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 2018. For more information, see our baselayer comparison table and buying advice below the picks. To complete your kit, we’ve also written about the best midlayers and ski jackets
 

1. Smartwool Merino 250 1/4-Zip ($100)

Smartwool NTS 250 Zip T baselayer (2017-2018)Materials: 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% 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

 

2. Patagonia Capilene Midweight Zip-Neck ($69)

Patagonia Capilene Midweight (2017-2018)Materials: 100% polyester
Category: Midweight
Weight: 7.5 oz.
What we like: More durable and cheaper than merino.
What we don’t: Not quite as soft.

Choosing synthetics over merino wool has clear upsides, the most notable being cost and durability. For $31 less than 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 seven years old and counting despite heavy use.

What do you sacrifice by going with a synthetic baselayer over merino? Polyester is decently comfortable but not as soft against the skin, and it doesn’t repel odor as well as wool. This doesn’t mean that your Capilene will get stinky super quickly, 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 a number of synthetic options in 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

 

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

REI Co-op Merino Midweight Half-Zip baselayerMaterials: 100% merino wool
Category: Lightweight
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. We’ve used it for everything from backpacking to cross-country skiing and came away impressed. 

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 Crew, although you do get a front zip and higher collar on the REI. And for just $10 more, you can get the legendary Smartwool Mid above, out 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 Co-op Merino Midweight  See the Women's REI Co-op Merino Midweight

 

4. Helly Hansen Lifa Stripe Crew ($40)

Helly Hansen Dry Stripe Crew baselayerMaterials: 100% polypropylene
Category: Lightweight
Weight: 4.2 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

 

5. Arc’teryx Satoro AR Zip-Neck ($139)

Arc'teryx Satoro AR baselayer (2017-2018)Materials: 81% merino wool, 12% nylon, 7% elastane
Category: Midweight
Weight: 6.9 oz.
What we like: Merino softness with added durability.
What we don’t: Expensive.

Arc’teryx always seems to take outdoor gear tech to the next level, and the new Satoro AR is a case in point. Everyone loves the softness of merino against the skin, but its durability has long been an issue. The Satoro attempts to solve the problem by using a nylon core with merino wrapped around the outside. The result is a baselayer that still offers premium next-to-skin comfort but is much tougher than pure merino.

Arc’teryx also paid attention to a number of small details with the Satoro AR. The cuffs are nicely tailored and long for additional warmth over the hands. Gusseted underarms increase mobility, and a laminated zipper pocket on the chest for men (arm for women) adds to its utility as an outer layer. The result is a premium baselayer at a premium price, and whether all that technology is worth it is up to you... Read in-depth review
See the Men's Arc'teryx Satoro AR  See the Women's Arc'teryx Satoro AR

 

6. NW Alpine Spider Hoody ($119)

NW Alpine Spider Hoody baselayerMaterials: 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 four years of climbing abuse—much of the time without a jacket overtop—and it has yet to develop any holes or tears. 

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, $119 is a hefty price tag for a polyester baselayer. However, impressive durability—and features like a balaclava hood and chest zip—set the Spider Hoody apart as a highly functional and long-lasting piece. 
See the Men's NW Alpine Spider  See the Women's NW Alpine Spider

 

7. Craft Active Extreme Crewneck 2.0 ($80)

Craft%20Active%20Extreme%202.0%20baselayer.jpgMaterials: 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

 

8. WoolX Glacier LS Heavyweight Crew ($100)

WoolX Glacier LS Heavyweight baselayerMaterials: 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% 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 extremely 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% merino and both are $100. This means that you’re getting much more baselayer for your money from WoolX compared to 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 Men's WoolX Glacier LS  See the Women's WoolX Alpine

 

9. Patagonia Capilene Air Hoody ($149)

Patagonia%20Capilene%20Air%20baselayer.jpgMaterials: 51% merino, 49% polyester
Category: Midweight
What we like: Amazing warmth in a tiny package; responsibly sourced wool.
What we don’t: Very expensive and not useful as an outer layer.

