Ski boots

Ski boots – and how they best work for you – is a deeply personal thing. There is no way to objectively review a ski boot. There are, however, some aspects about ski boots that we at least can describe and explain. That is what this page sets out to do.

In our opinion, everything there is to say about ski boots falls in these three themes: fit, flex, and features. The three ‘F’s, if you will. Their importance also follows that order: fit is more important than flex, and flex is more important than features.


Every boot fitter will tell you: fit is more important than anything else when it comes to ski boots. We agree. Obviously, every person’s feet are unique. However, we can give some general information on fit and sizing. And even that is not really something you can do blind. If you need new ski boots, try, try, and try them.

Ski boots have a specific sizing system: mondopoint. It’s ISO’s sizing standard for footwear. For adults, sizes in ski boots range from 22.5 to 30.5. That number refers to the actual length of your foot in centimeters. This corresponds with the length of the inside of the outer shell of a ski boot. The .5 on the end has to do with the liner thickness.

Last width
Mondopoint only says something about the length of the inside of the boot. The width of the widest part at the forefoot is measured in millimeters. Generally, 98 mm (at a reference size of 26.5 for men and mostly 25.5 for women’s boots) is considered ‘narrow’; 104 mm and up is considered ‘wide’. Note that the width scales up with size. So a boot that has a 100 mm width in size 26.5 may very well have a width of 106 mm in a 29.5 size. Here, too: try, try, try.

Some brands list the volume of their boots. In cc (cubic centimeters) or in terms of ‘high volume’ (HV), ‘medium volume’ (MV), or ‘low volume’(LV). This volume may say something about the instep height, ankle snugness, cuff fit, heel cup, toe box size, etc. However, there are no universal or set criteria for this.

When it comes to fit, all these aspects play together. Just try on a few boots to find the boot that is the best fit for your feet.

Measuring length, width, and instep (image by Blister Review)


In contrast to sizing and measurements, there is no standard for flex. The flex number ranges from 60 to 170 (60 to 140 for consumer ski boots). Generally one can say: the higher the flex number, the more direct that boot is in relation to other flex boots in the same product line by the same manufacturer.

You cannot compare a flex 120 boot to a 120 flex boot from a different manufacturer. You can’t even compare a 120 flex boot to a 120 flex boot in a different product line by the same manufacturer. The only fair comparison one can make, is between the 120 and 100 flex boot within the same product line by the same brand.

Not useless
This does not mean that flex is completely useless. It just is not very precise or standardized. But it is safe to say that 60-90 flex is for beginners that go slow and don’t generate too much force. 90-110 flex is for intermediate to advanced skiers of average size. 110+ flex is for advanced, heavy, and more demanding skiers.

Higher flex does not automatically mean a stiffer boot material (that would be measurable). The stiffness of the outer shell material does play a role, obviously. But also the stiffness and thickness of the liner is a factor. And the fit of the boot. Generally one can say: a snugger fit and less material make for a more direct boot and therefore a higher flex. There are many examples of boots of which the 120 and 130 flex versions only have different liners (the 130 flex boot has a thinner liner). And racers ski in boots two sizes smaller than their actual foot size, which makes for a more direct transfer of forces from the body of the skier to the skis.

There are many discussions on what flex boot a skier should have. These discussions are quite useless for two reasons: 1. Flex is not standardized, and 2. Fit trumps flex.

Forward lean explained


Of course, there are all kinds of features that may matter to a skier. Besides fit and flex, the number of buckles is a choice, the type of strap, walk/hike mode, etc. These are all features that seem obvious. There are some other features that are less obvious, so that’s what we’ll get into here.

Boot sole standard
Currently, there are three official boot sole standards. ISO 5355 is the ‘standard’ alpine ski boot standard. All alpine bindings are compatible with this standard. ISO 9523 is the Touring standard: tech inserts at the toe and at the heel, but with a slightly curved rubber sole for walking. These are compatible with touring bindings only. There are also some hybrid ski boots that are ISO 5355 and also have tech inserts (Fischer Ranger, Lange XT3, Tecnica Cochise, Nordica Strider, etc.) and are compatible both with alpine and tech bindings.

There is a new standard: ISO 23223: the GripWalk standard. These are compatible with all so-called ‘GripWalk bindings (5355 soles are also compatible). In short: make sure your boots and bindings are compatible.

Cuff alignment
Some ski boots have adjustable cuffs. This means that the upper part of the boot can be aligned with the lower leg fairly easily, by adjusting the screws at the ankle pivot point. Some brands call this ‘canting’, which actually is not the same (canting is aligning the entire boot by grinding the sole of the boots).

Forward lean
The forward lean of a ski boot adds to its directness. Some boots have a spoiler, a little removable wedge that goes between the outer shell and the liner at the top backside of the cuff. Removing the spoiler will decrease the forward lean by 2 degrees or so. Racing boots have a forward lean of around 18 degrees, cruising and freeride boots typically are a bit more upright with 12-14 degrees.

A 2015 Tecnica Cochise Pro with walk mode and different styles after-market soles. Image by Blister Review

Boot fitting

Getting your boots ‘fitted’ means first and foremost getting the boots that fit your feet and you as a skier best right out of the box. In most cases, though, some work still has to be done to ensure the best possible fit and a good skiing experience both in terms of comfort and performance.

Fitting the boot
Most feet have small bumps and points where a ski boot out of the box doesn’t fit perfectly yet. A good boot fitter can stretch, grind and shape the outer shell and liner to make the boot fit perfectly. This is important. You don’t want small pressure points; that really ruins your day. And a single slightly pinched blood vessel can restrict blood circulation and result in a tingling sensation or cold feet. 

Foot support
The insole of most ski boots is pathetic. It is merely a little rug with the brand name on it. It does not give any support to your feet. For this, most people really benefit from after-market insoles. There are ‘standard’ ones that do the trick for most people: ensuring a well-supported foot that is stable and aligned inside the boot. For some people, more specialized custom insoles can be a solution. Make sure you visit an expert for that.


Important: boots can only be made bigger, not smaller. In terms of sizing, when in doubt (or with two very differently sized feet) get the smaller, narrower boots. Making them bigger where needed is not a problem for a good boot fitter.

Ski boots are a very important part of the total ski gear package. Maybe even the most important part. Make sure they fit well. That’s the most important thing. Visit a proper boot fitter to get you a pair of well-fitting, well-fitted boots. That should be your first ski gear purchase.