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How to Choose an Alpine Ski Boot

Selecting a new pair of ski boots can be a little overwhelming, to say the least. Every year, ski companies roll out their shiny new boots, often with various flex, size, and width numbers slathered across the shells. If you’re wondering what it all means and how these numbers correspond to your specific skiing needs, we’ve assembled a little guide designed to help you make sense of these seemingly cryptic markings.


Size is one of the first issues that should be addressed when you’re considering new boots. Ski boots use an international foot measuring system called Mondopoint, which is the length of your foot measured in centimeters. You’ll often see boots marked with this number on the toe and heel lugs, expressed in whole and half sizes. While many manufacturers often include a size conversion chart for their boot shells, you can simply determine your Mondopoint size by tracing your foot on a piece of paper. Then, measure from your heel to the end of your longest toe, in inches, and multiply by 2.54. Round this number to the nearest half centimeter, and this is your Mondopoint size. For example, a foot measuring 10.5in is 26.67cm, or 26.5 Mondopoint. Ski boot shells are made in full sizes only, with varying insole thicknesses making up the difference. This means that a 26.0 and 26.5 shell will be the same length (often around 310mm, which should be printed on the side of the heel) with the 26.5 featuring a slimmer insole than the 26.0.

Since you’re determining the length of your foot, it’s a good idea to assess your foot’s width as well. Manufacturers measure the interior of a boot’s shell in millimeters at the widest part of the forefoot. This number will be expressed as “last width.” And while you don’t need to have an exact forefoot width measurement, it’s good to know that a 100mm last width is fairly standard (race boots usually feature last widths ranging from 95-97mm, while 104mm is considered “wide”). If you usually wear wide, “EE” tennis shoes, for example, it’s a safe bet that a 104mm last will be an appropriate match. If you wear a standard “D” width shoe, then a 100mm last will most likely fit your foot the best.


Once you have length and width numbers sorted, the next step involves an honest self-assessment of your skiing ability. This will help determine the how stiff your boots should be. To simplify things, we’ll go with the standard classification procedure: level one represents a beginner skier, two is an intermediate, and three is advanced. Of course this can be fine-tuned, but it provides you with a starting point to help determine how stiff your boots should be.

When you’re wearing a ski boot, as you move your knee forward, you’re essentially flexing the boot’s shell. How easily the upper shell hinges forward is measured using a numeric flex index scale. This scale usually ranges from around 50 to 130, with the most flexible boots measuring around 50 and the stiffest race boots measuring around 130+. It’s important to note that there is no standardized flex index across manufacturers, meaning that Rossignol‘s 100 flex will not be the same as Tecnica‘s 100 flex. The reason for this is that shell materials, buckle positioning, and varying hinge locations all factor into a boot’s flex, making a universal flex index nearly impossible to calculate. But it’s good to know that once you determine your flex range, you’ll be able factor it into your boot selection accordingly. The proper flex will not only let you maneuver the ski as it was intended, but it will also be more comfortable than being stuck in a boot that’s too stiff for your ability level.

Starting with an adult male skier, a type one (beginner) should look for a boot with a flex in the range of 50 to 85. A type two (intermediate) will be most efficient in a boot with an 85 to 110 flex index, and a type three (advanced) skier will get the most out of a boot with a 110 to 130 flex index. For a woman, simply reduce these numbers by 20 (e.g. an intermediate woman skier will benefit most from a boot carrying a 65-90 flex index). It’s also good to remember that height and weight factor into boot flex—a taller woman will be able to flex a boot more efficiently than a shorter woman, regardless of ability.

Final Sizing Suggestions

Fit is best determined by a skilled bootfitter, but if you can’t try the boot on before purchasing, know that your Mondopoint measurement often directly correlates to your appropriate shell size. For example, a male skier whose Mondopoint measures a 26.5 will most likely wear about a 26.5 ski boot, which is probably a full size smaller than his street shoe size. A good rule of thumb is to downsize from your street shoe by a single size. Please note that if you order two boot sizes to see which fits best, make sure they’re a full size apart. As previously mentioned, a 26.0 and 26.5 will share the same shell size. A 26.5 and 27.5 would be a better option when ordering online.


Video Transcription

As the connection point between you and your skis, ski boots are arguably the most important aspect of your ski setup in regards to both comfort and performance on the hill. Unlike street shoes, ski boots are measured on a universal scale called Mondopoint, which is simply the length of your foot measured in centimeters. To find you approximate Mondopoint size, all you need to do is trace the outline of your foot on a piece of paper and measure from the back of your heel to the tip of your longest toe with a measuring tape. Ski boots are assigned a flex index rating that typically ranges from 50 to 130. Although some expert level race boots are rated as high as 150. This number is an indication of how soft or how stiff the forward flex of the ski boot can be. Generally beginner to intermediate skiers will prefer a flex rating between 50 and 85, while advanced skiers will be best suited with a boot between 85 and 110.

Expert level skiers will look for boots will look for a flex index of 110-130 range. Last width is a measurement taken from the boot’s interior at the widest part of the forefoot. This measurement typically ranges from 95-106mm, and while the variation in width may seem marginal, a few millimeters can have a huge impact on how your boots feel and perform.

Typically, wider lasts are associated with a more comfortable fit while narrower lasts are sought after for greater performance and ski responsiveness. A 100mm last width is considered the happy medium. Although, every foot shape is different and if you have a particularly wide or narrow foot you want to take that into account when selecting a last width.

If you have any questions about choosing the perfect ski boot for you, be sure to call or chat in with our knowledgeable Gearheads at


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