What Do Jacket Ratings Actually Mean? Understanding Your Winter Wear
If there’s one thing I’ve learned from living in a cold climate, it’s that not every jacket is created equal.
That’s a good thing, since we need different jackets for different types of weather, but you can’t always tell at a glance just how effective a jacket is going to be in different conditions.
It would be a lot easier to do our winter shopping if we just wanted waterproof jackets, but that’s actually a really bad idea.
An entirely waterproof jacket would keep all the moisture out, but it would also keep all of your moisture in.
You can probably imagine what it would be like to do absolutely anything active if you were wearing a waterproof plastic bag… not very pleasant.
That’s why jackets are rated on 3 different scales — water resistance, breathability, and temperature.
Water resistance and breathability are, in a sense, dueling forces.
To be able to let water out, the jacket must be able to let water in — but you really only want one of those to happen.
- Water Resistance
This is measured in millimeters per square inch of water pressure.
If you were to take a 1-inch square tube and press it firmly to a jacket rated 10k, you could fill it with 10,000 mm of water before it started leaking through.
I know that’s hard to picture, but 10,000 mm is about 32 feet or 10 meters.
That is a lot of water.
2. Breathability
Measuring breathability is a little different because the moisture is in the form of water vapor, not liquid water.
This is measured by how much water vapor can move from the inside to the outside of 1 square meter of fabric, over a 24 hour period.
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So a jacket with a rating of 10k for breathability would be able to move 10 kg, or 22 lbs of water from inside to out, per square meter per day.
That’s a lot of math and numbers, but we’ll get to what it all means in just a minute, I promise.
3. Temperature
The temperature rating of a jacket doesn’t have too much to do with the other ratings, but it is a good indicator of how well insulated it is.
These are fairly easy to understand, a jacket rated for -20 should keep you warm in -20 weather.
Temperature ratings can be a bit subjective though, and a lot will also depend on the windchill, your body type, and activity level.
Putting It All Together
Finally, the moment we’ve all been waiting for — how to choose the right jacket for you.
Your local weather and what you plan to do while wearing your jacket will be the big factors to consider.
Obviously the colder the weather, the lower the temperature you want your jacket to be rated for.
To find the right level of water resistance and breathability, consider how wet your weather is, how often your jacket gets soaked, and how active you plan to be.
Water Resistance — A jacket with 10k water resistance can handle a fair amount of light rain or moderate rain for a short amount of time, 15k can handle a decent length of time in moderate rain, and a few minutes in heavy rain.
20k water resistance should keep you dry even in heavy rains for a decent length of time — though they’re still not a raincoat, and you should remember they aren’t actually waterproof.
Breathability — For breathability, up to a 10k jacket is great if you’re taking short trips outside and mostly walking.
You may want to consider a 15k jacket if you plan on doing any kind of regular physical activity, and a 20k if you’re very active.
Whether you need a light spring jacket, or a 20k/20k extreme coat is something you’ll have to decide on your own.
Personally, I always go with a slightly higher rating than I need, because I’d rather be safe than cold and wet.
Knowing what the ratings mean is half the battle though, so hopefully now you’re well armed.
Stay warm!