Patagonia’s long-lost Merino Air is back, and with a brand new name: the Capilene Air. Known for leading the charge in their dedication to sustainable environmental practices, Patagonia took a multi-year hiatus from wool to revamp their supply chain and develop a new standard for sourcing. 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 the polyester make-up of the Capilene Air gives it a bump in durability, we’ve noticed that the material snags easily and has developed runs. Furthermore, it is noticeably permeable to wind. For these reasons we don’t recommend wearing the Capilene Air without a layer overtop. 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

 

10. Icebreaker Oasis Crew ($90)

Icebreaker Oasis Crew baselayerMaterials: 100% merino wool
Category: Lightweight
Weight: 8.2 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 Crew from Icebreaker is as versatile as any baselayer on this list. It’s made from 100% 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% 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

 

11. REI Co-op Lightweight Base Layer Crew ($35)

REI Lightweight Baselayer (2018)Materials: 100% polyester
Category: Lightweight
Weight: 6.0 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 $35, this REI Lightweight Crew offers most of the performance of the more expensive options above in a simple yet functional design. With the matching bottoms, you have a full long underwear kit for way less than $100, which cheaper than just a merino top from Smartwool.

What are the downsides? We’ve found the lightweight model works well for mild resort skiing days and casual use, but you may not be warm enough on frigid days. And although the fabric is soft in a silky kind of way, it can’t compete with merino or even Patagonia Capilene in softness and comfort (older versions had a softer brushed interior that we prefer to the current iteration). 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

 

12. Arc’teryx Phase AR Zip-Neck ($89)

Arc'teryx Phase AR (2017-2018)Materials: 100% polyester
Category: Midweight
Weight: 6.2 oz.
What we like: Great performance for a synthetic.
What we don’t: A merino-like price tag.

In terms of synthetic baselayers, you won’t find better quality than the Phase AR from Arc’teryx. Built with Phasic AR (All-Round) polyester, you get excellent breathability and moisture wicking for a synthetic, along with an athletic fit that moves well and is lightweight at only 6.2 ounces. The Phase AR is a great baselayer for hiking in fall and spring conditions and works well under a shell in the winter. You may want a more breathable piece for certain high-output activities like running and cross-country skiing, but it’s a nice option for downhill skiing and walking in the shoulder seasons.

As always, Arc’teryx falls at the high end of the price spectrum and tops Patagonia’s Capilene Midweight by a full $20. Many serious outdoorspeople swear by Arc’teryx from a performance perspective, but it’s not for the faint of heart. If you spend a lot of days on the mountain each year and get a lot of use out of your gear, the Phase AR may very well be worth it.
See the Men's Arc'teryx Phase AR  See the Women's Arc'teryx Phase AR

 

13. Fjallraven High Coast First Layer ($100)

Fjallraven%20High%20Coast%20First%20Layer.jpgMaterials: 50% merino, 50% polyester
Category: Heavyweight
Weight: 16.9 oz.
What we like: Classy looks and high quality heavyweight blend.
What we don’t: Too warm for most activities.

We’ve learned to count on Fjallraven for stylish, high quality outdoor clothing, and their High Coast First Layer is no exception. This simple, ribbed-knit baselayer is attractive and form fitting, and comes in classy colorways—making it just as suitable for the city as on the trail. The heavyweight merino/polyester blend is a nice compromise between the 100% merino WoolX Heavyweight above and the 100% synthetic Under Armour Base 4.0 below. It’s durable but still soft and odor-resistant. Plus, the High Coast’s fit is somewhere in between too—not too boxy, and not too tight.

