Our editors independently research, test, and recommend the best products and services; you can learn more about our review process here. We may receive commissions on purchases made from our chosen links.
Best Overall: SmartWool Merino 250 at Amazon "This top is all but guaranteed to become your favorite go-to."
Best Budget: Duofold Mid-weight Wicking Thermal Pant at Amazon "Two layers of fleecy cotton fabric are blended together for a sleek silhouette that fits close to the body."
Best for Men: DRSKIN Thermal Wintergear Pants at Amazon "They’re best for activities like skiing and snowboarding, rather than hardcore winter mountaineering."
Best for Women: Odlo Women’s BlackComb Evolution Warm Crewneck Top at Amazon "No matter how many times you put it through the washer, this top keeps its shape."
Best for Running: Patagonia Capilene Midweight Crew at REI "This version sees repositioned shoulder seams, which Patagonia says will help reduce chafing."
Best for Skiing: Helly Hansen Lifa/Dry Stripe Base Layer Crew at Amazon "It’s great for heading out on the trail, too — with a weight of just 5.5 ounces, it packs up easily."
Best for Hunting: Arc'teryx Rho AR at Amazon "The zip-neck is also great for when you need just a bit of air to cool things down."
Best for Kids: REI Co-op Merino Midweight Half-Zip Base Layer at REI "The wool is soft, not scratchy, thanks to 18.5-gauge, ultrafine merino."
Our Top Picks
Best Overall: SmartWool Merino 250
With a slim fit that hugs the body and odor-resistant material, SmartWool’s base layers are great for men and women hitting the slopes or going for a run on a cold winter morning. They easily wick away moisture, and thanks to the nonsynthetic construction, don’t give you the clammy chills when you break a sweat. Another plus? The flatlock seams, which keep the close-fitting tops from chafing skin. This top, while on the pricey side, is all but guaranteed to become your favorite go-to. Like all merino wool products, these require a little more effort to care for (hint: wash them in a lingerie bag), but it’s worth it for these lifesavers. (There's also a men’s version and it also comes in a lighter version for weather that’s not too extreme, though they do run warmer than you might expect—especially if you run hot yourself.)
Best Budget: Duofold Mid-weight Wicking Thermal Pant
A favorite among those who don’t need a base layer often enough to justify a high price tag — or who need thermal pants less often than they need to wear a thermal top — Duofold’s Mid-weight Wicking Thermal Pants are the perfect choice. Two layers of fleecy cotton fabric are blended together for a sleek silhouette that fits close to the body to keep wearers warm, rounded off by flat seams that don’t chafe, a front fly and high-quality fabric that won’t fall apart anytime soon. Cuffed ankles make these super-easy to tuck under boots, too. Duofold’s proprietary C Vapor technology wicks away moisture well, leaving skin dry even when it’s working up a sweat. While these might not see you to the summit of a mountain, warmth-wise — nor are they good for high-activity winter activities — they’re great for chilly hikes, camping and everyday use under jeans during the depths of winter. ( Shop for the women's version.)
Best for Men: DRSKIN Thermal Wintergear Pants
These leggings are exactly what you want on a cold winter day, whether you’re heading out on a run or hitting the slopes. Lined with thin-but-effective thermal microfleece, they’re great for those who are allergic to wool — but cozy for all. (Don’t be alarmed by how thin the microfleece is — it’s far less bulky than regular fleece but holds up just as well.) The compression fit is great when it comes to being active in the cold weather, while the TWC-Way Air Circulation means that they keep you warm in the winter and, yes, surprisingly cool in the summer. They’re best for activities like skiing and snowboarding, rather than hardcore winter mountaineering, but for these low- to medium-exertion activities, the great moisture-wicking talent of these pants is a winner, and once washed, they dry quickly for your next adventure. Just keep in mind, these tend to run a little small and short in size, so plan ahead and measure up if you’re on the cusp.
