As your next-to-skin article of clothing, a baselayer plays a fundamental role in pulling moisture away from the body and regulating core temperature. It’s far easier to justify purchasing a nice down jacket, but a baselayer can be just as important for activities like skiing, hiking, and climbing. To start, avoid cotton (like the old adage “cotton kills”). You’ll need a fabric that won’t stay wet, and merino wool and polyester are the most common choices. Merino is ultra soft, warm, and handles moisture well, but is very expensive. Polyester blends are cheaper and more durable but aren’t as comfortable or resistant to odor. Below are our picks for the best baselayers of 2020. For more information, see our baselayer comparison table and buying advice below the picks.

Best Overall Baselayer

1. Smartwool Merino 250 1/4-Zip ($105)

Smartwool Merino 250 baselayerMaterial: 100% merino wool
Category: Midweight
Weight: 10 oz.
What we like: Extremely comfortable and functional.
What we don’t: Pure merino baselayers can have durability issues.

The Merino 250 ¼ Zip from Smartwool is the whole package in a baselayer: it’s super soft against the skin, offers the right amount of warmth, wicks moisture, and repel odors as well as any pair of long underwear can. It’s a great thermal option for skiing and even has a UPF 50+ rating for use as an outer layer during activities like hiking, biking, and running. We prefer the Zip Top version over the Crew, which allows for more ventilation when you’re working up a sweat.

The biggest issues with the Merino 250 are price and durability. If you add Smartwool merino bottoms, you’re looking at around $200 for your baselayers alone. And given that it’s made from 100 percent merino wool, it simply won’t last forever (proper care can help, but from our experience, merino almost always deteriorates after extensive use). If you’re looking for inexpensive thermals that will last for many seasons to come, grab a synthetic like the Patagonia Capilene below. But for the ultimate in comfort and performance, the Merino 250 from Smartwool is our top pick.
See the Men's Smartwool Merino 250  See the Women's Smartwool Merino 250


Best Synthetic Baselayer

2. Patagonia Capilene Midweight Crew ($59)

Patagonia Capilene Midweight Crew men's baselayerMaterial: 100% recycled polyester
Category: Light/midweight
Weight: 6.2 oz.
What we like: Cheaper and more durable than merino wool.
What we don’t: Not quite as soft.

Choosing synthetics over merino wool has clear upsides, the most notable being cost and durability. For just over half the price of the Smartwool above, the polyester Capilene Midweight by Patagonia offers similar warmth and moisture-wicking capabilities. And it likely will last for many seasons—we have Capilene tops that are multiple years old and counting despite heavy use. Plus, it doesn’t hurt that Patagonia has upgraded the latest Capilene Midweight with 100-percent-recycled materials.

What do you sacrifice by going with a synthetic baselayer? Polyester is decently comfortable but not as soft against the skin, and it doesn’t regulate body temperature or repel odor quite as well as wool. This doesn’t mean that your Capilene will get stinky super quickly—and Patagonia has made strides in this area with an anti-odor HeiQ Fresh treatment—but you will find yourself putting it through the wash more often. However, not everyone wants to spend $100 or more on a baselayer, which is why we love Patagonia’s Capilene line. For less or more warmth, try the Capilene Lightweight and Thermal Weight versions.
See the Men's Patagonia Capilene  See the Women's Patagonia Capilene


Best Budget Baselayer

3. Helly Hansen Lifa Stripe Crew ($40)

Helly Hansen Lifa Stripe CrewMaterial: 100% polypropylene
Category: Lightweight
Weight: 5.1 oz.
What we like: Wicks moisture well and a great value.
What we don’t: Not as warm as other baselayers on this list.

There’s a lot to like about this lightweight active baselayer from Helly Hansen. At just $40, it’s one of the cheapest options on this list yet still will keep you dry and decently warm in most conditions. The headliner is the Lifa fabric, which is made from Polypropylene and specializes in wicking moisture away from the skin (it does so much better than polyester). Along with a nice athletic fit, the Lifa Stripe is great for active skiers and other high-output activities like climbing and hiking.

The downside of Polypro compared to polyester or nylon is that it isn’t as warm. The Lifa Stripe Crew falls into our lightweight category, meaning that it provides some insulation but requires a good midlayer or insulated shell in cold conditions. It’s worth the tradeoff for many people who love the performance and value of this baselayer. And it doesn’t hurt that Helly Hansen made the look a little less boring than other options on the list, with some fun colors to choose from and a signature stripe design down the sleeve.
See the Men's Helly Hansen Lifa Stripe  See the Women's Helly Hansen Lifa Stripe


Best Lightweight Baselayer for Warm Weather

4. Smartwool Merino 150 Crew ($85)

Smartwool Merino 150 Crew baselayerMaterials: 87% merino wool, 13% nylon
Category: Lightweight
Weight: 6 oz.
What we like: A great option for cool days and summer nights. 
What we don’t: Thin materials require more care. 

