Kids' ski boot size chart, and how to measure a foot properly
Ski boots are sized in Mondopoint, which is just the length of the foot in centimeters. That makes them easier to understand than shoes and much less forgiving.
By Sawyer V. · Published
We have not tested this gear. Everything below is compiled from published specifications and published safety standards, and the arithmetic is public so you can check it. This page carries affiliate links: if you buy through one we earn a commission at no extra cost to you, and it does not change the order of the picks. Full disclosure.
The short answer
Ski boots are sized in Mondopoint, which is the length of the foot in centimeters. Measure your child’s foot from heel to longest toe in millimeters, divide by ten, and that number is their Mondopoint size. A 210 mm foot is a 21.0 Mondopoint boot, which is around a US kids 2. Do not add growing room beyond half a size.
| # | Pick | Best for | Score | Price |
|---|---|---|---|---|
| 1 | Darn Tough Alpine Over-the-Calf Lightweight Ski Socks The one piece of ski gear worth buying before anything else | $2 a dayon snow | 6.4/10 | $30.64 - View on Amazon |
| 2 | Smartwool Ski Zero Cushion Over-the-Calf Socks A boot that already fits, where any extra bulk makes it worse | $1.93 a dayon snow | 5.9/10 | $30.00 - View on Amazon |
Prices last verified October 19, 2026. Prices move constantly; the figure on Amazon at the moment you click is the real one.
What Mondopoint actually is
Every ski boot in the world, in every brand, is labeled with the same number: the length in centimeters of the foot it is built for. A boot marked 22.5 is built for a 225 mm foot. That is the whole system.
This is genuinely better than shoe sizing, because it removes the brand guesswork from the length. It does not remove the width guesswork: two boots at the same Mondopoint size can be noticeably different in volume, and that is the part a shop solves and a website cannot.
The chart
| Foot length | Mondopoint | Approx. US kids shoe | Rough age guide |
|---|---|---|---|
| 160 mm | 16.0 | 9C | 3 to 4 |
| 170 mm | 17.0 | 10.5C | 4 to 5 |
| 180 mm | 18.0 | 11.5C | 5 to 6 |
| 190 mm | 19.0 | 12.5C | 6 to 7 |
| 200 mm | 20.0 | 1Y | 7 to 8 |
| 210 mm | 21.0 | 2Y | 8 to 9 |
| 220 mm | 22.0 | 3.5Y | 9 to 11 |
| 230 mm | 23.0 | 4.5Y | 11 to 13 |
| 240 mm | 24.0 | 6Y | 12 and up |
| 250 mm | 25.0 | 7Y | 12 and up |
Measuring a foot, with a piece of paper
- Put a sheet of paper on a hard floor with one edge against a wall. Carpet gives a wrong reading because the heel sinks.
- Have the child stand on the paper with their heel against the wall, wearing the sock they will ski in. Standing matters: a foot spreads and lengthens under body weight, and a measurement taken sitting down produces a boot that is too short.
- Mark the paper at the end of the longest toe, which is not always the big toe.
- Measure from the wall edge to the mark in millimeters. Do both feet and use the larger one; most people have one foot slightly longer.
- Divide by ten. That is the Mondopoint size to start from.
How much growing room, honestly
Half a size. Not one, and definitely not two.
The reason is that a ski boot is a steering control, not footwear. Turning a ski works by rolling the boot onto its edge, and the boot only transmits that movement if it is holding the foot. In a boot with room in it, the foot slides instead, the ski does not respond, and the child spends the day fighting the equipment and concluding they are bad at skiing.
- Correct: toes brushing the front of the liner when standing upright, and pulling back off the front when the child bends their knees.
- Too big: the heel lifts when they bend their knees, or you can get a finger down behind the heel easily.
- Too small: toes curled or jammed hard against the front even with knees bent.
Which is why we usually say rent these
Half a size of allowance and a growing child are in direct conflict, and that conflict is what makes boots the strongest rental case in this entire category. Many shops and resorts run seasonal lease programs that swap sizes mid-season for free when a foot grows out of a boot, which no purchase can match.
The boots-specific arithmetic is here, and the general buy versus rent page covers the rest of the kit. This is one of several places on this site where the honest answer earns us nothing.
One thing that changes the fit
Measure and try boots in a thin ski sock, never a thick one. A thick sock takes up space the boot needs, restricts circulation and makes feet colder rather than warmer, and it is the most common reason a child says their boots hurt. Here is the full explanation, which is the single cheapest fix on this site.
