How to Buy Ski Boots: Finding the Right Size & Fit

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Knowing how to buy ski boots can feel like an overwhelming task. It is the most difficult, and also most important, decision you’ll make when putting together your ski setup. Ski boots give you direct connection with your skis and thus have a major effect on how energy is transferred to them. This connection is what gives you maneuverability and power on the slopes.

Additionally, feet are the most common pain and discomfort points while skiing. Expect to have a poor ski experience if you’re not skiing in a boot that’s right for you. So, choosing the right ski boots is imperative if you want to improve your skiing ability and be comfortable on the mountain. This guide provides all the information you need to make a great choice!

In This Post

Components of a Ski Boot

Let’s start with a quick rundown of a ski boot’s construction. Understanding the terminology is the first step to figuring out how to buy ski boots that are right for you. 

Ski Boot Model


1 of 7

Power Strap

2 of 7

Upper Cuff

3 of 7


4 of 7


5 of 7

Footbed / Insole

(located inside the boot)

6 of 7

Boot Sole

7 of 7
  • Non-moldable: These liners offer generic padding and stability. With use, the continuous pressure of your body weight will cause the liner to conform to your foot’s shape. This is particularly true around pressure points, such as the forefoot.
  • Thermoformable: Foam liners that utilize the heat from your foot to achieve a custom fit.
  • Custom Moldable: Some liners can use artificial heat sources to achieve a truly custom fit. Creating a custom mold is best done with the assistance of a local shop or boot-fitter, although some are possible to do yourself at home.

Ski Boot Flex

Ski boots are given a numerical designation between 60 and 150 called “flex” to indicate how stiff the boots are. Higher flex numbers indicate a more rigid boot. Choosing the flex of your ski boot comes down to your ability and body type. The more advanced or heavier you are, the more stiff the boot needs to be to allow for better power transmission from the legs to the skis.

Ski Ability Women's Flex Index Men's Flex Index
Beginner ~ 50 - 70 ~ 60 - 80
Intermediate ~ 70 - 90 ~ 80 - 100
Advanced ~ 90+ ~ 100+

Ski Boot Size & Fit

How to buy ski boots that are comfortable and perform well largely depends on finding the right size and fit. Ski boots should fit tightly without cutting off circulation or causing painful pressure points. Below we cover how to determine your ski boot size and how the width, length and volume impact the overall fit. If you need a refresher on how to put on ski boots and skis, check out this other post of ours.

How should ski boots fit?

Ski boots should be snug without causing any discomfort. Unlike with normal tennis shoes, extra room at the end of your toes is not recommended. Your longest toes should feel slight pressure against the end of the boot when you are in an upright standing position with your boots buckled. Once you start skiing, you should be leaning slightly forward, which causes your foot to slide back in the boot, providing just enough space for a perfect fit.

Should you buy ski boots a size bigger?

Buying a size up for extra room or to “grow into” is a bad idea. Ski boots only perform when fitted correctly, and an oversized boot can make skiing difficult. Even if you end up purchasing boots that are slightly too small, they can be adjusted by a bootfitter to provide more room. A boot that is too large, on the other hand, can not be shrunk.

Skiers forming a circle with their ski boots

Ski Boot Width (Last)

The shell width at the widest part of the forefoot is called the “last” of a ski boot. This is a general indication of how narrow or wide the boot is. You can get an estimation of your own last by tracing an outline around your foot and then measuring the widest part in millimeters.

  • Narrow: 96 – 98 mm
  • Average: 100 mm
  • Wide: 101 – 103 mm
  • Very Wide: 104 – 106 mm

Tighter fitted boots provide more precision but are less comfortable. For that reason, racers often size to the tightest width they can to maximize performance. The casual resort skier may want a little extra room, but don’t overdo it. Your ski boot should fit snugly for adequate control over your skis, but not so snug that it feels uncomfortable.

Ski Boot Length

You may be wondering if ski boot sizes are the same as shoe sizes. The quick answer is no. An international standard of sizing is used, called “Mondopoint”, which essentially corresponds to the longest part of your foot (in centimeters). Ski boots should fit your actual foot length much more closely than normal tennis shoes do.

How to Determine Ski Boot Size

Your ski boot size, or mondo size, is easy to figure out. It is the length from your heel to your longest toe in centimeters. To measure, put a piece of paper on the floor against the wall. Put the back of your heel against the wall with your foot flat on the ground on top of the paper. Measure the distance from the wall to the end of your longest toe. When between sizes, round down half a size to account for compression of the boot liner.

If that sounds like too much work, you can also check out Powder7’s ski boot size calculator to get a rough idea.

Mondo 21.5 22 22.5 23 23.5 24 24.5 25
Women's U.S. 5 5.5 6 6.5 7 7.5 8 8.5
Men's U.S. N/A N/A N/A 5 5.5 6 6.5 7
Mondo 25.5 26 26.5 27 27.5 28 28.5 29 29.5 30 30.5
Women's U.S. 9 9.5 10 10.5 11 11.5 12 N/A N/A N/A N/A
Men's U.S. 7.5 8 8.5 9 9.5 10 10.5 11 11.5 12 13

Ski Boot Volume

Even though the length and width are indicative of a foot’s overall volume, the primary indicator is the height of the instep. Your instep is the top of your foot, above the arch, where your foot meets your ankle. To determine the height of your instep, measure from one side of your heel over and around your ankle to the other side of your heel. If that distance is about the same length in centimeters as your mondo size, you have an average height instep.

