Ski Jacket Waterproof Ratings Explained: 10K, 15K, 20K

A ski jacket’s waterproof rating is the height of a column of water, in millimetres, that the fabric holds back before water starts to come through, so a 20,000 mm jacket resists twice the pressure of a 10,000 mm one. The Italian ski house Colmar publishes this figure on every rated piece, which makes its women’s designer ski jackets a useful way to learn the system. The Connected 3L Ski Shell Jacket in Disco Pink, rated 20,000 mm, is the clearest example at the top of the scale.

In short: the waterproof rating, written in mm and often shortened to 10K, 15K and 20K, tells you how hard water has to push to get through the fabric. Breathability, also written in K, tells you how much sweat vapour can escape the other way. A good ski jacket needs both, balanced for the weather and the way you ski.

What a water column rating measures

Picture a tall tube stood upright on a piece of fabric and slowly filled with water. The higher the water rises, the harder it presses down. At some height, drops appear on the underside. That height, in millimetres, is the water column rating. A fabric rated 10,000 mm holds back a column ten metres tall; one rated 20,000 mm holds back twenty metres.

Nobody skis under twenty metres of water, so why does the number matter? Because pressure on a jacket is not only falling snow. Kneeling in slush to fix a binding, sitting on a wet chairlift seat, the straps of a rucksack pressing on the shoulders, a fall into wet spring snow: each of these pushes water into the fabric far harder than rain does. A higher rating gives more margin in those moments.

Colmar uses three tiers on its women’s line this season: 10,000 mm, 15,000 mm and 20,000 mm. The house describes 10,000 mm as “suitable for heavy rain”, and 15,000 mm as “suitable for heavy rain, with barrier of up to 15,000 mm water column”. The table below lists how many styles at Coveti sit at each tier, with examples, and how Colmar describes the 20,000 mm level.

10K, 15K, 20K: the shorthand and the trap

Shops and skiers often say 10K when they mean 10,000 mm. It is a handy shorthand. The trap is that breathability is also written with a K, and Colmar uses the K form for breathability specifically: a Colmar piece rated 15,000 mm waterproof carries a separate 15K breathability rating. They are two different measurements that happen to share a number.

On Colmar’s women’s line the two figures generally move together. The table below pairs 10,000 mm with 10K, 15,000 mm with 15K and 20,000 mm with 20K. That makes the range easy to read, though it is worth knowing they are separate numbers if you compare against another house that pairs them differently.

What breathability means, and why it matters as much

A completely waterproof bag would keep the snow out and the sweat in. Skiing is hard work: a run through moguls, a walk up from the lift, a long traverse in soft snow, and the body pushes out a lot of moisture as vapour. If that vapour cannot leave, it condenses inside the jacket. You end up damp from the inside, and damp is what makes you cold on the next chairlift.

Breathability is the measure of how much water vapour the fabric lets through in a set time. Higher is better, and brands write it in thousands, hence 10K, 15K, 20K. Different houses measure it in different ways, so the safest comparison is within one brand’s range, which is exactly where Colmar’s published figures help.

Colmar’s own wording gives a sense of scale. It describes 10K breathability as “suitable for moderate hikes and regular outdoor activities”, and rates 15K as excellent for sports. If you ski hard all day, sweat on the climb back to the car, then sit still on a long lift, breathability is the number to look at second, right after the waterproof rating.

Water-repellent finish against a rated membrane

Two different things keep water out of a ski jacket, and they are easy to confuse. The first is a water-repellent finish on the outer fabric. It makes water bead up and roll off, so the face fabric does not soak through and get heavy. It is a surface treatment, and it wears down with use and washing. Colmar lists a water-repellent finish “developed without the use of PFOAS and PFOS” on most of its rated pieces.

The second is the waterproof barrier, a membrane bonded to the fabric. This is what the water column rating describes. The finish is the first line of defence; the membrane is the one that holds when the finish is tired and water is being pressed in.