If you are sizing an adult too
The system is identical, the numbers are just bigger, and the shell width matters more as feet get larger. The adult boot size chart is here, including the flex numbers that appear on adult boots and not on children’s.
Every pick, with the working
Each entry shows the published inputs, the axis scores they produce, and what you give up. The order is the computed order, not a commercial one, and the arithmetic is open underneath each score.
1 · The one piece of ski gear worth buying before anything else
Darn Tough Alpine Over-the-Calf Lightweight Ski Socks
The only item in this entire ledger with an unconditional lifetime guarantee. It is a $30 sock that the maker will replace forever, which over any realistic number of ski days is the cheapest thing on the site.
- Published price
- $30
- Cost per day on snow
- $2 a day
- Amortized over
- 3 seasons (15 days)
- Certified to
- Not published
- Published sizes
- S through XL
- Warranty
- Unconditional lifetime guarantee
What it gets right
- Unconditional lifetime guarantee, published without qualifying conditions
- Lightweight merino, which is correct for a modern ski boot: a thick sock makes boots colder, not warmer
- Over-the-calf length, so the boot cuff never touches bare skin
What you give up
- $30 for one pair of socks reads as absurd until the replacement policy is read
- Lightweight is the right choice but feels wrong to anyone expecting a thick ski sock
The working behind the 6.4
- Cost per day on snow: 9.6
- $30 over 3 seasons at 5 days each = 15 days = $2 a day
- Published protection: not scored
- Socks carry no protective standard, so this axis does not apply.
- Size availability: 5.1
- 4 published sizes (5.1 of 8.5); no continuous adjuster published (+0); range: S through XL
- Warranty and support: 2.0
- no published term (0 of 6); no published crash replacement (+0); repair or replacement parts published (+2)
Axes with unpublished inputs are dropped and the remaining weights re-normalized, so a product is not punished for a manufacturer’s silence. Specifications compiled September 3, 2026 from Darn Tough published specifications.
2 · A boot that already fits, where any extra bulk makes it worse
Smartwool Ski Zero Cushion Over-the-Calf Socks
Zero cushion is not a compromise, it is the point: in a boot fitted properly there is no room for padding, and every millimeter of sock is a millimeter of lost contact with the shell.
- Published price
- $28.95
- Cost per day on snow
- $1.93 a day
- Amortized over
- 3 seasons (15 days)
- Certified to
- Not published
- Published sizes
- S through XL
- Warranty
- Limited lifetime warranty
What it gets right
- Zero cushioning, which is the correct construction for a fitted ski boot
- Limited lifetime warranty published
- Merino blend, so it stays warm damp and does not smell after three days
What you give up
- The limited lifetime warranty is a narrower promise than Darn Tough's unconditional one
- Anyone whose boots are slightly too big will find zero cushion uncomfortable
The working behind the 5.9
- Cost per day on snow: 9.7
- $28.95 over 3 seasons at 5 days each = 15 days = $1.93 a day
- Published protection: not scored
- Socks carry no protective standard, so this axis does not apply.
- Size availability: 5.1
- 4 published sizes (5.1 of 8.5); no continuous adjuster published (+0); range: S through XL
- Warranty and support: 0.0
- no published term (0 of 6); no published crash replacement (+0); no published repair route (+0)
Axes with unpublished inputs are dropped and the remaining weights re-normalized, so a product is not punished for a manufacturer’s silence. Specifications compiled September 3, 2026 from Smartwool published specifications.
Prices last verified October 19, 2026. Prices move constantly; the figure on Amazon at the moment you click is the real one.
Questions people actually ask
How do I convert shoe size to ski boot size for a child?
Do not, if you can avoid it: measure the foot in millimeters and divide by ten to get the Mondopoint size. Shoe sizes vary by up to a full size between brands, and a ski boot is sized far too precisely to absorb that.
What Mondopoint is a US kids size 2?
Around 21.0, which corresponds to a 210 mm foot. Treat that as a starting point for the shelf rather than an order: measure the actual foot before buying.
Should kids ski boots be tight?
Snug, with the toes brushing the front of the liner when standing upright and pulling back when the knees bend. The heel should not lift. Pain in one spot is a shape problem, not a size problem, and means a different boot.
Can my child wear ski boots a size big so they last?
Half a size at most. A boot with room in it stops working as a steering control, which is the main reason children get frustrated learning. If growth is the problem, a seasonal lease with free size swaps is the right answer.
Do ski boots come in different widths for children?
Less than adult boots do. Junior boots are generally built on a more generous last so a range of foot shapes fits, which is one reason a child’s boot is easier to buy than an adult’s. It is still worth having a shop check the fit.