For lift-served resort skiing, 190 to 250 gsm. For ski touring or anything involving climbing, 150 to 190 gsm. The gap between those recommendations is larger than most people expect, and it exists because the two activities produce completely different amounts of body heat in identical weather. Start from our base layers and match the weight to how you ski.
Resort and touring are different problems
A resort day is mostly sitting still. You ride a lift in the wind, ski down for a few minutes, and repeat. Heat output is low for most of the day, and the cold arrives while you are stationary and exposed. You want insulation.
A touring day is mostly climbing. You generate serious heat for hours, then stop at the top and cool rapidly while transitioning. You want moisture management and a layer that does not soak through, because a saturated base layer at a windy col is genuinely dangerous.
| How you ski | Conditions | Weight | Notes |
|---|---|---|---|
| Resort, mild | −5°C and above | 190 gsm | Add a mid-layer rather than a heavier base |
| Resort, cold | −5 to −20°C | 235–260 gsm | Long body and high collar matter here |
| Resort, extreme | Below −20°C | 260–300 gsm | Consider two layers instead of one very heavy one |
| Touring, any | Most conditions | 150–190 gsm | Bring a dry layer for the summit |
| Kids at the resort | Any | 190–250 gsm | Kids chill faster when stationary |
Why heavier is not automatically warmer on the hill
Ski clothing is a system, and the base layer is the smallest contributor to warmth in it. Your shell blocks wind, your mid-layer provides most of the insulation, and the base layer manages moisture at skin level. Going from 190 to 250 gsm changes less than adding a proper mid-layer would.
Overshooting the weight causes real problems. A heavy base layer under a warm mid-layer and a shell will overheat you on the first sustained run, and the sweat you produce then chills you on the next lift. That cycle is more uncomfortable than starting slightly cool.
Tops and bottoms want different weights
Legs generate substantial heat while skiing and are already covered by insulated ski pants. Most people are better served by a lighter bottom than top — a 150 or 190 gsm legging under ski pants is usually enough even when the top is 250.
Overheated legs are also harder to fix mid-day. You can unzip a jacket on a lift; you cannot remove a base layer bottom without going inside. Erring light on the bottom is the safer mistake. Browse base layer bottoms for the lighter weights.
What goes over it matters more
Before adding base layer weight, check the rest of the system. A shell that does not block wind will undo any base layer. A mid-layer that is too bulky restricts movement and traps sweat. Vents you never open are insulation you cannot adjust.
Our guides to what to wear under a ski jacket and under ski pants cover assembling the layers around the base.
Cold days, warm days and the ones in between
A single base layer cannot cover a season that runs from spring slush to a January cold snap. Most people end up with two: a 190 gsm for the majority of days and something heavier for the coldest fifth of them.
If you would rather own one, buy the lighter one and add a mid-layer for cold days. Adding insulation over a light base is easy; removing warmth from a heavy base is impossible once you are on the hill. The asymmetry favours going light and layering up.
Spring skiing deserves its own mention. Wet snow, strong sun and warm afternoons make a heavy base layer miserable by noon, and a soaked base layer is cold on the last lift. A 150 gsm layer with a vented shell handles spring far better than winter kit does.
What about a second layer on the coldest days?
Two thin layers usually beat one thick one. They trap air between them, they can be adjusted independently, and one can be removed at lunch. A 150 gsm top under a 190 gsm top is warmer than a single 300 gsm layer in most conditions and considerably more flexible.
The limit is fit. Two layers plus a mid-layer plus a shell can compress into something that restricts movement and, worse, compresses the air that provides the insulation. If the system feels tight, it is working against itself.
Socks are the exception to "warmer is better"
Thicker ski socks make feet colder, not warmer. A ski boot is a fixed volume, and a thick sock compresses the foot and restricts circulation. Blood flow is what keeps toes warm, and a thin sock in a well-fitted boot outperforms a thick one in the same boot.
Buy a thin-to-midweight merino ski sock, wear exactly one pair, and pull it smooth before buckling. Our guide to choosing merino ski socks covers height, cushioning and fit, and the socks collection carries the weights that work in a boot.
Related merino guides
Sources
- REI: what to wear skiing and snowboarding
- REI: how to choose base layers
- Health Canada: extreme cold
Image: Merino Mart catalogue. Browse base layers.