How to Size Alpine Touring Boots: A Bootfitter’s Guide

Ski Touring 101 / Gear guide

CRIPPLE CREEK BIKE AND BACKCOUNTRY

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Sponsored by Dynafit. Equipment recommendations reflect our shop’s guidance.

By the Cripple Creek Bike and Backcountry ski touring team  •  Updated November 2026

Touring Boots Should Make Your Feet Happy

On many touring days, you spend far more time climbing than descending, but all of it is in your boots. Your feet swell on the skin track. The repetitive stride concentrates friction into hot spots and blisters. Plastic shells don’t breathe, so your feet sweat, and then the sweat freezes the moment you stop on a windy summit.

That’s what a good touring boot fit has to work against. Below is the exact process our bootfitters use at Cripple Creek Bike and Backcountry to get you into a boot that’s accurate, comfortable, and ready for long days in the mountains.

A Few Things to Know First

Boots come in full shell sizes. A 27.0 and a 27.5 use the exact same shell; only the liner or footbed may differ slightly. That’s why we stock boots by full shell size. Shell-size breaks vary by brand and model, including Scarpa. Ask a bootfitter which mondo sizes share the shell of the model you're considering.

Get a heat-moldable liner. Nearly every AT boot has one, and today’s liners are far better than they used to be. They can be molded multiple times and last much longer before needing replacement. If you're between sizes, molding can fine-tune the liner, but it cannot fix a shell that is fundamentally the wrong size.

Know the last. The last is the boot’s width across the forefoot, its widest point. Around 100mm is standard, ~98mm is narrow, and ~102mm+ is wide.

Plan for blisters. Extra weight, sweat, and a hard plastic shell can add up to blisters. A lighter, better-fitting boot reduces the risk. For extra insurance, pre-tape hot spots with Leukotape (duct tape works in a pinch).

Steps to Sizing an Alpine Touring Boot

1. Measure Your Feet

We start every boot fitting by measuring the length and width of both feet. Width matters as much as length, since it determines which boot lasts will work for you. We’ll also ask what kind of touring you plan to do (see our guide to choosing your ski touring setup), then pull a few boots that match.

2. Shell Fit

For each boot, we pull the liner and do a shell fit. Slide your socked foot into the empty shell, push your toes to the front, and check the gap behind your heel.

• ~1 finger: A snug, performance-oriented fit. More responsive on the descent, but less circulation and colder feet.
• ~2 fingers: A relaxed fit. More all-day comfort, less precision.
• ~1.5 fingers: The sweet spot for most touring skiers, regardless of ability.

Too tight and you risk pinched nerves, pain, and cold toes. Too loose and you’ll get heel lift, blisters, and sloppy skiing.

3. Liner Fit

Once the shell checks out, put the liner back in and try the boot on. Buckle from the top down. This seats your heel first, then the rest of your foot. The lower buckles should close easily with one finger. Cranking them down cuts off circulation across the top of your foot and leads to cold, numb toes.

You’re after confident comfort: secure but not restrictive, like a firm handshake. In ski mode, your toes should lightly touch the front of the liner. Flex your knee forward with your foot flat on the floor. If your toes pull back slightly from the front, the length is right.

4. Walk Mode and Ski Mode

Now switch to walk mode and walk around the shop. Minor liner pressure can sometimes improve with careful molding, but don't ignore sharp or persistent pain. Pay attention to major pressure points, or anything you know you couldn’t tolerate for a few hours on the skin track. If a boot has those, try another one until you find one that’s comfortable out of the box. For very wide feet or bunions, choose the most comfortable boot available and we’ll handle the rest with a liner mold and/or shell punch.

We often suggest skiing a new boot a few times before any custom work. Real days in the field reveal problem spots much better than a lap around the shop, and you may find you don’t need a mold at all, which can extend the life of some liners. Keep in mind that thicker liners change more when molded. Thin rando race liners barely change, so make sure those fit well out of the box.

5. Footbeds

Stock footbeds are flat, with little to no arch support. Some skiers are fine with that, but most aren’t. We strongly recommend either a supportive drop-in footbed or a custom Sidas footbed built at our Denver shop.

A good footbed supports your arch and helps your foot fill the boot’s volume the way it was designed to. The longer you spend in your boots, the more it matters: the right support can improve comfort and reduce unwanted movement in the boot. Most skiers benefit from at least a low-arch drop-in.

6. Book Your Fitting

Ready to find your boot? Book an appointment with one of our expert bootfitters.

Part of our Beginner's Ski Touring Guide. Guides are general education; product fit, compatibility, conditions and current manufacturer instructions should always be checked for your specific setup.