Adidas Ultra Boost Size Chart + UltraBoost 21 Review


This is the Adidas Ultra Boost size chart for men and women in 2021.

Every year, Adidas drops another Ultra Boost silhouette, and every year, it seems to get just a little bit more Boost.

With the 21st iteration, it looks like Adidas went crazy with Boost.

Without further ado, let’s get right into the size chart…

Adidas Ultra Boost Size Chart

Men’s Ultra Boost Size Chart

US Size
Heel – Toe
in Inches
Heel – Toe
in cm
48.7″22.1 cm3.536220
4.58.9″22.5 cm436 2/3 *225
59.0″22.9 cm4.537 1/3 *230
5.59.2″23.3 cm538235
69.4″23.8 cm5.538 2/3 *240
6.59.5″24.2 cm639 1/3 *245
79.7″24.6 cm6.540250
7.59.8″25.0 cm740 2/3 *255
810.0″25.5 cm7.541 1/3 *260
8.510.2″25.9 cm842265
910.4″26.3 cm8.542 2/3 *270
9.510.5″26.7 cm943 1/3 *275
1010.7″27.1 cm9.544280
10.510.9″27.6 cm1044 2/3 *285
1111.0″28.0 cm10.545 1/3 *290
11.511.2″28.4 cm1146295
1211.3″28.8 cm11.546 2/3 *300
12.511.5″29.3 cm1247 1/3 *305
1311.7″29.7 cm12.548310
13.511.9″30.1 cm1348 2/3 *315
1412.0″30.5 cm13.549 1/3 *320
14.512.2″31.0 cm1450325
1512.4″31.4 cm14.550 2/3 *
1612.7″31.8 cm1551 1/3 *
1713.0″32.6 cm1552 2/3 *
1813.3″33.5 cm1753 1/3 *
1913.7″34.3 cm1854 2/3 *
2014.0″35.2 cm1955 2/3 *

Women’s Ultra Boost Size Chart

US Size
Heel – Toe
in Inches
Heel – Toe
in cm
58.7″22.1 cm3.536220
5.58.9″22.5 cm436 2/3 *225
69.0″22.9 cm4.537 1/3 *230
6.59.2″23.3 cm538235
79.4″23.8 cm5.538 2/3 *240
7.59.5″24.2 cm639 1/3 *245
89.7″24.6 cm6.540250
8.59.8″25.0 cm740 2/3 *255
910.0″25.5 cm7.541 1/3 *260
9.510.2″25.9 cm842265
1010.4″26.3 cm8.542 2/3 *270
10.510.5″26.7 cm943 1/3 *275
1110.7″27.1 cm9.544280
11.510.9″27.6 cm1044 2/3 *285
1211.0″28.0 cm10.545 1/3 *290
12.511.2″28.4 cm1146295
1311.3″28.8 cm11.546 2/3 *300
13.511.5″29.3 cm1247 1/3 *305
1411.7″29.7 cm12.548310
14.511.9″30.1 cm1348 2/3 *315
1512.0″30.5 cm13.549 1/3 *320
15.512.2″31.0 cm1450325

Do Ultraboost Run Small?

Generally, the Ultraboost OG sizing is true to size. So for most people, trust your measured size and go true to size. However, for those with wider feet, it is recommended to go half a size up for better comfort.

Adidas Ultra Boost Review


Starting things off, the Adidas Ultra Boost 21 officially released on January 28th and February 4th, 2021.

The UltraBoost 21 replaces last year’s UltraBoost 20 and sits alongside the UltraBoost DNA which is kind of their legacy model.


The retail price for the Ultra Boost 21 is the same that’s it’s been for the last couple of Ultra Boost sneakers and that’s $180.

I think it’s fair to say that the Ultra Boost always has been positioned as a premium running sneaker. When I first saw images of the Ultra Boost 21, I was floored by the amount of Boost it looks like it has in the heel. (pic 1.38)

It really looks like it has by far the most Boost that they’ve ever put in an Ultra Boost sneaker. While that is true, there is some caveats to that.

But the real question that a lot of you all have is how comfortable is the UltraBoost 21 sneaker and is it good for performance running?

Let’s find out…

Related: Puma vs Adidas

Sizing & Fit

So, do the Adidas UltraBoost run small, big, or true to size?

As far as sizing and fit, I have narrow feet and the UltraBoost 21 does run true to size.

If you have wider feet, it might not hurt to go up half a size. However, if you own any of the previous 19 or 20s, the fit is very similar to those.

But at the end of the day, the best way to know if a shoe fits is just to try it on before you buy it.

Here’s the ultimate Yeezy sizing guide of all the Yeezy models released so far. Make sure you check it out.

