Ski Boot Size Guide: How to Buy Properly-Fitting Ski Boots

Published on 09/20/2023 · 9 min readSki boots can make or break your experience up on the mountain. But finding the right pair can be tricky. Ski expert Aidan Anderson breaks down what you need to know.
Aidan Anderson, Ski Expert
By Ski Expert Aidan Anderson

Photo by Michal Durinik

Finding the right ski boot can be both the most difficult and most important part of building your ski setup. It can also feel downright impossible, but it’s not, I promise. There’s a lot that’s good to know, and also a fair amount that you really don’t need to worry about.

First, let’s get this out of the way right off the bat: ski boots SHOULD NOT destroy your feet after a day on the hill. The idea that ski boots have to be uncomfortable in order to perform well is a thing of the past, born out of the hardcore ski racing roots that most boot companies were forged in. With advances in technology and changes in style, pain is no longer the indicator of performance. With that being said, let’s talk about a couple of the things that go into boot fitting.

What’s my size?

Photo by Bear Fotos

You’ve probably seen the strange if not downright confusing sizes associated with ski boots, and wondered why you can’t use your shoe size to buy boots. There’s a couple of reasons for this. Everyone knows that US shoe sizes can vary between brands. Say you wear a size 9 in your favorite sandals, but your running shoes are somehow a 10.5. Not the end of the world when buying shoes, but it would be a nightmare for ski boots.

This is why boots are measured in what’s called Mondopoint, or mondo sizes. Sounds confusing, but it’s essentially a direct measurement in centimeters of the length of your foot. This is where the funky sizing numbers come into play. For the most part, adult ski boot sizes run from 22.5 to 32.5, with some obvious outliers for larger or smaller feet. Now, the major advantage to knowing this size is that once you know, you know. Every company uses the same standardized sizing, which means you’ll always know what your size is when trying on a new boot. Now, the obvious question is, how do I find my mondo size?

The easiest way to find your mondo size is to have your foot measured at a ski shop. Shops will have measuring devices pre-marked in Mondopoint, which makes things quick and easy. That being said, not all of us have access to ski shops, so how can you find it at home? You’ll need a couple of things.

  1. A wall
  2. A ruler or tape measure
  3. A piece of paper
  4. A pen

All you need to do is lay a piece of paper on the ground up against a wall, and stand on it. You’ll want your heel firmly up against the wall, the widest part of the inside of your foot lined up with the edge of the paper, and your weight fully planted on that foot. Then, simply take a pen and make a mark at the tip of your longest toe (which may not be your big toe—it’s more common than you’d think). Once you have your mark, just measure that length in centimeters, and there you have your right size in mondo! Keep in mind, nearly every ski boot company will measure their boots on the half size, (26.5, 27.5, etc.) so round up to the nearest half size. Keep this paper for the next step in the process.

What is the “last” of my boot?

There are a couple of other numbers that you might have seen when looking at ski boots, one of them being the “last.” While it might seem confusing having so many different numbers associated with every boot, trust me, they serve an important purpose. Last starts to get more into foot shape, rather than just foot size.

Every ski boot will have a last measurement in millimeters, usually ranging from about 96mm to 105mm. All this means is the width of the boot around your foot. Simply put, smaller last widths are for narrow feet, and larger last widths are for wide feet. It’s easy to measure your last at home using the same technique we used for length. If you saved the paper you used to measure your mondopoint size, you can use that to measure your last. Simply stand in the same place with the inside edge of the ball of your foot in line with the edge of the paper, and then make a mark on the widest part of the outside of your foot, below your pinky toe. Some quick math from centimeters to millimeters, and there you have it!

Now, you may be wondering why this matters. A correct width in your boot is essential to the right fit and the comfortable fit for several reasons. In almost every case of foot pain caused by ski boots, the reason is that some part of your foot is moving inside the boot. If your boot is too wide, your foot can roll side to side every time you make a turn, putting a ton of stress on the muscles in your foot. The same is true for a boot that’s too narrow. If your foot is wider than the bottom of the boot, that means it will curl up on either side when you go to make a turn. Not fun.

