Activities The Great Outdoors What to Wear Under Ski Pants Share PINTEREST Email Print Adam Clark / Aurora Photos / Getty Images The Great Outdoors Skiing Gear Basics Hiking Climbing Snowboarding Surfing Paddling Fishing Sailing Scuba Diving & Snorkeling Learn More By Mike Doyle Mike Doyle is an award-winning skiing journalist who grew up in New York snow country and has skied all over the world. our editorial process Mike Doyle Updated October 01, 2018 What you wear under your ski pants is called a base layer. You can also call it long underwear or even long johns, but don't think you should wear old-fashioned cotton long underwear. Today's base layers are made with synthetic or fine natural fabrics that help you stay dry, which in turn helps you stay warm. Cotton does a poor job of both. You'll also find that base layers come in different weights and, for the pants, different lengths. Base Layer Basics The base layer typically is the only layer worn under ski pants. As for the upper body, you might also wear a mid layer over a base layer, as well as a ski jacket. A single base layer works well for most conditions, but for very cold weather, you might want a second base layer under your ski pants, or switch to a single heavyweight base layer. A base layer should be snug-fitting and relatively thin, allowing for full movement inside your ski pants without bunching or adding bulk. It should be comfortable enough that you forget you're wearing it. Super-tight or compression pants usually aren't that comfortable. Base Layer Fabrics There are a number of alternatives to the classic cotton long johns or leggings, which hold moisture against your body. Synthetic materials are dominating the clothing market and are offering affordable, non-restricting, moisture-wicking, breathable layers to wear under ski pants. When you wear a base layer that keeps moisture away from your skin, you are less likely to have dramatic changes in body temperature, which is a huge advantage in cold conditions. While cotton and even treated silk may be getting overshadowed by these new synthetic materials, wool is still holding its own in the clothing market. Like the synthetic materials, wool has great wicking properties but it doesn't dry as fast as the synthetics do. However, you can't beat wool's ability to hold in the heat, so this natural fabric may be the best choice on those extra-cold days. Many natural-fiber base layers are made with merino wool, or a combination of merino wool and synthetic fibers. These are great performers but can be pricey. Base Layer Weight Base layers generally fall into three different weight categories: Lightweight: Standard long-underwear weight is usually the best choice for ordinary winter weather and ski activity. It is thin enough to wear under a second base layer or mid layer, if desired. It's also primarily used for wicking moisture from the skin and serving as a "second skin" for warmth. Midweight: Is worn alone as a heavier base layer or as an insulating layer over a lightweight base. Heavyweight: Is sometimes called thermal weight or expedition, a thick secondary base layer, typically worn over a lightweight base for extreme cold. This should be looser-fitting than a lightweight or midweight layer but should not be bulky or restrictive. Pant Length Base layer pants come in two lengths: full and 3/4. Full-length pants are the standard length that go down to the ankles. Shorter, 3/4-length pants are specifically designed for skiers and snowboarders. They stop at the top of your ski boots so you don't have an extra layer or a pants cuff inside your boots.