Some Colmar pieces have a finish but no membrane rating. The Austrian National Team Quilted Jacket in Indian Red and Black, $680 at Coveti, is one: Colmar lists a water-repellent finish and a Medium warmth level, and publishes no water column. That makes it a jacket for dry cold days, the walk to the lift, and evenings in the village, rather than a storm. In the table below, 22 styles sit in this unrated group. Several of them are fleeces and base layers that are worn under a shell and were never meant to face the weather.

What a 3L shell is

Two of the jackets at the top of Colmar’s scale carry 3L in their names. A three-layer shell bonds the outer fabric, the waterproof membrane and a thin inner layer into a single piece of cloth. The result is durable and light, because nothing hangs loose inside.

The Connected 3L Ski Shell Jacket in Disco Pink, $1,060 at Coveti, is rated 20,000 mm and 20K but only Light for warmth, with a RECCO reflector. It is a shell in the strict sense: weather protection, with the warmth coming from what you wear underneath. The Padded 3L Ski Shell Jacket in Incense White, $1,020 at Coveti, has the same 20,000 mm and 20K ratings with a Medium warmth level and a Comfort fit. Same barrier, more insulation built in.

Warmth is a separate rating

Waterproofing and warmth are not the same thing. A jacket can be fully rated against water and still cold, as the Connected shell shows. Colmar publishes a third figure for this, a warmth level on four steps: Light, Medium, Warm and Very Warm. The second table below gives Colmar’s description of each step and how many pieces at Coveti carry it.

Warmth comes from insulation, and Colmar names it on many product pages. The Shaped Ski Jacket with Faux Fur in Black, $1,290 at Coveti, is rated 20,000 mm, 20K and Warm, with 140 g Repreve wadding and a graphene lining. The Mirea Glossy Ski Down Jacket in Black, $1,020 at Coveti, goes the other way: a lower 10,000 mm and 10K rating, but down insulation and the top Very Warm level. Fusalp grades warmth on its own scale, and our explainer on Fusalp warmth levels is a useful companion if you are comparing the two houses.

Colmar pieces as worked examples

The quickest way to understand the scale is to read a few real pieces against it.

At 20,000 mm and 20K, the Glam Padded Ski Trousers in Black, $660 at Coveti, are Colmar’s top-rated padded trousers: Warm, with 80 g Clomax padding, a graphene lining and a RECCO reflector. Trousers take more water pressure than jackets, because you sit and kneel in them, so a high rating on the lower half is money well spent.

At 15,000 mm and 15K, the Niseiko Ski Jacket in Black and White, $790 at Coveti, is rated Warm with a Regular fit. The Austrian National Team Ski Jacket in Indian Red, $1,110 at Coveti, sits in the same tier with 150 g Repreve wadding. The middle tier covers the most ground: proper protection for ordinary Alpine weather, with breathability Colmar calls excellent for sports. The Prize Padded Ski Trousers in Black, $610 at Coveti, are a matching 15,000 mm, 15K and Warm on the legs.

At 10,000 mm and 10K, the Dressy Softshell Ski Trousers in Black, $520 at Coveti, are a softshell rated Medium, built to stretch with the body. The Puffy Padded Gilet in Incense White, $640 at Coveti, is a down gilet rated Very Warm with the same 10,000 mm barrier. Neither is a weak piece. They are pieces for days when movement and warmth matter more than a storm.

For full style-by-style detail, see our guides to Colmar ski jackets and Colmar ski trousers and salopettes.

How to choose by resort and by how you ski

Start with the weather. Resorts near freezing, low villages, and spring weeks bring wet snow and sleet, which press water into fabric hard. That is where 15,000 mm and 20,000 mm earn their keep. High, cold resorts in midwinter tend to bring dry snow that brushes off, so a 10,000 mm piece with good insulation can be the better buy, because warmth matters more than barrier.