Performance Running

As far as performance running is concerned, the UltraBoost 21 is still definitely a neutral running sneaker. However, it does have a lot of cushion under your foot.

So, if you’re looking for a very heavily cushioned running shoe that’s still very responsive, the UltraBoost 21 is a great way to go.

Comfort aside, I love the way that this Boost midsole is sculpted. Yes, I don’t love the fact that it’s kind of lying to you about how much Boost is underfoot, but I do really love the way that it’s shaped.

It looks fast, it looks speedy, and it looks is going to bounce you over any obstacle that gets in your way. I especially love the speed lines that are pressed into the middle of the midsole and I feel like they give this shoe a lot of character.

Adidas Ultra Boost 21 vs Ultra Boost 20

Right off the bat, you can see that there are some pretty dramatic changes between the newest model and the previous model.

Related: Alexander McQueen Size Chart


It looks like Adidas is making the Ultra Boost 21 a much more apparent performance model and separating it from the sort of lifestyle aesthetic the 20 and 19 had.

I know the 20 and the 19 definitely look a lot more performance and running-driven than any of the previous UltraBoosts and they kind of lost that cool lifestyle aesthetic that the older UltraBoost had.

But it’s become very obvious with the UltraBoost 21 that the Ultra Boost line is now headed fully towards performance aesthetics.

Honestly, I kind of feel that that’s a good thing because the 19 and the 20 didn’t really seem to fit in any categories visually.

They didn’t look as good as the other lifestyle UltraBoosts and they didn’t really have that sort of aggressive performance look that some other running shoes have.

So, I think whether you like the new design direction of the UltraBoost or you don’t, I think it’s the right move for Adidas. This really gives the Ultra Boost line a lane and makes this shoe look like what it’s supposed to be.

If you had to guess what this sneaker was from just looking at it, I think you would understand the idea that they’re trying to communicate which is an aggressive running performance shoe.

Primeknit vs PrimeBlue


Aside from the overall shape and silhouette change, the UltraBoost 21 does have some notable performance improvements that have to do with materials and new design details.

Diving into some of those details, around the toe of the sneaker, you’ll notice that Adidas is using a brand-new knit material called PrimeBlue.

PrimeBlue is the new version of Adidas’ Primeknit that utilizes primarily recycled materials like the Parley Ocean plastics.

What I really like about this new PrimeBlue upper on the Ultra Boost 21, in particular, is that because they made it a little bit thicker than the previous PrimeKnit, it really contains your foot very well and keeps your foot in place and locked in so that you have no slipping issues.

That seems to be the case even without actually tying the laces. Even if you wear this shoe unlaced for just lifestyle wear, you’re not going to have any issues whatsoever.

Of course, being a brand-new Ultra Boost silhouette, you do have a new knit pattern which seems to be similar to previous UltraBoost sneakers except it kind of extends all the way up to the midfoot of the sneaker.

Around the edges of the ventilation holes, you have these heat-pressed details to add a little bit more structure and aesthetics as well.

Now let’s move to the part of the UltraBoost 21 that I think most people are interested in…

Related: Mizuno Running Shoe Size Chart



According to Adidas, the UltraBoost 21 has 6% more Boost than the UltraBoosts 20. If you look at them back-to-back, it really looks there’s significantly more Boost in the 21 than in the 20. Unfortunately, it’s kind of visually deceiving.

While there is more Boost in the UltraBoost 21 over the 20 and significantly more Boost than the UltraBoost DNA, a lot of the Boost looks like it’s under your foot, but it really isn’t.

On the heel of the 21, it looks like your foot is on top of an inch and a half of Boost, which is obviously a crazy amount. However, there are two reasons why this Boost looks a lot thicker and a lot more plush than it actually is.

The first is that the heel of the shoe actually has a pretty significant curve upward which, to be honest, is really great for running because it makes your movements a lot more smooth.

The second and the most disappointing reason is that your foot actually rests deeper into the shoe than you would expect.

When I first tried the 21, I was expecting mind-blowing levels of Boost. I was expecting my foot to feel like it was just bouncing on top of a cloud. It still feels great and still feels Boost, but it doesn’t feel that much more Boosty than really any other UltraBoosts.

Visually Deceiving

The reason for that is because when your foot actually goes into the shoe, the Boost in the heel is just cupping your foot and it’s not under your foot. Because of that, it doesn’t really do anything more special.

So, your heel is pretty much only on about the same amount of Boost on the UltraBoost 20 and 19. Again, it’s still an incredibly comfortable shoe and it’s probably the most comfortable UltraBoost ever. However, it just doesn’t have as much Boost underneath your foot as it looks like it would.

Is that really that big of a deal? Not really.

Related: Hoka Shoe Size Chart



You’ll notice that the outsole has been completely redesigned.

