A good set of base layers is the baseline (sorry) for most layering systems to keep you warm on any outdoor excursion. The majority of our favorites are made with a high percentage of Merino wool or other natural fibers, which feel soft next to the skin while wicking sweat and providing odor resistance during sweaty outings. We tested a range of base layers, from lightweight sun hoodies to heavier Merino layers for hiking, skiing, and staying warm around a campfire.
Our favorite base layers can all be used for both daily wear and high-intensity activities, and are versatile enough to be worn alone or as part of a layering system. These are our top tested picks for backpacking, hiking, sightseeing, and more.
This is the set we reach for during winter activities and lounging around the house alike as this versatile midweight Merino functions equally well as a cozy camp layer and the top is stylish enough to wear while running errands and attending casual dinners around town. The top and matching bottoms pack down small and don’t take up much room in our bags during travels, and they are so soft we love wearing them around the house and during long travel days.
These are 100 percent Merino wool, which is less common than a Merino/synthetic blend. The fully natural fibers are incredibly soft and wicking, and these are some of the most odor-resistant base layers we’ve tested. The top fits slightly snug, but still has plenty of room for full range of motion, and paired with a puffy jacket and a shell makes for an excellent three-part layering system for a range of winter activities. We did find the pants to be a little long and experienced some bunching around our ankles, but not enough where it became a real fit issue. There is also a men’s version of the top and Merino bottoms.
The Details: XS-4XL women’s, S-XXL men’s | Merino wool | Midweight
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A two-pack of these synthetic tops will run you less than half the cost of other base layers. Free Country keeps the cost of these layers down by using entirely synthetic materials, which means these won’t be as soft or odor-resistant as base layers made with natural fibers, yet they do have a Silvadur anti-odor treatment, which helps keep some of the stink at bay, and the material blend is sleek and breathable.
We’ve worn these on springtime runs in moderate weather, and they wick sweat well while keeping us warmer than just a thin t-shirt. This has an easy-to-layer scoop neck and convenient thumb holes, but we do wish the fabric didn’t look quite so shiny and technical for daily wear around town. With matching bottoms for women as well as a two pack of tops for men and matching bottoms, this is a great set for anyone looking to stock up on reliable base layers.
The Details: Size S-XXL women’s, S-XL men’s | Polyester, acrylic, rayon, and spandex | Lightweight
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This is one of the softest base layers we tested, and it’s also the softest base layer I’ve ever worn. I wear this as a running shirt in moderate temperatures, and it pairs well with a vest on chillier days. Where this shirt for men and women really stands out is daily wear. Made with a soft, drapey tencel and alpaca blend, the silky knit means it fits perfectly loose without feeling sloppy.
The material is lightweight and thin (which means the outline of anything you’re wearing under it might show), but we love how airy it feels to wear all day, and the fact that it isn’t so form-fitting can feel more comfortable when worn on its own. This is also a great travel layer thanks to the natural odor-resistance and ability to wear it multiple days in a row.
The Details: Size XS-XXL women’s, M-XXL men’s | Tencel and alpaca wool | Lightweight
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One of my longtime favorite layers for travel, Free Fly’s breezy Lightweight Hoodie II for men and women is an excellent base layer worn alone or paired with a wind shell when the day gets chilly. Made with 70 percent silky bamboo fibers (and a touch of polyester for durability), this shirt is odor-resistant, quick-drying, and has a UPF 20+ rating so you can wear this for everything from paddle boarding at the lake to hikes above treeline. The hood provides plenty of coverage and can be worn over a hat, and it comes in a range of attractive-but-neutral colors for easy mixing and matching.
We tested this on multiple backpacking trips, including a hot July trip around Jackson Hole and on a thru-hike in Spain in August. We were impressed with everything from the breathability to the softness of the fibers, and felt no discomfort even when worn for long hours under a heavy pack. The fit of this is a bit on the looser side, and we like wearing it over a tank top or t-shirt, providing an extra layer on cooler mornings. Overall, this is a great option for everything from travel to sun protection to a base layer on cold days.
The Details: Size XS-XXL women’s, S-3XL men’s | Bamboo viscose and polyester | Lightweight
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Artilect’s Flatiron 185 Quarter-zip for men and women is a midweight option that combines high-collar draft protection with a generous zipper for dumping heat during high activities. Made almost entirely with lofty, ultra-tough Nuyarn Merino, this base layer is super durable thanks to the Nuyarn, which is essentially a way of processing Merino that wraps the fibers around a tough filament, providing a more lofted feeling and impressive longevity, even with a lower percentage of nylon.
We found this to be sufficiently warm during blustery days in Chicago and New York, and easy to move around in while climbing and hiking thanks to the gusseted underarms. The shirt wicks sweat and breathes well, helping it stay stink-free even during all-day wear. We do feel like Nuyarn is less soft than a standard Merino construction, and some people will prefer to wear something underneath — we found this to be itchy for lounging, but once we got moving were grateful for the durable and warm material.
The Details: Size XS-XL women’s, XS-XXL men’s | Nuyarn Merino and nylon | Midweight
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This is our favorite set for ski season, thanks to the heavier Merino knit and tall neck that can be pulled up like a balaclava. These are both breathable and insulating, making them a great option for resort days riding the lift as well as higher-output activities like cross-country skiing. They have excellent temperature regulation, and the polyester component lends just enough durability that we haven’t noticed any pilling.