We’ve already listed the Smartwool Merino 250 as our top pick, but we’d be remiss not to include another stellar baselayer in the 150 Crew. The build quality is similar: Smartwool adds 13 percent nylon to the mix for a boost in durability, the weight goes down significantly to 6 ounces (the lack of the zipper matters here too), and you get the same minimalist seams for comfort. Compared to the warm 250 above, the 150 is lighter in weight and ideal for uses like spring skiing, shoulder season hiking, and cool summer nights. You’ll feel like you are wearing much less baselayer, but the boost in coziness and moisture-wicking capabilities are still there. 

It’s worth noting that Smartwool also offers its techy Intraknit Merino 200, which splits the difference between the 150 here and the 250 above. This performance piece is nearly half polyester/elastane (it’s 53-percent merino), incorporates low-prolife seams, and has body mapping with mesh panels throughout for improved ventilation. We haven’t yet had the chance to give the Intraknit baselayer an extended test, but it’s an intriguing option for high-output activities in cold weather when you want a layer that’s both warm and exceptionally breathable. But for mild summer temperatures, the Merino 150 is $35 less and likely all the insulation you’ll need.
See the Men's Smartwool Merino 150 Crew  See the Women's Smartwool Merino 150 Crew


Best Heavyweight Baselayer for the Cold

5. Woolx Glacier LS Heavyweight Crew ($120)

Woolx Glacier LS Heavyweight CrewMaterial: 100% merino wool
Category: Heavyweight
Weight: 17.6 oz.
What we like: Very warm and soft. A great value for an all-merino baselayer.
What we don’t: Because of the thickness and cut, it’s not ideal for high-output activities.

Woolx is a small New York-based company that doesn’t get the hype of a Smartwool or Icebreaker, but the thick Glacier LS is our favorite heavyweight baselayer. Made with 100 percent merino wool, this piece is much warmer and more substantial than the midweight and lightweight options on the list. And because it’s merino, it’s still soft against the skin and breathes well. We’ve used the Glacier LS for everything from skiing and snowshoeing to casual use and have come away very impressed.

To put things in perspective, in terms of thickness the Glacier LS is 400g/m², while the Smartwool Merino above is 250g/m². Both are 100 percent merino and both fall around the $100 price point (the Smartwool gets a $15 edge here at $105). This means that you’re getting much more baselayer for your money from Woolx compared to just about any other merino brand. One consideration is that the Glacier LS does not have a tailored fit like some other baselayers, so it’s more about warmth than anything else. We highly recommend it for downhill skiing in cold places, winter walking, and everyday wear. 
See the Woolx Glacier Heavyweight  See the Women's Woolx Riley Heavyweight


Best of the Rest

6. REI Co-op Merino Midweight Half-Zip ($90)

REI Co-op Merino Midweight baselayerMaterial: 100% merino wool
Category: Midweight
Weight: 8.5 oz.
What we like: A soft, stretchy, and well-made baselayer. 
What we don’t: Pricey for an REI product. 

Of all of REI Co-op’s in-house products, their merino baselayer is one of our favorites. It’s right on the same playing field as heavy hitters like Smartwool and Icebreaker, which is quite a feat given that those companies specialize in wool layering pieces. The REI midweight Half-Zip is soft, warm, has a good amount of stretch, and wicks moisture as well as any. And most importantly, it has handled everything from backpacking to cross-country skiing with ease.

Unlike many REI products, the Merino Midweight Half-Zip doesn’t come at much of a discount, which is why we have it ranked here. The $90 price tag and 200g/m² thickness are the same as Icebreaker's popular Oasis Crewe, although you do get a front zip and higher collar on the REI. And for just $15 more, you can get the legendary Smartwool 250 above, our top pick, which is slightly thicker and warmer at 250g/m². We really like the REI and have had nothing but positive experiences with it thus far, but we’re not ready to dethrone the Smartwool just yet.
See the Men's REI Merino Midweight  See the Women's REI Merino Midweight


7. Kari Traa Rose Half-Zip ($110)

Kari Traa Rose Half-Zip baselayer topMaterials: 100% merino wool
Category: Midweight
What we like: Style meets performance for women. 
What we don’t: Pure merino has a tendency to form holes.

Norwegian-brand Kari Traa balks the shrink-it-and-pink-it trend with a lineup of high-performance outerwear designed from the ground up “for girls, by girls.” You won’t find boxy or bland baselayers here—Kari Traa (the Olympic freestyle skier who founded her namesake company) places a high priority on fun color schemes and well-fitting garments. In short, this is the intersection of technical performance and feminine styling that the market has long needed. And the Rose Half-Zip is one of Kari Traa’s most popular items, featuring a form-fitting design, ventilating front zip with chin guard, high-quality cuffs, and flat seams. In addition, you get a vibrant snowflake pattern with contrasting underarm panels and your choice between a wide variety of colors (nine on Kari Traa’s website at the time of publishing). 