The rubber panels on the outsole are made up of Continental rubber. Adidas has been partnering with Continental for years and that’s a good thing because the outsoles that they’ve created together last a very long time.

Related: Converse Sizing Chart

Adidas LEP Torsion System

But that’s not the biggest change. The largest change is the brand-new torsion system called Adidas LEP. What LEP stands for is Linear Energy Push.

Apparently, what this new torsion system does is reduce a lot of the torsional flexing while still giving you a lot of responsiveness.

Also, this new torsion system acts even more spring-like than the previous torsion system and literally gives a sort of spring to your step.

Midfoot Cage


Moving back in the sneaker, you get to the semi-translucent TPU midfoot cage which is really a throwback to the original UltraBoost.

Both the UltraBoost 20 and 19 had a midfoot cage which was really just one piece and extended up from the midsole. But this time around, it looks a lot more like the UltraBoost DNA’s midfoot cage.

You’ve got three individual stripes. Rather than extending the stripes down to the midsole, they’re actually sewn about maybe 5mm up from the midsole on to just the PrimeBlue upper.

I’m not totally sure why they decided to do that, but it feels fine on foot and I think it actually looks really nice.

Here’s a comparison of the UltraBoost Caged vs Uncaged.

Laces, Tongue, Ankle


Weaving to the midfoot cage, you’ve got these flat gray laces which, of course, match the upper.

What’s interesting is that when first get the shoe, the top lace eyelet is actually left untied to just allow you to customize the fit however you want.

Because this knit upper is a one-piece bootie construction, that means that there is no separate tongue. It’s really more of a sock going over the top of your sock than a regular sneaker’s upper.

Around the top of the ankle opening, you’ve got this exposed knit edge which doesn’t rub against your ankle.


Moving inside this shoe, you’ve got this really nicely padded neoprene portion which feels really great against your heel.

Then from the midfoot to the toe, there really isn’t any padding and your foot is just against the Primeknit.

Heel Counter


You’ve got a much thinner heel counter than you’ve had on the previous UltraBoosts. Unlike the UltraBoost 19 and 20, it doesn’t actually wrap over on to the Boost midsole.

A few things that I really like about the heel area of the UltraBoost 21 is that it extends up really nice and high so it can act as a pull tab (pic 8.24)

Even though it’s this high, these shoes don’t really irritate your Achilles tendon at all, which is great. It also has a lot of structure so you never feel like you’re not secure in the heel.



According to Adidas, 50% of the upper of the UltraBoost 21 is made up of textile and 75% of that textile is made up of PrimeBlue yarn.

Not only that, apparently there is no version or new polyester used anywhere on the upper of the shoe.

I’ve got to say it is so cool that Adidas is really focusing on using recycled materials especially in their mainline sneaker products like the Ultra Boost, the Stan Smiths, the Super Stars, and more.

For a while, they were just using it on special edition Parley sneakers, but now this sort of Parley Ocean plastic material is getting woven into their everyday sneakers, which is so cool.

That really seems to be the trend among a lot of other major sneaker brands. They all seem to be focusing on sustainability.

But I’m going to give Adidas some credit where it’s due because they really did seem to be the first company to go full tilt on using recycled materials before really anybody else, at least any of the major brands.

I know there are some smaller brands that are focusing on only using recycled materials and those brands are awesome, but as far as the big three, Adidas did really seem to be the first one to really focus on sustainability.

If this upper is made up of plastic bottles, how does it feel? Does it feel as good as regular knits?

Comfort & Breathability

Honestly, as far as breathability and comfort of this PrimeBlue upper goes, it feels great. The upper feels really nice and soft on your foot. It’s definitely a sock-like fit.

It’s a little bit thicker than regular Primeknit, but I don’t think that’s because of the materials that they’re using. I think that’s because they actually meant to make it thicker.

It’s also very breathable. But even though it’s cold outside, your feet still do get warm when you’re running. You really won’t have any overheating issues at all.

Which one is better?

So, with all of those performance improvements, is the UltraBoost 21 a better sneaker than 20?

Overall, I’d have to say yes. Even though the Boost in the midsole isn’t that much thick than you would think that it is, it’s still very comfortable and it’s still softer than the UltraBoost 20.

The PrimeBlue knit used on the upper definitely focuses more on sustainability while still containing your foot and still being very breathable and comfortable.

The LEP torsion system on the bottom reduces torsional flex while still giving you a little bit more responsiveness.

Yes, all of these performance changes are excellent and they definitely do help you with your run, but it’s not going to be like a ground-breaking difference between the two sneakers.

I think the biggest difference between the UltraBoost 21 and 20 is really the design. While that’s not a bad thing because design is very important especially when it comes to something that you’re actually wearing on your body, it’s really the biggest difference.