Then think about how you ski. A skier who works hard, hikes for fresh snow and runs warm should look at breathability first and keep the built-in warmth low, then add layers. Our guide to how to layer for skiing sets out that system, and Colmar’s mid-layers are covered in Colmar fleeces and base layers. A skier who feels the cold, takes long lifts and stops often should choose a Warm and Very Warm piece and accept a mid-tier rating if the insulation is right.

Finally, match top and bottom. A 20,000 mm jacket over unrated trousers leaves the half of you that sits on the chairlift exposed. One-piece suits solve the problem by design, and our guide to Colmar ski suits covers the rated options. For a broader view across houses, see our edit of the best women’s ski jackets.

Waterproof ratings around the world

US buyers skiing the Rockies usually meet cold, dry snow, where warmth and breathability count for more than the highest barrier. The 15,000 mm tier is a sound default. Colmar’s IT 42 is a US 6, and prices at Coveti are shown in US dollars.

UK buyers often travel to the Alps for half-term and Easter, when lower slopes turn wet in the afternoon. A 15,000 mm to 20,000 mm jacket and matching trousers are worth it there. A UK 10 is IT 42 at Coveti. EU buyers in France, Germany, Austria and Italy can read Colmar’s size straight across: IT 42 is FR and ES 38 and DE 36. The same rating logic applies, with the warmer tiers favoured for high resorts in January.

GCC buyers who ski at Ski Dubai, an indoor slope, need warmth more than any water barrier, so a 10,000 mm piece is plenty there. For travel to the Alps, Japan and the Rockies, a higher rating and a proper layering system make sense, because outdoor weather changes through the day in a way an indoor slope never does. Coveti is London-based, every piece is 100% authentic, and we ship worldwide.

The full range of rated pieces is on the Colmar brand page at Coveti. The tables below set out Colmar’s three tiers and its four warmth levels with the house’s own wording.

How we measured: ratings, warmth levels and the descriptions are the wording Colmar publishes on each product page (colmar.com, read on 1 November 2026). Colourways and prices are the Coveti catalogue on the same date. Where Colmar does not publish a figure, the cell says so. Nothing is estimated.

Frequently asked questions

Is 10,000 mm waterproof enough for skiing?

Yes, for most resort skiing in dry, cold snow, 10,000 mm is enough, and Colmar describes it as suitable for heavy rain. It has less margin when you sit and kneel in wet snow, so for spring weeks and low resorts a 15,000 mm to 20,000 mm piece is the safer choice, especially on trousers.

What does 20K mean on a Colmar ski jacket?

On a Colmar product page, 20K is the breathability rating, the measure of how much sweat vapour can escape through the fabric. The waterproof rating is given separately in millimetres. On Colmar’s women’s line, 20K is paired with 20,000 mm, so a 20K jacket such as the Connected 3L Ski Shell is at the top of both scales.

Do Colmar jackets without a rating keep out snow?

Colmar pieces without a membrane rating, such as the Austrian National Team Quilted Jacket, rely on a water-repellent finish, which sheds light snow and helps in dry cold. They are not built to hold back water under pressure. For a stormy day, choose a piece with a published water column rating of 10,000 mm and above.

Is a higher waterproof rating always better?

Not always. A higher rating gives more margin against water pressure, but warmth and breathability matter just as much on the slope. A 20,000 mm shell rated Light can feel cold without layers, while a 10,000 mm down jacket rated Very Warm suits a cold, dry day. Choose by the conditions you ski in.

What is the difference between waterproof and water-repellent?

Water-repellent describes a surface finish that makes water bead and roll off the fabric, and it wears down over time. Waterproof describes the membrane underneath, rated by its water column in millimetres. Most of Colmar’s rated pieces carry both, with a finish developed without the use of PFOAS and PFOS over a 10,000, 15,000 and 20,000 mm barrier.

How should I care for a waterproof ski jacket?

Follow the label on each piece. On most Colmar pieces that means a machine wash at a maximum of 30 degrees C, no bleach, no tumble drying and no dry cleaning. Regular gentle washing keeps the face fabric clean, which helps the water-repellent finish do its job, and detachable faux-fur trims should come off first.