Like the Smartwool 250 and REI Co-op Midweight above, the Kari Traa Rose is made with 100-percent merino wool. On one hand, this means excellent temperature regulation, odor control, and next-to-skin comfort, but on the other hand, it does pose some durability concerns. Because of pure wool’s tendency to form holes, we recommend always layering the Rose Half-Zip underneath a midlayer or shell during activity, and be sure to line dry it after washing (Kari Traa also offers a number of synthetic tops, including the polyester/elastane Fryd). Finally, if the Rose Half-Zip has caught your eye, it’s worth noting that it is also available in hooded and Henley tops and matching bottoms.
See the Women's Kari Traa Rose Half-Zip


8. Patagonia Capilene Air Hoody ($149)

Patagonia Capilene Air hoody baselayerMaterials: 51% merino, 49% polyester
Category: Midweight
Weight: 6.9 oz.
What we like: Amazing warmth in a tiny package; responsibly sourced wool.
What we don’t: Expensive; lacks durability.

Patagonia’s Capilene collection runs the gamut from thermal-weight baselayers to lightweight t-shirts and long-sleeve layers for hiking, and the midweight Capilene Air Hoody stands out as one of our favorites in the lineup. Known for leading the charge in their dedication to sustainable environmental practices, Patagonia outfitted the Capilene Air with recycled polyester (49 percent), and the net result is a responsibly made and truly innovative piece. With a balaclava-style hood, seamless construction, and a heat-trapping merino/polyester blend, the Capilene Air provides a massive amount of warmth in a relatively thin and lightweight package.

Although in theory the polyester make-up of the Capilene Air gives it a bump in durability, we developed multiple holes and runs on our hoody in a matter of weeks. Furthermore, it is noticeably permeable to wind, and the fabric tends to pill and act as catch-all for hair, fuzz, and more. For all these reasons, the Capilene Air makes a poor outer layer, unlike a baselayer like the NW Alpine Alpine Hoody below. But with great odor resistance, impressive wicking and drying properties, and one of the warmest, coziest hoods we know of, it makes a fantastic next-to-skin piece.
See the Men's Patagonia Capilene Air  See the Women's Patagonia Capilene Air


9. Arc’teryx Rho LT Zip-Neck ($125)

Arc'teryx Rho LT quarter zip baselayerMaterials: 84% polyester, 16% elastane 
Category: Light/midweight
Weight: 7.6 oz.
What we like: Soft and cozy for a polyester baselayer and features a zip pocket.
What we don’t: Expensive and not versatile as an outer layer.

Arc’teryx places a premium on high performance, which shows in their baselayer collection. Their Rho series is designed to keep you warm in a variety of winter and shoulder season activities and includes the expedition-weight AR (“all-round”) model, a LT (“lightweight”) hoody, and the zip-neck LT here. Combining polyester with a generous dose of elastane, the zip-neck LT falls between our light and midweight categories, making it an ideal layering piece under a midlayer or shell during low-output activities. We generally prefer merino baselayers for their better next-to-skin feel, but the Rho LT stands out with a soft brushed interior, and it doesn’t hurt that its synthetic build is much more durable than wool.

Arc’teryx paid attention to a number of small details with the Rho LT. Gusseted underarms and a slight drop hem increase mobility, and a laminated zipper pocket on the chest for men (arm for women) are great for storing small items like chapstick or a credit card. $125 is a high price to pay for a non-merino baselayer (most synthetic options here are about half the cost), and the Rho LT’s trim, technical fit means it doesn’t function well as a standalone piece. That said, it’s hard to go wrong with Arc’teryx’s quality—the Rho is built to last. And if you have a tendency to run cold or want a winter-ready baselayer, the fleece-lined Rho AR offers a heavy dose of insulation and cozy loft at an impressively low weight—almost a half-pound less than the all-merino Woolx above. 
See the Men's Arc'teryx Rho LT  See the Women's Arc'teryx Rho LT


10. NW Alpine Spider Hoody ($129)

NW Alpine Spider Hoody baselayer topMaterials: 92% polyester, 8% spandex
Category: Midweight
Weight: 11 oz.
What we like: Durable enough to be worn as an outer layer.
What we don’t: Expensive for polyester.

NW Alpine certainly isn’t a household name, but this small Portland, Oregon, company designs and constructs alpine climbing apparel on par with the best. Although they only make a handful of items, each of their products is a study in quality over quantity. And their Spider Hoody is one of our favorite baselayers: it’s comfortable, warm and breathable, and has unmatched durability. In fact, we’ve put ours through six years of climbing abuse—much of the time without a jacket over top—and it has yet to develop any holes or tears. 

All that said, the Spider Hoody won’t earn you too many style points: it lacks the odor resistance of merino and is available in only a few simple colors. Furthermore, $129 is a hefty price tag for a polyester baselayer, and it can often be hard to find in stock online or in stores. However, the most impressive durability of any baselayer we’ve worn—combined with features like an under-the-helmet hood and chest zip—set the Spider Hoody apart as a highly functional and long-lasting performance piece. 
See the Men's NW Alpine Spider  See the Women's NW Alpine Spider


11. Black Diamond Solution 150 Merino Crew ($120)

Black Diamond Solution 150 Merino Crew baselayerMaterials: 78% merino, 22% polyester
Category: Lightweight
Weight: 6.7 oz.
What we like: The benefits of merino, plus moisture wicking and durability.
What we don’t: Expensive for a lightweight baselayer.

