Kids' Ski Boot Size Chart & Mondo Guide

Ski boot sizing can sound complicated, with Mondo, European sizes and shell sizes all entering the conversation before your child has even put a boot on. Start with foot length, then check how the boot fits. Fortunately, the important part is remarkably simple: Mondopoint is based on the length of the foot in centimetres. A foot that measures 19.5 cm gives you a starting ski boot size of Mondo 19.5. Regular shoe-size conversions can point you in the right direction, but measuring the actual foot is more reliable.

"All ski boots (kids and adults) are now using 'Mondo sizing'. This is a universal sizing based on centimeters. The plastic outer shells are usually only in whole sizes, while the inner liners are in half sizes." - Ski Tips for Kids

What is Mondo size?

Mondopoint—or Mondo, because apparently skiing didn't have enough terminology—is the sizing system used for ski boots. Measure the foot in centimetres and you have your starting Mondo size. A 20.5 cm foot points you toward a 20.5 Mondo boot. That's considerably more useful than knowing your child wears a size 1 sneaker, particularly since everyday shoe sizing varies between brands. When someone asks what ski boot size your child needs, start with their foot length rather than the number on their running shoes.

How to measure your child's foot for ski boots

Have your child put on the thin ski socks they'll actually wear skiing and stand with their heel against a wall on a hard floor. Mark the end of the longest toe and measure from the wall to that mark in centimetres. Measure both feet. Bodies have an irritating habit of not being perfectly symmetrical, so use the longer measurement as your starting point. Measuring while standing is preferable because the foot is bearing weight. REI similarly recommends measuring both feet while standing and using the longer measurement. If the longer foot measures 19.5 cm: Start around Mondo 19.5.

How should kids' ski boots fit?

A ski boot should fit snugly and securely without being painful. This matters because ski boots aren't just winter footwear. They're the connection between your child and their skis. When your child moves a foot or leg, the boot needs to transmit that movement to the ski. Put a little foot in a much-too-big boot and some of that movement happens inside the boot instead. New ski boots can also feel tighter initially because liners compress somewhat with use. That's another reason not to judge a boot exactly like a running shoe. For a child, we're looking for the sensible middle ground: secure enough to ski properly, comfortable enough that their feet aren't the subject of every chairlift conversation.

Don't buy them huge

It's tempting to buy ski boots substantially too large so they'll last another season—or possibly until university. But excessive room can let the foot move around inside the boot and make it harder for the skier to control the ski. Some growing room is understandable. “They'll grow into them” shouldn't be the entire fitting strategy. If you're unsure, this is where a good ski shop or boot fitter earns their keep. A professional can assess not just foot length but the shape and volume of the foot and how the child's foot sits inside the shell.

What about shell sizes and half sizes?

The number printed on a ski boot doesn't necessarily mean every half-size has an entirely different plastic shell. Manufacturers may use the same shell for more than one Mondo size and make sizing differences through the liner or other components. The exact size breaks can vary by manufacturer. For example, SCARPA's published sizing information notes shared shells at particular half-size breaks. This is one more reason Mondo is a starting point, not a substitute for actually trying on the boot. For parents, the takeaway is simple: don't get too hung up on whether the conversion chart says 19, 19.5 or a particular street-shoe equivalent. Measure the foot to choose a starting size, then try the boot on and check the fit.

One pair of ski socks. Really.

If a child's feet are cold, the natural parental response is often: More socks. Ski boots are designed to fit fairly closely. Stuffing extra socks into them can make the boot tighter without necessarily making the foot warmer. A single pair of well-fitting ski socks is the better starting point. This is also why you should measure and try on boots wearing the kind of socks your child will actually ski in.

Common kids' ski boot sizing mistakes

Most boot-sizing trouble comes from a handful of very reasonable ideas that don't work quite as well as you'd expect:

• Using sneaker size as the measurement. It's a useful clue, not a foot measurement.
• Buying way too much growing room. Great for growing. Less great for skiing.
• Adding multiple pairs of socks. More isn't always warmer.
• Assuming every brand fits the same. Feet and ski boots both come in different shapes.
• Assuming discomfort automatically means “too small.” Pressure can come from the shape, width or volume of the boot as well as its length.

And, of course, there's the classic: “They said they were comfortable in the store.” They are children. New information will become available approximately seven minutes after you arrive at the hill.

When should you see a ski boot fitter?

For rental boots, a knowledgeable rental shop should be able to get your child into an appropriate size and change the boot if something clearly isn't working. If you're buying boots, professional fitting becomes more worthwhile—particularly if your child skis frequently, has persistent pressure or pain, has unusually narrow or wide feet, or you're simply not confident about the fit. Even with a perfectly measured Mondo size, foot shape still matters. REI and evo both recommend professional fitting when possible because length is only part of getting a ski boot to fit correctly.

Just give me the numbers

If you came looking for a kids' ski boot size chart, here's the quick-reference version. The most important column is the first one. Mondo is based on foot length in centimetres. The US, UK and European sizes are approximate conversions and can vary somewhat by manufacturer, so use them to get into the neighbourhood—not to buy a boot blind. Published conversion charts themselves vary slightly, which is another reason measuring the foot is preferable.

One oddity worth noticing: there isn't a neat, universally used Mondo size at every half-centimetre in the smallest children's sizes. That's why the chart jumps from 17.5 to 18.5 and then 19.5 in this commonly published conversion sequence. Individual boot manufacturers may offer or label their sizes differently. 

More Ski Tips for Kids

Sock Talk · Boots with Buckles · Kids' Ski Gear Guide (coming soon) · How to Dress Kids for Skiing (coming soon)