Waterproof & Breathability Ratings Explained | Snow Outerwear Guide

The first number is waterproofing in millimetres. The second is breathability in grams. A 10K/10K jacket is 10,000mm waterproof and 10,000g breathable. For Australian snow, 15K is the number most people should be buying.

Most people nod along at those numbers without knowing what they mean, then wonder why their bargain jacket left them soaked by lunch. Here is what they measure, what each rating actually survives, and the real difference between a rated jacket and a cheap DWR-coated one.

The short version

First number = waterproofing in millimetres. Second number = breathability in grams
Minimum for snowboarding: 10K
Sweet spot for Australian snow: 15K to 20K
Breathability for most riders: 10K to 15K, higher if you hike or run warm
Check taped seams too: a fully taped 10K jacket beats an untaped 20K one
Avoid: DWR-coated jackets with no rated membrane. The coating wears off within a season
If you are still unsure: 15K/15K fully taped handles almost everything an Australian season throws at you

What we cover: The two numbers · What each rating means · Breathability · Cheap vs rated · Taped seams · FAQ

What do the two numbers mean?

Outerwear is rated on two separate measurements, usually written as a pair:

Waterproofing, measured in millimetres (mm), often written as 10K (10,000mm), 15K, 20K and so on. This is the first number.
Breathability, measured in grams (g), also written 10K, 15K, 20K. This is the second number.

So a 10K/10K jacket is 10,000mm waterproof and 10,000g breathable. A 20K/20K jacket is 20,000mm and 20,000g. They measure two completely different things, and both matter. A jacket can be very waterproof and barely breathable, or the reverse. The best outerwear balances the two.

The waterproof number comes from a real test: a sealed tube of water is placed over the fabric, and the mm figure is how tall the column of water gets before it leaks through. Higher number, more pressure the fabric resists.

That matters because you put pressure on fabric constantly when riding — sitting on wet snow, kneeling, the weight of a pack, leaning against a chairlift. Each of those drives water through a low-rated fabric.

What each waterproof rating actually means

Rating	What it handles
0 to 5K	Light rain, dry snow, low activity. Wets through under any real pressure. Department-store territory.
10K	The practical minimum for snowboarding. Average resort conditions, light sitting.
15K	Solid all-rounder. Wet Australian snow, sitting, falls, a full day out.
20K	Serious wet-weather protection. Sustained pressure and the heaviest conditions.
28K and above	Premium shells and hardwear. More than most resort riders need.

What does 5K waterproof mean?

5,000mm. It repels light rain and dry snow and nothing more. Sit down on a wet chairlift and you will feel it come through. This is the rating on most department-store and fashion snow jackets, and it is the main reason people end up cold and wet on day one.

What does 10K waterproof mean?

10,000mm, and it is the practical floor for snowboarding. It handles an average resort day, light snow and short sits. Fine if you ride a handful of fair-weather days a year.

It is a floor, not a margin. On a wet Australian afternoon, or a day where you fall a lot and sit a lot, 10K will start to wet out.

What does 15K waterproof mean?

15,000mm, and it is the rating we recommend most often. It handles wet, heavy Australian snow, a full day of sitting and falling, and weather that turns halfway through the afternoon.

The jump from 10K to 15K is the biggest real-world improvement in the whole range, and the price difference is usually smaller than the jump from 15K to 20K. If you buy one number off this page, buy this one.

What does 20K waterproof mean?

20,000mm, the high end of mainstream snow outerwear. It resists sustained pressure and the wettest, heaviest conditions you will ride in.

Worth it if you ride in everything, ride most weekends, or hike and sit in wet snow. For a few fair-weather days a year, 15K does the job for less.

What about 28K and above?

Premium shells, often GORE-TEX Pro or equivalent. Built for sustained alpine and backcountry use. More than most resort riders need, and you are usually paying for durability and construction as much as the number.

For Australian conditions specifically: 10K is the floor, 15K to 20K is the sweet spot. Our snow is wet and heavy compared to Japan or North America, so you spend more of the day in contact with moisture and the rating works harder here than the same jacket would overseas.

What does the breathability number do?

Breathability measures how much water vapour, meaning your sweat, the fabric lets escape over 24 hours. The higher the number, the more sweat moves out before it condenses inside your jacket and leaves you clammy.

This is the number people ignore and regret. Snowboarding is high-output: hiking to a side hit, skating to the lift, riding hard. If your jacket does not breathe, the sweat has nowhere to go, condenses on the inside, and you get just as wet as if rain came through. A waterproof jacket that does not breathe makes you wet from the inside.