Black Diamond’s new Solution Wool lineup is making waves, namely for its innovative NuYarn technology. Many manufacturers weave fibers together with merino to reap the benefits of both, but NuYarn takes it to the next level, wrapping nylon with extra-fine merino fibers for a thread that exudes technical performance down to its literal core (similar in concept to Arc’teryx’s Satoro AR). And the result is impressive: compared to a baselayer like the Smartwool Merino 150 above, the Solution 150 is noticeably more durable and dries out very quickly when wet (great news for those who are prone to working up a sweat). 

After wearing the Solution 150 for six days straight while hiking in Patagonia, we were impressed with how well it held its shape and resisted odor. Under a loaded backpack, the offset shoulder stitching was comfortable and mitigated pressure points, and the thumb loops are sleek and well-constructed. In fact, our biggest gripe with the Solution 150 is its price—at $119, it’s $34 more than Smartwool’s comparable baselayer top, which is why we rank the BD here. But cost aside, the Solution 150 has solid all-around performance, and will last longer than most merino baselayers.
See the Men's BD Solution 150 Merino  See the Women's BD Solution 150 Merino


12. Craft Active Extreme Crewneck 2.0 ($80)

Craft Active Extreme 2.0 baselayerMaterials: 100% polyester (body); 4% elastane (side panels)
Category: Lightweight
Weight: 4.4 oz.
What we like: Absolutely fantastic all-around performance.
What we don’t: Technical design and fit isn’t for everyone.

Craft is a Swedish gear company with a cult-like following that is known for technical baselayers. In particular, they specialize in aerobic activities like cross-country skiing, biking, and running. The fit and styling clearly have performance in mind, and Craft may be overkill for casual use, but they make go-to baselayers for a lot of serious athletes.

The Active Extreme 2.0 isn’t your average thermal: it’s noticeably thin and lightweight and has a technical fit that is among the best on the list for those who really like to move (some baselayers have an athletic fit, but Craft really takes it to another level). As a result, this is decidedly not a casual layer. With high amounts of breathability (aided by ventilating mesh in high-sweat zones) and impressive warmth when you need it, Craft’s Active Extreme is ideal for high-output days.
See the Men's Craft Active Extreme 2.0  See the Women's Craft Active Extreme 2.0


13. REI Co-op Lightweight Base Layer Crew ($40)

REI Co-op Lightweight men's Base Layer CrewMaterials: 92% polyester, 8% spandex
Category: Lightweight
Weight: 6.5 oz.
What we like: Simple yet functional.
What we don’t: Not super comfortable or a high performer.

In terms of bang for your buck, it’s hard to top REI baselayers. For $40, the Lightweight Crew offers most of the performance of the more expensive options above in a simple yet functional design. Additionally, REI honed things in even further with 8 percent spandex in the construction, which gives it a nice, stretchy feel. Paired with the matching bottoms, you can pick up a full long underwear set for $80 ($25 cheaper than just a merino top from Smartwool).

What are the downsides of the REI? We’ve found the lightweight model works well for mild resort skiing days, hiking, and casual use, but you may not be warm enough in frigid temperatures. And although the fabric is comfortably silky, it can’t compete with merino or even Patagonia’s Capilene in terms of softness and comfort (and it’s even more prone to holding in body odor). These issues aside, the REI Lightweight Crew is a good way to kit yourself out this winter on a budget.
See the Men's REI Lightweight Crew  See the Women's REI Lightweight Crew


14. Icebreaker Oasis Crewe ($95)

Icebreaker Oasis Crewe men's baselayerMaterial: 100% merino wool
Category: Midweight
Weight: 8.9 oz.
What we like: Softer against the skin than Smartwool.
What we don’t: Slim fit and dense weave lags behind in breathability.

The Oasis Crewe from Icebreaker is as versatile as any baselayer on this list. It’s made from 100 percent merino wool, is super soft, and has a performance fit that works well for skiing and cool-weather hiking. And because of the clean styling and plethora of colorways and designs, you easily can wear it as a standalone piece.

If you’re considering the Oasis, it’s a head-to-head matchup with the Smartwool Merino 250 above. Both models are made from 100 percent merino and the prices are similar (the zip-neck version of the Oasis is $100). Both are comfortable, wick moisture well, and don’t trap odor like synthetics. But we give the slight edge to the Smartwool because the dense weave of the Icebreaker’s fabric doesn’t release hot air quite as efficiently. Despite having a lighter fabric weight (200 vs. 250g/m²), it can start to feel muggy when you’re working up a sweat. On the other hand, we do give it the edge in next-to-skin softness.
See the Men's Icebreaker Oasis  See the Women's Icebreaker Oasis


15. Ortovox 185 Rock’N’Wool Long Sleeve ($110)

Ortovox 185 Rock'N'Wool Long-Sleeve baselayerMaterial: 100% merino wool
Category: Light/midweight
Weight: 6.9 oz.
What we like: Great styling and super-soft hand feel.
What we don’t: Expensive and lacks durability.

