi Kenji, the 60% radial cut method is also the method Martin Yan has used for as long as I can remember.

[@mrmojorisingii]

Kenji's real mathematical genius is somehow dividing an onion into three halves! Nice magic trick!

[@stillTK]

Just wanted to say, you’re looking good Kenji! Keep it up!

[@bryguy102]

This is such an interesting question with regards to optimizing onions. I wonder if it could be optimized easier or further by separating the inner concentric onions from the outer and treating them differently. I’d also be curious how the expected distribution of sizes would compare to real world. It sounds harder to hit that 60 degree angle, but I suspect it’s pretty forgiving. Fully concentric sounds way harder, but straight down is indeed easier. Maybe slapchop is the real answer?

[@sabingratz]

Thanks Kenji, this is awesome. What if you want a finer dice? Any tips on additional steps to this method to get smaller segments? Thanks.

[@fredturnerf]

I've done this since Kenji originally posted the concept on Serious Eats many years ago. I'm glad it's getting the attention it deserves!

[@CptVein]

Damn Ken! Looking lean!

[@Mach1Greeble]

I thought it was a 15 year old video.

[@jordanl5341]

He's getting divorced he's been hitting the gym

[@Jkizzle4996]

@@jordanl5341damn wtf

[@linds7774]

@@jordanl5341no he’s not. Stop it.

[@bushDid911]

​@@jordanl5341 Completely delusional and unbased claims such as yours add nothing but engagement for creators. The divorce rumors were started because of his vaguely captioned instagram post of what looked to be an apartment, which we now know was the beginning of his move into his current house-boat. I sincerely hope someday you grow up and integrate into adult society where people don't spread false rumors in the name of childish, juvenile thrill.

[@polythewicked]

Hey, that’s exactly how I cut mine - the 60% model. Not intentionally, I just have a hard time cutting a perfect radial lol

[@lucasl1470]

Based

[@tiarkrezar]

Honestly, if I want fine dice I just use the traditional method, it seems a lot quicker and less fussy with the positioning of your knife. However, if I'm making a stew or something where I want to retain more texture and keep it in thicker slices, I've been using a similar "pseudo-radial" method, it works out rather well.

[@okonomiyakipizza]

Oh wow, I did not expect to find someone I know in comments of a new Kenji video 😀 Hope you are doing well L, you are often on my mind.

[@MerrickOffTopic]

Thank you for reposting this polished version, Kenji!

[@_SurferGeek_]

I see what you did there... 😅

[@swit1905]

Another question for your wonderful Ask Kenji series: Is it really best to gently simmer bones/aromatics for stock rather than a rolling boil, or is that just a myth? If simmering is best, why?

[@macaoron]

I’ve recently started cutting horizontally from the base until halfway to two-thirds of the way, then do vertical cuts on the unsliced center portion and cross cuts, which seems to be faster but still relatively uniform like the traditional way. I’ll have to give this 60% method a go! Also, love the nails!!

[@AllHandlesTaken91]

I love how Kenji shows us how he's the greatest with mathematical proof. I will now go forth and divide and subdivide every onion I come across. Not quite vertically, not quite radially.

[@paulmeadows6386]

Haircut looking really good man it suits you way better than long hair.

[@themultigrainmuffin]

Gems: "an onion can be approximated as a cylinder" and (talking about the central radial cut method) "slices get infinitely thin towards the center". I love it. Just like being back at school.

[@dylansands8651]

Kenji and Onions, 2 of my favorite things!! Thank you for the incredibly informative and concise explanation❤ The debate should finally be settled with this conclusive evidence…

[@Moley1Moleo]

I was surprised when you said the radial cuts were bad, because I'd had great success with them. Turns out, I lacked the precision to actually aim for the true centre, and my approximation of going *towards* the centre, but still aiing for a spot on the board to avoid risking cutting myself with crazy angles, actually comes close to approximating the optimal method you arrived at!

[@_fellow_]

Dude you look 10 years younger in this video. Nice work with whatever changes youve been making!