Best for Women: Odlo Women’s BlackComb Evolution Warm Crewneck Top
A tight fit and stretch fabric (made partially from recycled materials) gives you a huge range of motion, whether you’re skiing, running or just shoveling the driveway in the snow. Besides being incredibly stylish, these separates are warm without risk of overheating, thanks to their breathability Another built-in bonus? The seamless knit technology that prevents unpleasant issues from chafing seams. No matter how many times you put it through the washer, this top keeps its shape, to the point where it almost feels like it’s sculpting itself around your limbs and muscles. Odlo’s proprietary Effect technology also prevents smells from seeping into the fibers, which is great for periods of extended use or just multiple washes over winter weeks.
Best for Running: Patagonia Capilene Midweight Crew
Yes, it’s on the pricey side, but when it comes to an activity you do almost every day, this form-fitting, crew-neck base layer will keep you warm — while holding up when it comes to durability. Double-knit Polartec Power Grid fabric, made of mostly recycled polyester, wicks away sweat incredibly well and keeps the shirt super-breathable, while polygiene permanent odor control keeps the fabric from permanently absorbing odors. This version sees repositioned shoulder seams, which Patagonia says will help reduce chafing. Thumb loops are great for stopping the sleeves from riding up, and you’ll want to use them as the sleeves run a bit short (conversely, if you’re in the can’t-stand-thumb-loops camp, you might want to skip this shirt). It’s not great in really cold temps, but for spring, fall, and the tail ends of winter, this does the job. The Fair Trade-certified top also comes in women’s and a zip-neck version, if crewneck isn’t your thing.
Best for Skiing: Helly Hansen Lifa/Dry Stripe Base Layer Crew
Breathability is the best part about this incredibly lightweight thermal top (also available for women), which uses the company’s proprietary stay-dry technology to get moisture off the skin, into the fabric and then quickly evaporates it, basically before you even notice it’s there. It’s not the warmest option available — say, for heading out to grab the mail on a cold morning — but you won’t want the warmest option if you’re doing a mid- to high-energy activity where you’re working up a sweat. (That being said, the high collar is wonderful at keeping chilly breezes out.) It’s great for heading out on the trail, too — with a weight of just 5.5 ounces (for a size medium), it’s easily packable and portable for backpackers. One hint: If it’s not tucked in — which it usually will be, if you’re wearing ski or snowboarding gear — it can ride up sometimes, though tight sleeves keep it from doing so when you’re reaching up for that ski-lift bar.
Best for Hunting: Arc'teryx Rho AR
When it comes to low activity in the cold, you don’t need — or want — the same kind of base layer as you would for more high-activity, wintry pursuits. Plus, you have enough to worry about with gear that wearing anything bulky just isn’t going to be great. With the Arc’teryx Rho AR, its synthetic Polartec power stretch fabric is thin but incredibly warm, and flatlock seams mean there won’t be any chafing. The zip-neck is also great for when you need just a bit of air to cool things down; meanwhile, the body-hugging fit will keep you toasty. It’s also highly layerable, making this a great first (or second) layer on long, cold days. As high as the price tag is, it’s the super-comfortable top it should be, with material that’s soft against the skin. That being said, with high-activity, moisture can sometimes sit on your skin in this top before being wicked away, so you’ll want something else for skiing or running.
Best for Kids: REI Co-op Merino Midweight Half-Zip Base Layer
Warm, dry kids are happy kids — and the last thing you want on a family adventure is for the little ones to be uncomfortable or wet. Having something warm, but that wicks away sweat, is critical. Parents love REI’s midweight base layers for their little ones — the zip neck (with a convenient chin guard) is great for when kids need to cool down just a tad, too. The wool is soft, not scratchy, thanks to 18.5-gauge, ultrafine merino, and the flat seams on this top prevent chafing from ever being a problem. The perfectly designed drop-tail hem keeps this shirt tucked in, and for bigger kids, it protects lower backs under a pack’s belt. Keep in mind, however, that you’ll also want to consider that this isn’t something to buy thinking kids will grow into them: a tighter fit is critical to base layers, otherwise, the heat they’re meant to trap will just leak out.