The tall neck gaiter is different from other layers we tested, but we were happy to see it didn’t get in the way of external layers, and it’s not too thick and bulky. The matching pants are loose enough we can wear them over another set of leggings, and while this top isn’t the softest layer on our list, it still feels fine to wear with nothing underneath. The men’s version comes with the same tall neck, but with the addition of a hood.
The Details: Size XS-XL women’s, S-XXL men’s | Merino wool and nylon | Midweight
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The fabric is just a bit sheer, so if you wear a darker layer underneath, it will likely show through.
The Ibex Woolies Pro Tech Crew for men and women were one of the softest base layers we tested right out of the box. The fabric is very stretchy and lightweight with a semi-sheer look (so we do recommend wearing nude layers underneath if you’re worried about under-layers showing though). We love how comfortable it is while still being both breathable and also very warm when layered under thicker materials.
Despite the fact that it is made primarily with Merino wool, it’s not itchy at all. We also like how the thumbholes are hidden, so there’s not an obvious hole in the shirt when you’re not using them, which makes it versatile to wear as just a regular everyday long-sleeve shirt, too.
The Details: Size XS-XXL women’s, S-XXL men’s | Merino wool and nylon | Lightweight
Others We Liked
We’ve tested a lot of base layers while hiking, skiing, sightseeing and more. While some we liked for leisurely activities, they had some minor flaws that we just didn’t love.
Smartwool Women’s Intraknit Thermal Merino Base Layer Crew: The nearly seam-free construction and body-mapped design has a sleek fit and doesn’t shift during activities, but we found them to be less versatile than others we tested, and overall we prefer Smartwool’s Quarter-zip style.
Wondery Outdoors Anza Long Sleeve Base Layer: This unique top combines the fit of an athletic base layer with the design of a fashionable top, perfect for wearing under an outer layer or sweater. The fit is compressive, and it comes with a built-in bra top, but the low scoop neckline and back isn’t as comfortable for hiking.
Travel + Leisure
Our Testing Process
We tested a variety of base layers — tops and bottoms — this season on hikes, ski excursions, and camping trips across the country. Before putting the layers on, we examined the stretch, feel, and overall quality of the materials. We then wore each base layer on various hikes and other outdoor excursions from Oregon to New York to determine how they worked for different activities in different environments.
Each layer was worn as a standalone piece and underneath heavier outer layers. After each wear, we washed and dried each layer following manufacturer care instructions. We were careful to reevaluate the base layers each time to determine if the fabric quality had been diminished in any way — from shrinking to fading.
Tips for Buying Base Layers
Prioritize warmth
With the exception of ultralight sun hoodies, most base layers are worn to provide an initial layer of warmth (either on their own or with other clothes). Look for at least 185 grams per square meter (GSM) Merino if you’re seeking a warmer layer, or aim for products that describe themselves as “midweight.” Merino and alpaca wool (the two natural fibers we most recommend) are both naturally temperature-regulating and provide good insulation, so prioritizing layers with a high percentage of those fibers is your best bet.
Look for durability
Base layers can be tricky when it comes to durability. Natural fibers like Merino and alpaca wool have less structural integrity than synthetics like polyester and nylon, and many layers with “Merino” in the name are actually made with a blend of natural and synthetic. This is a good thing, as a percentage of nylon, spandex, or polyester can help with shape retention and prevent holes from developing.
If you do choose a fully natural base layer, make sure to avoid abrasive surfaces, and stitch up any holes as soon as they develop. And always read the care instructions for your base layer — some are best line dried, and I always recommend washing on a cool/gentle cycle.
Consider the three-layer rule
For most of my cool and cold-weather activities, I follow the three-layer rule. That is: base layer, mid-layer, and outer layer. You can mix and match the weights of these layers depending on the conditions and activity output. For example, my ideal winter hiking system is a Merino-blend base layer under a stretchy fleece, with a windproof (or waterproof) shell on top. The base layer is sweat-wicking and keeps your skin dry, the mid layer provides insulation, and the shell ensures no wind cuts through.
Frequently Asked Questions
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What is the best material for a base layer?
The best material for a base layer is a blend of natural and synthetic fibers. Depending on activity and conditions, I am for around 50-70 percent natural (usually Merino) and the rest polyester or nylon. Some base layers have a touch of spandex for shape retention. Layers for cold weather will have more Merino for insulation, while layers with more synthetic tend to be best for warm weather. Tencel, a soft fiber made from bamboo, is great for ultralight summer base layers.
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What is the difference between base layer and thermals?
Base layers and thermals are often used interchangeably, but I consider base layers to be more versatile, used both during activities and while camping or sleeping outdoors. Thermals are geared more toward insulation (think classic waffle-patterned pajamas) and are great for camping and sleeping, but not necessarily wearing on their own. They usually don’t wick sweat and breathe as well as base layers, but always check the material blend regardless.
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Should base layers be tight or loose?
Base layers are usually tight. Since we wear them underneath outer layers, they have to be sized to fit comfortably under a shell, mid-layer, and/or pants. However, you don’t want your base layers to fit so tight that they feel binding and restrict range of motion. The best fit is one that hugs your body but is made with articulation and gusseted body-mapping.
Why Trust Travel + Leisure
Maggie Slepian is a Montana-based writer, editor, and outdoor lover. She is an avid backpacker, bikepacker, and four-season outdoorsperson, and tests dozens of base layers each season, from trail running to skiing. For this piece, she combined her own testing experience with feedback and tested items from T+L editors.
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