[@dirtyketchup]

On a slightly more analytical note, I wonder if this method has a scaling issue. One of the nice things about the traditional method is that, due to the perpendicularity of all the cuts, it's very simple to change the dicing size that you're after. Is there a limit with Kenji's modified radial method that starts to have diminishing returns in evenness when the cuts are wider or narrower, especially towards the outer edges? Obviously one of the immovable variables is the thickness of the onion layers themselves, and it makes me wondering if this modified radial cut technique only works within a specific window of the ratio between the thickness of the layers and the thickness of the cuts. That supposition aside, I do really enjoy the mathematical proof surrounding this technique as well as the explorative exercise behind it all, but I still just don't think I'll be able to get behind it in a practical sense. There's just something about slicing an item with cut angles of continuously changing degrees that makes me uneasy, both from a constancy standpoint as well as safety. Maybe it's my autistic nature and love of repeatability coming out, but I think that I'll be able to achieve more consistent results by using the simplest method, and I also worry that trying to relearn a method that has my knife hand constantly adjusting chopping angle against my guide hand could lead to higher risk of injury. And if I just slow way down to perform the cuts like he did in the demonstration, then that kind of defeats the purpose of the "efficiency" in the method; fewer cuts isn't more efficient if the fewer cuts are also slower cuts, and add into that the additional complication of changing angles, and it just sort of makes me feel iffy about it. I don't know, that's just a gut reaction. I still probably need to at least try it out on a few onions to actually come to a real personal conclusion, but those are just my initial 2¢. At any rate Kenji, thank you for always pushing us to stretch our minds and challenge ourselves. Keep up the awesome stuff!

[@bigbird2451]

That take off the first white layer of onion trick is something that I figured out on my own at my first kitchen job where ten gallons of onions was just the start of my shift.

[@JacksonBockus]

Interesting. We can treat vertical slicing as a radial slice with an offset of -infinity, and radial slicing has an offset of 0. The vertical method provides a good minimum size but the maximum is too high. The radial method caps the maximum well but the minimum is very small. So it makes sense that the ideal will lie somewhere between 0 and negative infinity.

[@ferdinandbraun8794]

I think I intuitively drifted toward cutting onions in your modeled way just because its the easiest way to cut it up

[@Joe_Murphy-REV_Realty]

You are one brilliant chef, Kenji!! Thank you.

[@timstalam]

The 3D modeled onion to determine this cutting method is mad scientist levels of insane. I am going to start cutting onions this way now.

[@frederickheard2022]

It was definitely a 2-D model.

[@Kazathur]

Another case for Inspector Golden Ratio :D. Love it when math flows everywhere. Thank you for the video

[@HaakonLynvingen]

I really enjoy these nerdy food vids, never stop bigboss!

[@Pixin25]

Is the vertical cuts standard deviation computed using the horizontal cut or only the vertical ones ? I'd be interested in finding out about the difference in both case.

[@kimba341]

Fantastic video! I've watched video after video but always forget what I saw because it was so fast. But what I want to know is why you weren't crying!!!

[@Mostlymattie]

Kenji looks like you’ve turned back the hand of time by 10 years 😃 good work you👏👏

[@JavierBonnemaison]

I also always take off the first two layers, as the second layer is a transition layer between the papery skin and the succulent inner layers.

[@MrJiggerify]

does the optimal method only hold true for the first cut into the onion half or does it account for the changing shape as you move through it?

[@Dr_DNoir]

Just leaving a comment to support the channel. As always: love the scientific approach.❤

[@twrob82]

I certainly appreciate this video as a mathematical solution to a vegetable-prep puzzle, but I'm wondering if there's any reason why it would be important in a professional kitchen to minimize the standard deviation in the size of diced onion pieces. In other words, does it make any difference in the cost of doing business (cost of ingredients, personnel, rent, utilities, etc.) or in the flavor, visual appeal, or eating experience of a dish?

[@richardschneider9098]

Good science! Or math, as the case may be. When I feel cocky and have a cooperative onion & knife, I'll cut only 3 offset radials (the last method) all the way through. In between those, I come back and cut only 1/2-2/3 of the way down, 2x per segment, then just crosscut as usual. tbh I don't know if it's any more effective, and often I think I have found the point of diminshing returns on effort.

[@veraxis9961]

Awesome! But I have a question: what is the effect of the horizontal cut in your mathematical model? It looks like the "vertical cuts" model does not include it, so how much does the horizontal cut change the standard deviation? Is their an optimal height for the horizontal cut? I would guess somewhere between 1-2 layer-widths up just eyeballing it.

[@Edgeinx]

Holy cow this is the same kenji? Whole new man.

