One lightweight merino base layer bottom, and nothing else. Legs are the part of a ski kit people most reliably overdress, because insulated ski pants already provide substantial warmth and moving legs generate a lot of heat. A single base layer bottom in 150 to 190 gsm is right for most conditions.
Why legs need less than you think
Two things are working in your favour below the waist. Ski pants are usually insulated and always wind-resistant, which is more protection than most ski jackets provide on their own. And your legs are doing the work — the large muscles driving a turn produce considerable heat.
| Conditions | Weight | Notes |
|---|---|---|
| Spring skiing | None, or 150 gsm | Insulated pants alone are often enough |
| Typical resort day | 150–190 gsm | The default for most people, most days |
| Cold, below −15°C | 190–250 gsm | Only if you run cold or ski slowly |
| Ski touring | 150 gsm | You will overheat on the climb in anything more |
| Shell pants without insulation | 190–250 gsm | The base layer is doing the insulating here |
Overdressing your legs is also harder to fix than overdressing your torso. You can open a jacket on a chairlift; you cannot remove a base layer bottom without finding a washroom.
Fit matters more than weight
A base layer bottom should be close-fitting from waist to ankle without compressing. Loose fabric bunches behind the knee, which is uncomfortable within a few runs, and gathers at the ankle, which is a genuine problem once a boot is involved.
The waist should sit high enough to overlap your base layer top with no gap at the lower back, and stay there when you bend. A gap at the lower back is where snow goes after a fall.
The boot cuff problem
The single most common mistake is tucking base layer bottoms into ski socks. Fabric inside a ski boot bunches at the ankle, adds volume the boot does not have, and creates pressure points against a rigid shell that has no give at all.
Base layer bottoms should end above the boot cuff, or go over the top of the sock so nothing enters the boot. Many ski-specific bottoms are cut shorter for exactly this reason, finishing at mid-calf. If yours are full length, pull them over the sock rather than under it.
What not to wear
- Cotton anything. Sweat gets absorbed, held against skin, and stays there for the day.
- Jeans. Stiff, cold when damp, and bulky under a shell. This happens more often than it should.
- Two base layers. Compression plus a friction interface between them. One correct weight beats two thin ones on legs.
- Loose track pants or sweatpants. Bulk and bunching, particularly at the knee where a ski pant already has to flex.
- Anything with a thick seam at the knee or inner thigh. These become pressure points across a day of flexing.
Bibs change the equation slightly
Bib ski pants cover the lower torso, which adds warmth over the kidneys and removes the waist gap entirely. With bibs you can often drop a base layer weight compared with regular ski pants, since the bib is already doing part of that job.
They also change how the base layer top and bottom interact. A full-length base layer bottom under a bib can create three overlapping waistbands, which is bulky and uncomfortable across a day. A shorter, ski-specific bottom avoids the stack, and a one-piece base layer avoids it entirely if you do not mind the trip to the washroom.
Women, men and cut differences
Base layer bottoms are one of the garments where the cut genuinely differs rather than being a marketing distinction. Rise height, hip shaping and the position of the waistband all vary, and a poor fit at the waist is what produces the lower-back gap. Inseam length differs too, which matters given how much depends on where the bottom ends relative to the boot cuff.
Try them on with the ski pants you will wear. A bottom that fits well on its own can sit awkwardly once a bib or a high-waisted ski pant is over it, particularly where waistbands stack. Check that you can crouch fully without the waistband pulling down at the back.
Putting the lower half together
The complete system below the waist is a base layer bottom, one pair of ski socks that reaches above the boot cuff, and insulated or shell ski pants. That is genuinely all of it, and adding to it usually makes things worse rather than better.
If you are cold, check whether your core is warm enough before adding to your legs — the body restricts blood flow to extremities to protect core temperature, so a warmer base layer top often does more for cold legs and feet than anything you put on your legs. Our guide to what to wear under a ski jacket covers the upper half.
Related merino guides
Sources
Image: Merino Mart catalogue. Browse base layer bottoms.