Ski Boot Buying Guide

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Skiing doesn’t have to hurt your feet. In fact it shouldn’t. A proper fitting ski boot can make all the difference on a big pow day or railing a gate during a race. The difficult thing is that everyone has different shaped feet. From narrow and wide, to bone spurs or cankles, no two feet are alike. Manufacturers try to develop ski boot technology around a range of different types of feet but ultimately, one brand of boots will feel better than another. So to shed some light on the differences, here is our ski boot buying guide.

Shell Fit

To start, ski boot shells are always measured in half-sizes. So a 26.0 and 26.5 shell is the same thing. This sizing is based off the Mondo system, or more or less, your shoe size in centimeters. This system was adopted to provide a standard fit for all sorts of footwear. So a boot made in France will have the same Mondo size as a boot made in the U.S.A. Not every brand complies with this sizing, so it is key to always try boots on before you buy them. Another size difference is in the type of liner and amount of padding used. Due to these differences in sizing, we can narrow shell fits into two categories: Performance and Race fits.

To achieve the ideal shell fit, remove the liner of a boot you’re considering and insert your foot in with your big toe all the way forward and contacting the front of the shell. Here you can use your finger as a measurement, or a highlighter, or any measuring tool that is close to 15 mm in diameter.

Performance Fit: If you can fit your finger in behind your heel and between the back of the shell snugly, you have a performance fit that will be most comfortable. If you have some wiggle room or you can fit more than one finger or measuring tool, the shell is most likely too big.

Race Fit: Less than 15 mm of space is considered a race fit and will be very snug. Racers like this for maximum energy transfer to their skis. However, depending on the brand and what you are trying to accomplish as a skier, a boot with a race fit can be highly uncomfortable or painful.

Ski Boot Lasts

A ski boot last is the width in millimeters across the forefoot and is based on average measurements of a slight diagonal across the metarsals. Basically, the widest point of your foot dictates the last.

Narrow Last: People with narrow feet will want a narrow lasted boot. Usually, the last of the boot will measure somewhere between 97–98 mm. Race boots can go as low as 95 mm to achieve a tighter, more direct fit. This will most likely be a very uncomfortable fit for someone with a medium or wide foot.

Medium Last: Medium or average boot lasts will fit most skiers and have a width of about 100-102 mm. Performance alpine boots usually fit into this category as they are considered some the most comfortable widths. Ski touring boots usually use a last within these widths or wide to keep feet comfortable while walking or skinning.

Wide Last: People with wide feet will find comfort in a boot with a last between 102-106 mm. If you wear wide shoes or if you are willing to trade performance for comfort, I would look for a big volume boot with a wide last.

Ski boot lasts also go hand in hand with volume. Big wide feet usually take up a lot of space. So ski boot manufacturers try to design boots accordingly. Of course, there are some inconsistencies. For example, people with wide, flat feel and narrow ankles will be looking for a very specific boot.


Ski boot flex or stiffness is determined by skier type and the ski discipline the boot is going to be used for. Race boots are meant for very powerful skiers that need leverage over big, stiff skis. A beginner or intermediate skier is going to need more compliance out of their boots to initiate turns, meaning they will need a softer flex boot.

Flex is based on a measurement scale, or flex index, between 45 and 130. Some race boots will be rated even stiffer. A smaller number is softer and a higher number is stiffer. Not all manufacturers flex indexes match up. For example, one manufacturer’s boot might claim to flex at 130 but really flex lighter at around 120. Below is a simple flex chart to go by based on skier ability.

65-80 flex – beginner skiers, very soft
85-100 flex – intermediate skiers, firm flex but still forgiving
105-125 flex – Expert level skiers, very firm
130+ flex – Race level, very stiff plastic shell

However, this is just a chart to use as a starting point. To really know how a ski boot flexes, you’ll want to try it on.


Every pair of ski boots comes with a liner. Often, manufacturers design the shell and liner to work in unison. Aftermarket liners like ZipFit or Intuition can be purchased for extra performance or for enhancing the fit with problem feet. However, most liners will work just fine with the shell they came with. And almost every liner and shell are meant to be heat-molded together for the ideal fit. A really innovative company, Fischer, have develop vacuum fit ski boots that perfectly match your feet, ankle, and lower leg. Their proprietary fit process gives you the ideal fit for a range of different ski disciplines. If you haven’t seen them yet, you should definitely check out the Fischer Vacuum ski boots.

In The End

Buying a ski boot comes down to how you ski and the anatomy of your feet. Some people have feet that require special attention. Start with research on the internet. There are great review sites out there like that provide an informative starting point.

Then take that information to an experienced ski shop and make your decision. Getting your boots fitted by a professional boot fitter will give you a more satisfactory and fun experience out on the hill. Plus, a qualified boot fitter is not scared of your smelly feet and will be happy to make the best suggestions possible. Some you may not even considered, based on your research.

Buying ski boots online can be dangerous; ski boots change a lot year-over-year and what you think you know fits might not next season. Check out our custom ski boot fitting to learn more about what our Experts can do for your feet this ski season.

Paul Boyle, Marketing Specialist