[@kaibuchan]

One of the most important cooking videos ever.

[@anne1k616]

Kenji, how can I get my knives crazy sharp like yours? It makes a huge difference for slicing onions.

[@alextopfer1068]

What's doing it is probably that his knife is quite thin behind the edge (like 3mm, 1/8th up from the edge). A thin blade wedges the onion apart less, think of a wood axe vs a scalpel. A lot of cheap knives are overly thick there, because it's easier to make. So if you can investing in a nice thin knife may help, a large petty or a small chef's knife of some type. For the actual sharpening i like whetstones, but that is a skill you need to learn.

[@AmirhoseinHerandy]

Also he has said that he has a lot of knives that he sharpens like once a year amd goes through them throughout the year, changing to a different one when the last one starts feeling dull.

[@infoscholar5221]

Kenji has been pondering this for years, I remember him discussing it while cooking, perhaps it was during the Big P.

[@jomicheleseidl2033]

First impression: Wow, Kenji, you look so handsome in your yellow apron and a new haircut? Anyway, had to get that out of my system. I'm looking forward to trying this method. I'm not a super precise cook but I do appreciate making uniform-sized pieces that will cook evenly or absorb flavors evenly like when you're pickling. Nice to see you working in the new kitchen.

[@DGDfan13]

Thanks for this Kenji!

[@ryana6494]

How different is 60% from 100% in terms of standard deviation??? Aiming for the imaginary other side of the onion would be an easy thing to remember and might yield similar results! I’ve followed this method loosely for years but couldn’t have told you that it was a 60% rule. Thanks for the great videos, Kenji!

[@zindobd]

First of all you are looking really healthy! Great video, as always. I like how there is a lot of light in your new houseboat kitchen, and I am really looking forward to new content. What knife are you using?

[@stianaslaksen5799]

One method you did not mention is tearing off all the layers and stacking them on top of each other and holding them flat. With that method you can get as small squares as you want.

[@3xarch]

kenji is the only person who's managed to actually explain properly why horizontal cuts happen in the traditional method

[@janem3575]

wow. fantastic video! love the detailed visual. really helped a lot!

[@JavierBonnemaison]

That's how I do it. Cutting radially is intuitive because the onion has those lines on it already and you can use them as a guide, but clearly cutting towards the center results in triangular sections rather than trapezoidal. in simple terms they are too thin at the bottom. I got there with a mixture of intuition and trial and error, but it feels great to be vindicated with some more rigorous analysis.

[@plotdot32]

Kenji, you look so happy and healthy. This stranger is really proud of you for getting sober. One day at the time!

[@Dad_Lyon]

I'm an engineer, and basically have been doing that modified radial method for the last couple years. Neat.

[@craigsmith3741]

kenji taaught us this years ago and I've been using it ever since

[@danpickard3258]

The most important aspect of cutting an onion (and with less crying) is... to use a very sharp knife. :) If I had to choose between a dull chef's knife and a sharp paring knife I would choose the paring knife. I do often use my nakiri however.

[@lilxerath5881]

Been warching you since ur night snack videos u are the best keep it going you rock!!

[@ZeroTwoDarlingXO]

Mirin’ brah! Man i gotta get into shape too. This is my sign!

[@Aio-Project]

never thought id hear about polar coordinates in a cooking video but my math brain is very satisfied

[@DeeDeeSanchez3]

I've found the same but I cut the half moons then the radial cuts. It takes a little coordination to hold it together but it works. Pieces are more uniform which I like for Pico de Gallo.

[@rsts32]

Geez Kenji awesome video but also you look great!! Props to you!

[@wozzinator]

Aiming for the radial 60% below the center feels challenging so I’m wondering if instead of cutting the onion in half you cut it at the 60% radial instead? Awesome analysis regardless!

[@davecowan4174]

Love this video. I have been a follower since I first saw you on The Chew promoting The Food Lab. I remember a previous onion video about cutting an onion to minimize the release of fumes which can cause the eyes to water. Unfortunately, I can't remember that trick. Wish you had mentioned it in this video.

[@usafmd1]

Looking great, Kenji. What are you doing to lose all the weight and get trim?

[@SamSam-qm1li]

I love this guy. He uses science for better cooking techniques

[@epona9166]

The smallest standard deviation between the largest piece and the smallest piece. LOL. You're my guy!!