We’ll start with the basics: the Ortovox 185 Merino long-sleeve crew is a standard merino baselayer. Much like the chart-topping Smartwool, it’s made with 100-percent wool, which means you get uncompromised odor resistance, great temperature regulation, and a cozy, soft touch. At 185 grams per square meter, it’s lighter than the Smartwool 250, meaning it’s more suitable for shoulder-season or high-output activities. That said, the thin fabric, paired with the fact that it’s not blended with a synthetic material, does make us concerned about the Ortovox’s durability (even Smartwool’s 150-weight shirt features a merino/nylon blend).

But here is where the Rock’N’Wool stands out: first, the Ortovox Wool Promise ensures that their product comes from ethical and certified sheep farms. And second, we just can’t get enough of the styling on the Rock’N’Wool—if you want a merino baselayer with some flair, the multi-colored designs really stand out in the conservative and largely bland baselayer market. For a versatile, breathable next-to-skin layer that can take you straight from skin track to après, the Ortovox 185 is an eye-catching choice.
See the Men's Ortovox 185 Rock'N'Wool  See the Women's Ortovox 185 Rock'N'Wool


16. Norrøna Wool One-Piece ($199)

Norrona Wool One-Piece baselayerMaterials: 89% merino, 11% nylon
Category: Midweight
Weight: 14.1 oz.
What we like: Maximum protection from the cold.
What we don’t: One-piece design is limited.

For maximum protection against the cold, a one-piece baselayer is hard to beat. Norway-based Norrøna’s offering in this category covers you from your head to just about your ankles with incredibly warm, comfortable, and breathable merino wool. The addition of polyamide (nylon) adds durability while also helping to wick moisture. Further, a long front zipper and drop bottom mean you can wear the One-Piece all day long. 

The Wool One-Piece may be fun and useful for certain hardcore cold-weather adventurers, but it pretty clearly has limited appeal. The price tag is steep for a baselayer and most of the features are targeted to a very specific audience (including mountaineers, ice climbers, and the occasional backcountry skier). But we won’t fault you for being tempted by the idea of a functional and cozy adult onesie—and it’s hard to argue with the protection and warmth at a pretty darn light 14.1-ounce weight.
See the Men's Norrøna Wool One-Piece  See the Women's Norrøna Wool One-Piece


17. Mountain Hardwear Ghee Hoody ($80)

Mountain Hardwear Ghee Hoody baselayerMaterials: 85% polyester, 15% elastane
Category: Lightweight
Weight: 7.9 oz.
What we like: Great breathability and a trim, stretchy fit.
What we don’t: More expensive than the Patagonia Capilene Midweight and REI Lightweight above.

Mountain Hardwear used to make a baselayer called the Butterman, and the Ghee (see what they did there?) is an equally soft and supple piece. Featuring lightweight polyester with built-in elastane and a breathable panel across the upper back and underarms, this layer is built to keep air moving and moisture wicking during high-output activities. The trim and stretchy fit is great for mobility while skiing or climbing (no excess fabric getting in the way), and features like thumb loops and a generous yet low-profile hood add great performance chops. Added up, the Ghee Hoody is a good-looking baselayer designed for active use.

With the polyester Ghee, you don’t get the odor resistance and temperature regulation of a merino layer, but the lightweight and airy design goes a long way in keeping things feeling fresh while still insulating against a chill. And while you can find cheaper polyester tops like the Patagonia Capilene Midweight and REI Co-op Lightweight above, the Ghee is priced fairly competitively at $80 for the hooded version, especially compared to the NW Spider Alpine Hoody above (although keep in mind the Spider is warmer and more durable). And mountain Hardwear offers this same design in both crew and quarter-zip long-sleeve shirts and tights, which feature the same airy panel on the lower back, between the legs and behind the knees.
See the MTN Hardwear Ghee Hoody  See the Women's MTN Hardwear Ghee Hoody


18. L.L. Bean Silk Underwear Crewneck ($50)

L.L. Bean Silk Underwear Crewneck baselayerMaterial: 100% silk fabric
Category: Lightweight
What we like: Cozy and great for layering.
What we don’t: Lacks the performance of merino or polyester.

Silk can’t compete with merino or polyester in terms of warmth, moisture wicking, and durability, but it’s not without its place in the baselayer world. Those who prize comfort above all else might choose silk for sleeping, around camp, and other low-output activities. Furthermore, silk is so thin that it can easily be worn underneath slim-fitting layers without creating extra bulk. And for only $50, L.L. Bean’s Silk Underwear is well-made and more durable than most silk options.