So, I guess my verdict is if you have a pair of UltraBoost 20 that you run in and you’re happy with it and they’re still in a great condition, stick with those.

However, if you’re looking to upgrade or you’re looking to get a new pair of UltraBoosts and you haven’t had a pair in a while, the UltraBoost 21 is definitely the shoe to go with.

Comparing the UltraBoost 21 to the 20, it doesn’t seem like it’s that great of a shoe, but that’s because the UltraBoost 20 sets such a high bar that the 21 is like just above that bar.

Even if you’re not a runner and you just love the aesthetic of this sneaker, you’re going to love the UltraBoost 21 for lifestyle wear because it’s incredibly comfortable.

Adidas Ultra Boost Size Chart FAQs

Generally speaking, the Adidas Ultra Boost runs true to size for narrow and regular feet. If you have wider feet, you might need to go up a half size or keep to the size you had in your UltraBoost 19 or 20.

The UltraBoost 5.0 DNA uses this recycled polyester, which means it’s not as going to be stretchy as regular Primeknit. So, for those wide-footed people out there, you probably should go up a half size in the UltraBoost 5.0 just to be able to get them on your feet a little bit more. They are a little bit more difficult to get on your feet because they, again, don’t stretch as much as the regular pairs.

If your UltraBoosts are snug, you can always remove the insoles, and then your foot is going to be riding directly on that Boost material, which isn’t a bad feeling at all.

Are Adidas sizes true to size?

First, you really need to get your feet measured to know what your true sneaker size is. The other thing is has a different preference on how they want their sneakers to fit and the kind of socks that you wear play an important role in that.

But generally, Adidas sizes are supposed to be true to size, but according to your foot shape and how you like to wear your Adidas shoes, you might need to size up or down.

As for sizing, the UltraBoost 19 fits pretty much true to size, at least for me. It definitely has a more snug fit around the midfoot and the toe of the sneaker, which, at the end of the day, I actually think I prefer.

Also, because the ankle area is so stretchy, it’s really easy to get your foot into the UltraBoost 19. So, I would suggest going with your standard UltraBoost size. However, if you have the chance to try on the UltraBoost 19 before you buy it, I definitely do that.

Are you supposed to wear socks with Ultra Boosts?

I guess you need to put on some socks if you’re wearing UltraBoosts, but you shouldn’t be wearing Nike socks with UltraBoosts. Or, if you only have Nike socks, make sure you wear some jeans.

The best socks to wear with UltraBoosts are no-show socks. Pick the color that matches your UltraBoost color and you’re good to go.

Are UltraBoost 21 true to size?

As far as sizing and fit, I would say the UltraBoost 21 does seem to run true to size for narrow and regular feet. If you have wider feet, it might not hurt to go up half a size. However, if you own any of the previous UltraBoost 19 or 20, the fit is very similar to those.

Is Adidas Ultra Boost waterproof?

Regula Adidas UltraBoosts are not waterproof, but if you want to enjoy walking in the rain more and not have to worry about water soaking your feet, get the UltraBoost Guard. These feature materials that are waterproof in order to give your feet comprehensive protection in humid environments.

What are UltraBoosts good for?

You can use your UltraBoosts both for lifestyle and running purposes. A lot of runners, including me, find the UltraBosst to provide the cushioning and comfort needed in the midsole, the structure needed in the upper and heel, and the traction and durability needed in the outsole. However, the UltraBoost 21 has a more athletic look than the UltraBoost 20 and 19.

Do UltraBoosts feel tight at first?

Your UltraBoosts should feel the way you want them to feel right out of the box, either snug or loose.

Is Ultra Boost the most comfortable?

The question I’m sure a lot of you have is “How comfortable are the UltraBoosts?”. The Boost midsole is incredibly plush and comfortable. The upper is very breathable and comfortable and feels very nice and soft on your foot. It also has that sock-like fit. The upper is going to contain your foot very well and you won’t have any slipping issues.

While the heel extends up really nice and high, it’s comfortable and it’s not going to irritate your Achilles at all.

What is Ultraboost Guard?

UltraBoost Guard is the waterproof version of the Adidas UltraBoost. The upper has some built-in properties that make the shoe waterproof in more wet conditions.

This pretty much wraps up this Adidas Ultra Boost size chart, review, and comparison. Have you grabbed a pair of the UltraBoost 21? If yes, what’s your experience in the 21 compared to the 20 or even the 19?   

About Eric Barber

Eric Barber is a happy father of two little angels, a husband, and a runner. He eats, sleeps, and dreams anything foot related: running shoes, walking shoes, sneakers, you name it. It all started when Eric was a shoe store specialist watching and fitting people's feet day in and day out.

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