What 10K/5K Means on a Kids Snow Jacket
By Dakine | Backpacks, Luggage, Surf, Snow, & Bike Gear Since ... | Published: 2026-10-31
Category: How-to Guides
10K/5K is not a single waterproof score—it's two separate ratings for water resistance and breathability. Here's what they mean for kids' snow jackets and when they're enough.
Quick answer
10K/5K means the jacket fabric is rated to resist 10,000 mm of water pressure and to let out 5,000 grams of moisture vapor per square meter per day. Those are two separate lab ratings, not a combined score—and for most kids' resort skiing, 10K waterproofing with 5K breathability is a sensible, practical choice.
The two numbers measure different things
The first number (10K) is about keeping outside moisture out. It tells you how much water pressure the fabric can withstand before water starts to push through. The second number (5K) is about letting inside moisture escape—the sweat vapor a kid generates while skiing or playing in the snow. A jacket can be highly waterproof but poorly breathable, or the reverse, so reading both numbers separately matters.
This is why a 10K/5K jacket isn't simply 'half as good' as a 20K/20K jacket. It's tuned for a different balance: solid wet-snow protection with moderate breathability, which suits stop-and-go youth skiing better than a single overall score suggests.
Why 5K breathability is usually enough for kids
Kids tend to ski in shorter bursts with more breaks than adults, and they're often not pushing a sustained aerobic pace for hours. That stop-and-go rhythm produces less continuous sweat vapor than a hard-charging adult run. A 5K breathability rating is designed for that moderate output, especially when the jacket has mechanical venting to dump heat quickly.
The trade-off: if your child runs hot, skis aggressively all day, or tours rather than rides lifts, 5K may feel clammy on warm spring days. In that case, look for a higher breathability number or rely on pit vents and layering rather than expecting the fabric alone to manage moisture.
Don't overlook construction details
A waterproof rating only describes the fabric—it doesn't cover seams, zippers, or cuffs. Critically taped seams, a fixed powder skirt, and a jacket-to-pant attachment system do a lot of the real-world work of keeping snow out. A 10K jacket with those features can outperform a higher-rated shell with exposed seams.
Similarly, wrist gaiters and hem adjustment keep snow from riding up sleeves and waist, which matters more on a kids' jacket than chasing a bigger number on the hangtag.
Verdicts on common 10K/5K claims
- “10K/5K is one combined waterproof score.”: False. 10K is water resistance and 5K is breathability—two separate ratings. Read them independently: 10K tells you how much water pressure the fabric resists, and 5K tells you how much moisture vapor it lets out. Check both numbers on the hangtag; a high first number with a low second can still feel sweaty.
- “5K breathability is too low for kids.”: Not necessarily. For typical stop-and-go youth resort skiing, 5K breathability paired with mechanical venting is often adequate. It may fall short for aggressive all-day skiers or warm spring conditions. Match breathability to how hard and how long your child actually skis, not to an adult's output.
- “A higher waterproof number always means a better kids' jacket.”: Only if the construction supports it. Critically taped seams, powder skirt, wrist gaiters, and hem adjustment keep snow out in ways the fabric rating alone doesn't measure. A 10K jacket with those features can be more protective in practice than a higher-rated shell without them. Look for taped seams and snow-blocking features alongside the rating.
- “10K/5K is only for mild weather.”: 10K waterproofing is built for sustained snow contact—not just flurries. It's a common, capable rating for resort skiing in wet snow. The limit is breathability during high-output activity, not waterproofing in typical winter conditions. For wet resort days, 10K waterproofing is sufficient; manage sweat with layers and vents.
Product facts
- Siphon Youth Jacket 10K/5K - Blue Blossom: Siphon Youth Jacket 10K/5K - Blue Blossom has a 10K/5K rating, critically taped seams, and mesh-lined venting. The 10K waterproofing plus taped seams covers wet resort snow, while mesh vents let kids dump heat on warmer lift rides without needing a higher breathability rating.
Siphon Youth Jacket 10K/5K - Blue Blossom