We don’t recommend wearing the Silk Underwear Crewneck for any sort of high-output activity—it simply does not breathe as well as merino or polyester. Moreover, if you want it to last, the shirt should always be layered with a mid or outer shell. In the end, silk falls short of the wool and polyester options above in nearly every performance category. But if you prioritize comfort above all else and like the feel of silk, the L.L. Bean Crewneck is worth a look.
See the Men's L.L. Bean Silk Crewneck  See the Women's L.L. Bean Silk Crewneck


Baselayer Comparison Table

Baselayer Price Materials Category Weight g/m²
Smartwool Merino 250 1/4-Zip $105 100% merino wool Midweight 10 oz. 250g/m²
Patagonia Capilene Midweight $59 100% recycled polyester Light/mid 6.2 oz. 147g/m²
Helly Hansen Lifa Stripe Crew $40 100% polypropylene Lightweight 5.1 oz. 125g/m²
Smartwool Merino 150 Crew $85 87% merino wool, 13% nylon Lightweight 6 oz. 150g/m²
Woolx Glacier LS Heavyweight $120 100% merino wool Heavyweight 17.6 oz. 400g/m²
REI Merino Midweight Half-Zip $90 100% merino wool Midweight 8.5 oz. 200g/m²
Kari Traa Rose Half-Zip $110 100% merino wool Midweight Unavail. Unavail.
Patagonia Capilene Air Hoody $149 51% merino, 49% polyester Midweight 6.9 oz. 190g/m²
Arc’teryx Rho LT Zip-Neck $125 84% polyester, 16% elastane Light/mid 7.6 oz. 190g/m²
NW Alpine Spider Hoody $129 92% polyester, 8% spandex Midweight 11 oz. 194g/m²
Black Diamond Solution 150 $120 78% merino, 22% polyester Lightweight 6.7 oz. 150g/m²
Craft Active Extreme Crewneck $80 100% polyester (body); 4% elastane (side panels) Lightweight 4.4 oz. Unavail.
REI Co-op Lightweight Crew $40 92% polyester, 8% spandex Lightweight 6.5 oz. Unavail.
Icebreaker Oasis Crewe $95 100% merino wool Midweight 8.9 oz. 200g/m²
Ortovox 185 Rock'N'Wool LS $110 100% merino Light/mid 6.9 oz. 185g/m²
Norrøna Wool One-Piece $199 89% merino, 11% nylon Midweight 14.1 oz. 170g/m²
Mountain Hardwear Ghee Hoody $80 85% polyester, 15% elastane Lightweight 7.9 oz. Unavail.
L.L. Bean Silk Crewneck $50 100% silk fabric Lightweight Unavail. Unavail.


Baselayer Buying Advice

Baselayer Materials

Merino Wool
Merino wool, despite a higher cost than synthetics, is our recommended baselayer material for a number of reasons. It’s ultra soft and comfortable, has superior temperature regulation, and resists odor. Granted, merino wool baselayers are expensive and less durable than the polyester competition, amounting to roughly double the cost. Take good care of them, however, and you should be able to get at least a few seasons of extended use. Our top baselayer pick, the Smartwool Merino 250 ¼ Zip, is 100 percent merino. For more information about the pros and cons of the material, check out our article: Merino Wool: Is It Worth It?

Baselayers (Smartwool 250 in tent)
The Smartwool Merino 250 is 100-percent merino

For a cost-effective baselayer alternative, you can always turn to polyester. Led by Patagonia’s legendary Capilene line, polyester fabrics can keep up in terms of moisture wicking and the comfort difference isn’t that far off. The downside is stink prevention, which is an area of emphasis for many manufacturers. Thus far, odor-resistant polyesters still can’t compete with the natural benefits of merino but they are improving. In addition, polyester fabrics don’t regulate temperatures as well, so it’s more important to match the fabric weight with intended use and conditions (more on that below). Despite the downsides, polyester fabrics are what we recommend most often for resort skiers. At approximately half the price of a comparable merino option, the cost saving is too significant to overlook.

It’s not quite as simple as deciding between an all-merino or all-polyester baselayer. Some performance-oriented brands are experimenting with blends that aim to offer the comfort and performance of merino wool with the durability and moisture-wicking of polyester. The Patagonia Capilene Air, for example, weaves together 51-percent merino wool with 49-percent polyester, while Black Diamond's NuYarn (as seen in the Solution 150 Merino) actually wraps merino fibers around a nylon core, and then weaves this manufactured thread together with polyester. The commonality of these types is that they are among the highest priced items in this market, so these blends are more about performance than cost savings.

Baselayer (Patagonia Capilene Air)
Wearing Patagonia's Capilene Air while ice climbing near Canmore, Alberta

Silk is one of the softest and most comfortable of the baselayer fabrics and packs an impressive amount of warmth into a lightweight, thin design. But as the demand for temperature-regulating baselayers rises, silk is largely going out of vogue. It just can’t keep up with merino or polyester in terms of moisture wicking and turns into a sweat lodge during high-output activities. Moreover, silk is far less durable than polyester and should always be worn under a mid or outer layer to protect from UV rays and abrasion. And finally, it does not resist odor like merino and should be hand-washed. We only include one silk option on our list for a reason, but it does have its advantages as a dedicated sleep shirt or extra layer in town.

