Waterproof & Breathability Ratings Explained | Snow Outerwear Guide

Every piece of snow outerwear carries two numbers, something like 10K/10K or 20K/15K. Most people nod along without knowing what they mean, then wonder why their bargain jacket left them soaked by lunch. This guide explains what those ratings measure, what each tier actually survives on the mountain, and the real difference between a properly 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 · Waterproof rating · 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. 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.

What waterproof rating do you actually need?

The waterproof rating 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 can get before it starts to leak through. Higher number, more water pressure the fabric resists before it gives up.

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

Rating	What it handles
0 to 5K	Light rain, dry snow, low activity. Wets through under any real pressure or a wet day. This is department-store territory.
10K	The practical minimum for snowboarding. Handles average resort conditions and light sitting. Fine for fair-weather riders.
15K	Solid all-rounder. Handles wet Australian snow, sitting, falls and a full day out without wetting through.
20K and above	Serious wet-weather and all-day protection. Resists sustained pressure and the wettest, heaviest conditions. The standard for riders who are out in everything.

For Australian conditions specifically, 10K is the floor and 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 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.

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.

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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