5K to 10K: fine for low-output, casual riding. Will feel clammy if you push hard.
10K to 15K: good for most riders. Keeps up with normal resort activity.
15K to 20K and above: for high-output riders, hikers and anyone who runs warm. Moves sweat fast.

Pit zips and vents help here too. Even a moderately breathable jacket with good venting handles output well, because you can dump heat manually when you are working hard.

Why does a rated jacket beat a cheap waterproof one?

A basic jacket from a department store or discount chain is usually DWR-coated only, with no rated membrane underneath. DWR (Durable Water Repellent) is a surface treatment that makes water bead off. That is it. It works for the first few wears, in light conditions.

The problem is that DWR is only a surface coating. Once it wears off, and it wears off fast, often within a season, the fabric underneath has no waterproofing at all. There is no membrane doing the real work. The jacket wets out, soaks through, and you are cold and wet. There is also usually no rated breathability, so even before it wets out you are sweating on the inside.

A properly rated jacket has a waterproof-breathable membrane bonded into the fabric, and that is what the numbers describe. The DWR on top is just the first line of defence; the membrane underneath is the real barrier, and it does not wear off.

Put simply: a cheap jacket relies on a coating that fails, a rated jacket relies on a membrane that lasts. Buy once, buy right. A proper jacket is dry for years, a cheap one is dry for weeks. If you want the premium end of that membrane story, read what GORE-TEX actually is.

What are taped seams and why do they matter?

A high waterproof rating means nothing if water pours through the stitching. Every seam is thousands of needle holes. Quality outerwear has taped seams, a waterproof tape heat-sealed over the stitching on the inside.

Fully taped: every seam sealed. The standard for serious wet-weather outerwear.
Critically taped: only the most exposed seams, such as shoulders and hood, are sealed. A cost-saving compromise, fine for fair weather but not for heavy days.
Untaped: no seam sealing. Common on cheap jackets, and a guaranteed leak point regardless of the fabric rating.

Always check seam taping alongside the rating. A 20K jacket with untaped seams will leak before a 10K jacket that is fully taped.

Frequently Asked Questions

What does 10K/10K mean on a snowboard jacket?

The first number is waterproofing in millimetres, the second is breathability in grams. So 10K/10K means 10,000mm waterproof and 10,000g breathable. They measure two different things and both matter, because a jacket can be waterproof and barely breathable, or the reverse.

What does 20K/20K mean?

20,000mm waterproof and 20,000g breathable. It is the high end of mainstream snow outerwear and handles sustained wet conditions and high-output riding without wetting out from either direction.

Is 10K waterproof enough for snowboarding?

Yes for fair-weather resort riding, but it is the floor rather than a comfortable margin. 10K handles average conditions and light sitting. If you ride in everything, or spend time sitting and falling in wet snow, step up to 15K or 20K.

Is 15K waterproof good for snowboarding?

Yes, and it is the rating we recommend most often for Australian conditions. 15K handles wet heavy snow, sitting, falls and a full day out without wetting through, and it costs far less than 20K.

Is 20K waterproof worth it?

Worth it if you ride in everything, ride most weekends, or hike and sit in wet snow. For a handful of fair-weather resort days a year, 15K does the job for less money.

What waterproof rating do I need for snowboarding?

10K is the practical minimum and 15K to 20K is the sweet spot for Australian conditions. Our snow is wet and heavy, so you spend more of the day in contact with moisture and the rating works harder here than the same jacket would in Japan or North America.

What does the breathability rating do?

It measures how much sweat vapour escapes over 24 hours. If a jacket does not breathe, sweat condenses inside and you get just as wet as if water came through. 10K to 15K suits most riders, 15K to 20K plus suits high-output riders and hikers.

Why is a cheap waterproof jacket not good enough?

Cheap jackets are usually DWR-coated only, with no rated membrane underneath. DWR is a surface treatment that wears off, often within a season, leaving no waterproofing at all. A rated jacket has a membrane bonded into the fabric that does not wear off.

What are taped seams and do they matter?

Taped seams are waterproof tape heat-sealed over the stitching inside the jacket. They matter enormously: a 20K jacket with untaped seams will leak before a 10K jacket that is fully taped, because every seam is thousands of needle holes.

Still not sure?

Tell us where you ride and how hard, and we will point you at the right rating rather than the most expensive jacket. Call (03) 9421 2293 or come into 435A Bridge Road, Richmond. Free shipping Australia-wide on orders over $90.

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