Important Strengths and Weaknesses

The breathability of a baselayer is dependent on a number of factors, including the type and quality of the fabric, thickness, and openness of the weave. In general, lightweight merino wool will offer the best in terms of breathability, although some high-quality lightweight synthetics are close. This means that for high-exertion activities where you will be working up a sweat (think ski touring, cross-country skiing, biking, and climbing) it’s probably worth spending more to get a higher-performing baselayer like the merino Smartwool 150 or synthetic Patagonia Capilene. Craft’s Active Extreme baselayer is another very thin, very breathable synthetic option. Spending less, particularly on a thick baselayer, will yield less breathability. Whether or not that’s a deal-breaker is up to personal preference and your tendency to overheat.

Merino: Excellent
Blends: Excellent
Polyester: Very good 
Silk: Not good

Baselayer (climbing)
Breathability is important for high-output activities

Odor Prevention
Merino wool excels at pulling moisture away from your skin, and less sweat build up means less stink build up. If you’re taking an extended backcountry trip and don’t want to carry multiple baselayers or rinse them each night, merino is the way to go. Some synthetics do fine for odor prevention, provided you aren’t working up a huge sweat. For example, we’ve hiked for extended periods in Patagonia’s Capilene in cool weather and have been impressed with its odor resistance. But nothing beats merino in keeping you dry and stink free.

Merino: Very good
Blends: Good
Polyester: Not good
Silk: Not good

Baselayers (Black Diamond Solution Merino 150)
Getting ready to hike in the Black Diamond Solution 150 merino baselayer

Here is where the tide changes: merino is super soft but prone to developing small holes over time that eventually hamper the performance of the product, whereas synthetics should last for multiple seasons. To put this in perspective, we usually get a season or two out of a standard lightweight merino baselayer, even from the top brands and by following their washing instructions (cold water and line dry). Admittedly, these shirts get a lot of use, but that’s still a very short lifespan. But with synthetics, one or two seasons would be on the short end of the spectrum and we would hope for more like three or four.

Some companies are blending wool and synthetics to increase the strength of the baselayer without compromising next-to-skin comfort, which is a good idea in our opinion. We haven’t noticed much of a drop in terms of comfort or performance, but merino/synthetic blends are a step up in durability. Even so, if we’re wearing a baselayer without anything overtop, we’ll always opt for a fully synthetic piece such as the NW Alpine Spider Hoody.

Polyester: Excellent
Blends: Very good
Merino: Not good
Silk: Not good

Baselayers (climbing in the NW Alpine Spider Hoody)
Climbing in the ultra-durable NW Alpine Spider Hoody

Out of all the fabrics we’ve mentioned, merino has the best heat-trapping properties. In general, you get a better warmth-to-weight ratio with merino than with polyester, and it regulates temperature better too. The same shirt that keeps you warm in the winter will keep you cool when you’re sweating up the skin track in the shoulder seasons. Silk, too, is noticeably warm for its thin makeup, but its lack of breathability is a strong drawback. It’s also important to consider if you’ll be wearing your baselayer as an outer layer—while merino doesn’t do much to block wind, some polyester fabrics (such as Patagonia’s Capilene) are so tightly woven that they have the ability to resist light gusts. And keep in mind that warmth is directly related to the thickness of the material too, which we discuss in the Insulation Weight section below. 

Merino: Excellent
Blends: Very good
Polyester: Good
Silk: Good

Baselayer (with midlayer)
Merino wool offers excellent warmth

Baselayer Categories: Insulation Weight 

Logically, lightweight baselayers are the best breathers but do the least in keeping you warm. This is where merino wool shines—it does an admirable job of temperature regulation for the weight and thickness. However, the thinner the merino, the less durable it becomes. For this reason, most lightweight baselayers are made of polyester. These are ideal for early season skiing, bluebird days, and high-output activities such as cross-country skiing and cold-weather running. Resort skiers and winter climbers will likely opt for a warmer and cozier midweight baselayer.

For the widest variety of conditions, a midweight baselayer makes the most sense. It will provide the warmth you need yet still be breathable enough for physical exertion, especially when made with high-quality merino or polyester. Midweight baselayers are the most popular choice for downhill skiers: they’re plenty warm for the lift ride up but you are unlikely to overheat on the descent. They are less popular than lightweight baselayers for hiking or ski touring in moderate conditions as the extra warmth corresponds with a drop in the fabric’s ability to regulate temperatures (even merino can get too hot in warm temperatures). But in cool spring and fall conditions, a midweight baselayer can perform great as an outer layer and is the ideal next-to-skin layer for resort skiing on cold days.

Patagonia Capilene Midweight baselayer with Arc'teryx Macai ski jacket
Layering for skiing with the Patagonia Capilene Midweight

Heavyweight baselayers are specialty items for cold temperatures or if you’ll be relatively sedentary. The extra thickness inhibits breathability and it’s easy to start sweating even on short walks. Keep in mind that you don’t need all of your insulation from a single article of clothing, and as a result, you can always add warmer layers on top of a light or midweight baselayer. But for winter mountaineering, extreme cold, or low-output activities around camp, a heavyweight baselayer can be the height of coziness. If you do go this route, we love the Woolx Glacier LS Heavyweight, which is a 400g/m² all-merino baselayer that still breathes decently well. Patagonia’s Thermal Weight Capilene can get swampy unless it’s very cold.