What is the “flex” of my boot?

Now on to the last major number you’ll see when looking at boots. The flex of a boot is usually found in the name itself. For example, say you are looking at the Rossignol Alltrack 120. Rossignol is the manufacturer, the model is the Alltrack, and the flex is 120. They do this because chances are, they also make an Alltrack 130, as well as an Alltrack 110. It’s confusing, don’t get me wrong, but it’s less complicated than it seems. The lower the number, the “softer” the boot; the higher the number the “stiffer” the boot.

Graphic from the article Ski Boot Flex Explained

Now, a lot of the flex has to do with the weight and height of the skier, but it also has to do with the ability level. Most men’s boots will range from a 90 flex to a 130 flex, and most women’s boots will range from a 60 flex, to a 120 flex. This is unfortunately the least standardized figure from ski boot manufacturers, meaning that a 100 flex in a pair of boots from Rossignol and a 100 flex from Head will not always feel identical. That being said, it’s a great way to ballpark things.

The advantage of a softer boot is for beginner skiers. The boot is more forgiving at slow speeds, and requires less energy to flex when making turns and navigating terrain. Additionally, for smaller skiers, a softer boot will be easier to maneuver because you will need less leverage to flex the boot.

The advantage of a stiffer boot is for advanced skiers. A stiff boot will provide more rebound when flexed, meaning that higher impact turns, landings, and maneuvers will take less energy out of your legs. You will also feel more support in technical terrain.

How should my boots feel?

Photo by Michal Durinik

All this technical knowledge is great, but it all comes down to how your boot feels on your foot. We’re looking for a snug fit, but a comfortable fit. A couple of things before we jump in: always try your boots on with full length socks, preferably ski socks specifically, and always buckle them all the way up before gauging the fit. If you’re looking for a real quick size estimate, you can also “shell fit” your boots. Just pop out the liners, and push your foot all the way to the front of the plastic shell. Ideally you should have about a finger’s width or just slightly more behind your heel.

When you go to put on your boots, the first thing to check is the buckles. They are one of the best and easiest ways to indicate how well your boot fits the shape and size of your foot. Most boots will have either three or four buckles on each. A toe buckle, an instep buckle, and either one or two cuff buckles. Additionally, many boots will also have a “power strap” which is a velcro strap that cinches around the top cuff of the boot. It’s best to start from the bottom and work your way up. Take care to ensure the tongue of the boot is situated all the way inside the boot, and that all plastic pieces overlap each other correctly. Then, buckle each buckle only as tight as it needs to be to stay closed. Once all buckles are closed, you can go back through and tighten each as much as it takes to feel snug but comfortable.

Now, take a look at your instep buckle. This is the best indication of how well your foot fills the volume of the boot, and is the most important buckle by far. This is what’s keeping the heel of your foot firmly planted in the back of the boot, and what will ensure your foot isn’t moving around inside while you’re skiing. Ideally, with a perfect fit, that buckle should always be resting around the middle of the possible settings. If you have to max out the buckle to feel snug, the boot has too much room, and if you can barely get it closed on the first notch, you don’t have enough room. As for the other buckles, the toe buckle has little to no impact on the fit, and the cuff buckles are much more user-preference in terms of how tight they should be.

Do I need a custom fitting?

Photo by Bear Fotos

Something to keep in mind with ski boots is that everyone’s feet are incredibly different, and everyone has different needs. While manufacturers do an incredible job making a wide range of boots to fit different people, there will always be those who need something a little different. If you have a pair of boots you love, but are having trouble with a certain specific aspect of them, take advantage of how much customization is available for ski boot fitting. Most ski shops have an incredibly talented team of boot fitters with the experience and knowledge to fine tune your boots based on your needs. Also, and I cannot stress this enough, GET INSOLES. Every ski boot out there can benefit from a pair of insoles with good arch support, and for those with specific needs in that department, custom insoles are a great option for eliminating nasty foot pain while skiing.

Hopefully that gets you started! There’s always more to learn about boot fitting, but if you have any questions, reach out to me or one of my fellow Ski experts here on Curated!

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