So, why does this matter? Too much space above the instep can cause your foot to slide around, making it hard to maneuver your skis. Not enough space above the instep can make your foot feel constrained and cause pain.

Ski boots come in different volumes that typically correlate with the width, or last. Skiers with wide feet tend to need high-volume boots, while skiers with narrow feet tend to need low-volume boots. However, if you have a narrow foot but a high instep, a high-volume boot is likely better even if it doesn’t quite match the width of your foot. This is because it’s difficult for bootfitters to expand the volume above an instep.

Keeping Your Feet Warm

An important, but often overlooked, factor in how to buy ski boots is your socks. The ski socks you choose will impact how your ski boots fit and how warm your feet are when you’re on the mountain. Because ski boots are supposed to be form fitting, your ski socks should be thin and form fitting as well. Additionally, it is best to opt for ski socks with moisture wicking properties to keep your foot as dry as possible. Wet socks and feet can cause blisters and cold toes.

Darn Tough Outer Limits OTC Padded Light Cushion Sock - Men's

Is it bad to wear two pairs of socks skiing?

Do NOT make the mistake of wearing two pairs of socks while skiing. Similarly, thick socks are also not recommended for skiing. This can be counterintuitive for skiers that want to bundle up and stay warm. Thick socks can cram your feet and impede your circulation, which will make your feet colder. Wearing two pairs of socks only compounds this issue. Not only will you have less room in your ski boot with two pairs of socks, but your foot may also slide around between your sock layers and make skiing more difficult.

Ski boot heaters can be a lifesaver if you tend to run cold  or will be skiing in frigid conditions. The heater is a pair of heating elements that can be connected to the top of your insoles. These elements are then wired to a battery pack that attaches to the outside of your ski boot. The batteries are rechargeable, and the heat can usually be adjusted depending on the temperature outside. In addition to heaters, ski boot dryers are also very helpful! Using a dryer after a long day on the slopes ensures your boots are sweat-free and snow-free before you put them back on the next day.

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Other Ski Boot Features

  • Buckle Micro Adjustments
    Some boot buckles can be shortened or lengthened by twisting them. Making small adjustments to the length of your buckles fine tunes their tension to further improve your boot’s fit.
  • Interchangeable Soles
    Certain boots have the ability to swap the hard soles on the bottom of the boot. This is commonly used by backcountry skiers to switch from an alpine sole to an alpine touring sole. It’s important to check that any interchangeable soles you purchase are still compatible with your ski bindings.
  • Flex Adjustment
    Some boots have a mechanism to make slight flex adjustments. This is usually a metal dial on the back of the boot that needs to be turned with an Allen wrench. Although only small adjustments can be made, they can be enough to achieve the right stiffness to balance comfort and performance.
  • Walk/Ski Mode
    Boots with a walk/ski switch on the back of the boot can unlock the upper cuff from the shell to give you slightly more mobility when walking. This is a nice feature to use when you’re waiting in a long gondola line or taking a break at the lodge. Just remember to flip the switch back to ski mode when you get back on the mountain. Otherwise, the top of your boot will feel loose.

Custom Ski Boot Fitting

Bootfitters can make small tweaks and customizations to your boot’s size and fit that drastically alter the overall comfort of your boot. For example, they can adjust the size of boot shells to eliminate pressure points. A good bootfitter can be a game changer for any serious skier, and most people feel the benefits are more than worth the price.

How much does custom ski boot fitting cost?

Custom ski boot fitting generally costs somewhere between $900 to $1,200. This depends on the level of service being offered and whether you want a new boot, liner, or insoles. Some bootfitters allow you to bring in the boots and liners you’re currently using to just make adjustments.

How long does custom ski boot fitting take?

A custom boot fitting can take anywhere from 1 to 3 hours to be done right. You may also opt to have additional adjustments made after the initial fitting. Even with custom boots, you may notice small irritations once you start skiing in them and want to get the fitting refined.

Salomon ski boot

What is canting?

Canting is a process where the sole of the ski boot is grinded to a specific angle to accommodate skiers with inward or outward pointing knees. A bootfitter will measure where the center of your knee mass is traveling to determine what angles and adjustments need to be made.

Are custom footbeds / insoles worth it?

The footbed is maybe the most crucial piece of a ski boot as it provides balance, support, and comfort to your feet while you ski. Bootfitters can take a mold of your foot to create a footbed perfectly crafted to fit your exact foot size and shape. Sounds amazing right?

Swapping out the stock insoles for custom ones can make a world of difference for your ski boot fitting. Fully custom footbeds can be up to $100, but are well worth the price when the difference can completely change your ski experience. Even buying standard insoles from a ski shop is an upgrade over most of the stock insoles, which are barely more than thin, flat pieces of foam.

Final Thoughts

Your ski boots are the foundation of both your skiing ability and comfort on the mountain. Therefore, it is worth the time to research and learn about them, as this will help you in determining how to buy ski boots that you will love. If you don’t feel confident in buying a good boot, consult a professional bootfitter or an associate at your local ski shop. 

Remember, finding the right fit is everything when it comes to ski boots. Although it may be tempting to choose ski boots based on their colors or other aesthetics, comfort is more important. Looking stylish won’t matter if you are too miserable to ski in your boots and show them off. We hope this guide has provided you useful tips in how to buy ski boots that are right for you. Good luck and see you on the slopes!