Crew Neck vs. Quarter or Half Zips

Nearly every baselayer on the market is made in a number of styles, including long-sleeve crew and half/quarter-length zippered shirts. Many folks opt for a crewneck style, but there are a number of reasons to think about a zippered shirt. One upside is the ability to adapt to changing weather conditions. Zip up for added warmth at the start of the climb, and unzip as you work up a sweat. And if you want to remove the shirt altogether, it’s nice not having to take off your helmet to do so. Furthermore, the extra coverage you get with the raised collar is a nice boost in warmth, and we’ve even found that quarter or half-zip long sleeves have a decent look for around town. The downside is the collars can flop around if you unzip the shirts while running, and having a zipper on your next-to-skin layer isn’t as comfortable as the cleaner crew style.

Baselayer (Smartwool)
A lightweight crew-neck baselayer


For optimal performance, baselayers need to have a snug fit. This helps the fabrics draw moisture away from your skin most efficiently. Some folks like wearing their baselayers for casual use, and that’s when a dedicated performance product like Craft Active Extreme is less useful. The shirt conforms to your body like a performance piece should, but it’s far too tight to wear anywhere else. A product like the REI Co-op Merino Midweight Half-Zip is on the opposite end of the spectrum, with a roomier fit that sacrifices a little in moisture wicking and breathability. But it’s a great choice for those that prefer a dual use baselayer/casual shirt. In the end, your decision is a personal one, and we recommend looking at fit based on intended use and preferences on style.

Key Baselayer Features

Baselayers can range from simple, featureless crew tops like the Icebreaker Oasis to hooded half-zips with a chest pocket (the NW Alpine Spider Hoody, for example). If you know you’ll be layering a mid or outer layer over your baselayer, the simpler the better. However, those who wear their baselayer as an outer layer will appreciate zip pockets and thumb loops. And climbers and skiers will benefit from a tight hood or balaclava that fits under their helmet. Furthermore, some baselayers even have the capability of blocking sun rays (measured by the UPF rating). As usual, it will help to identify what you’ll be using your baselayer for before determining what features you need.

Baselayer (thumb strap)
Thumb straps are handy for keeping sleeves in place

What About Baselayer Bottoms?

Most baselayers on this list have a matching bottom with the same construction and a similar or identical price. For organization sake, we list the tops here as they are more popular, but the bottoms are readily available and share the same pros and cons. In general though, maintaining a warm core will do much more for your entire body’s comfort than keeping your legs warm. But given that there’s no need to choose—and provided that almost nothing is cozier than a pair of long johns—we’re huge proponents of baselayer bottoms as well.

Baselayers (Smartwool 250)
For cold nights outside, baselayer bottoms offer great warmth

Layering Systems: Base, Mid, and Outer Layers

To get the most out of your technical clothing, it’s important think of everything as a system. Each piece relies on the layers around it to perform well. As an example, if you have a baselayer that wicks moisture well, but are wearing a fully rubber mid or outer layer, it won’t matter how nice of a merino fabric you have: you’ll still be wet and miserable. As such, take the time to put together mid and outer layers that are as high-performing as the baselayers listed above.

Baselayers have two primary functions: warmth and moisture wicking. Whether constructed with silk, wool, polyester, or a blend, a baselayer is made to retain your body’s heat while transporting moisture away from the skin. And these two features work together—keeping the body dry will in turn lead to more warmth. Baselayers are worn beneath a midlayer or shell during the winter months, or as an outer layer during the fall and spring for activities like hiking, biking, and climbing. The thickness and material of your baselayer will have big impacts on warmth and breathability, so make sure to keep this mind when making a purchase. 

Baselayers (Patagonia Capilene Air underneath synthetic jacket)
A warm combination: Patagonia Capilene Air and Arc'teryx Nuclei FL

For high-output activities, such as hiking, backpacking and climbing, breathability is top priority. We recommend a fleece jacket or synthetic jacket for balancing warmth and ventilation. High performers include the Arc’teryx Atom LT and the R line of fleeces from Patagonia. If you only plan to grab your insulating layer during downtimes, such as hanging around camp after the sun goes down, consider a warm and super packable down jacket. Skiing is a similar story, and conditions will dictate the best midlayer for you. Options can range from a puffy down jacket to a light fleece.

Outer Layers
Outer layers are the most specialized part of the system, and their complex designs can get quite pricey. A waterproof, breathable, and packable rain jacket is needed for activities like climbing and hiking/backpacking. Winter conditions are much harsher, so durability takes precedence for ski jackets. Their designs offer more pockets for storing gear or personal effects and a longer fit to protect you from snow sneaking through. There are also hardshell jackets that blur the lines, mixing the weight of a rain jacket with the performance (and extra cost) of a ski jacket.
Back to Our Top Baselayer Picks  Back to Our Baselayer Comparison Table

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