Fjallraven doesn’t give a g/m² specification, but at 16.9 ounces, the High Coast is among the heaviest baselayers on our list (it’s even billed as a “sweater”). There’s certainly a time and place for an extra warm next-to-skin layer, but we won’t be toting the High Coast into the backcountry or wearing it during high-output activities. The Fjallraven is most comfortable around town and as a cold-weather skiing piece.
See the Men's Fjallraven High Coast  See the Women's Fjallraven High Coast LS

 

14. Norrøna Wool One-Piece ($219)

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

 

15. Under Armour UA Base 4.0 Crew ($85)

Under Armour Base 4.0 baselayerMaterials: Polyester/elastane
Category: Heavyweight
What we like: Very warm and durable.
What we don’t: Snug fit isn’t as versatile.

Under Armour practically built their reputation on baselayers, so it shouldn’t come as a surprise that they have an impressive lineup for winter sports. To start, they offer a ton of warmth options—most brands include two or three different weights, but the UA Base ups that to four. We’ve included their warmest version here, the synthetic Base 4.0, which has Under Armour’s classic snug fit and is a great match for frigid days and those that run cold.

In comparing the UA Base 4.0 to another heavyweight on our list, the WoolX Glacier above, it’s a classic showdown of synthetic vs. merino wool. The WoolX is softer to the touch, doesn’t develop stink as quickly, and isn’t as prone to overheating. On the flip side, the Under Armour is more durable, wicks moisture well for its thick construction, and saves you $15. For us, the WoolX gets the edge with its nicer feel and less fitted cut that allows it to be worn as a standalone piece. But if you want a super warm synthetic baselayer with a performance fit, the UA Base 4.0 is a fine option.
See the Men's Under Armour Base 4.0  See the Women's Under Armour Base 4.0

 

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

L.L. Bean Silk Underwear Crewneck baselayerMaterials: 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

 

17. The North Face Warm Zip-Neck ($60)

The North Face Warm Zip-Neck baselayerMaterials: 100% polyester FlashDry Eco
Category: Midweight
Weight: 8.8 oz.
What we like: Front zip is handy for releasing heat.
What we don’t: Taller collar gets in the way when unzipped.

For resort ski days or sliding into your sleeping bag on a chilly backpacking trip, the North Face Warm Zip-Neck is a nice budget synthetic. Its polyester fabric offers comparable wicking properties to the merino baselayers on this list but at a cheaper price. The FlashDry Eco fabric does a decent job at resisting odor, but still falls short of any merino design. And of course, next-to-skin comfort isn’t quite as high as wool but you get a welcome bump in durability.

With any synthetic baselayer, we prefer the half zip over the crew, which helps compensate for the fabric’s marginal ability to regulate heat. Our main issue with The North Face Warm Zip-Neck is that it’s similar in cost to Patagonia’s Capilene line but we have more confidence in the build quality and performance of the latter. If the $10 matters or you find this baselayer on sale, go for it. Otherwise, we give the nod to the Capilene.
See the Men's North Face Warm Zip Neck  See the Women's North Face Warm Zip Neck

 

Baselayer Comparison Table

Baselayer Price Materials Category Weight g/m²
Smartwool Merino 250 1/4-Zip $100 100% merino wool Midweight 10 oz. 250g/m²
Patagonia Capilene Midweight $69 100% polyester Midweight 7.5 oz. 160g/m²
REI Merino Midweight Half-Zip $90 100% merino wool Midweight 8.5 oz. 200g/m²
Helly Hansen Lifa Stripe Crew $40 100% polypropylene Lightweight 4.2 oz. 125g/m²
Arc’teryx Satoro AR $139 81% merino/12% nylon/7% elastane Midweight 8.1 oz. 180g/m²
NW Alpine Spider Hoody $119 92% polyester/8% spandex Midweight 11 oz. 194g/m²
Craft Active Extreme Crewneck 2.0 $80 100% polyester Lightweight 4.4 oz. Unavail.
WoolX Glacier LS Heavyweight $100 100% merino wool Heavyweight 16 oz. 400g/m²
Patagonia Capilene Air Hoody $149 51% merino/49% polyester Midweight Unavail. Unavail.
Icebreaker Oasis Crew $90 100% merino wool Lightweight 8.2 oz. 200g/m²
REI Co-op Lightweight Crew $35 100% polyester Lightweight 6 oz. Unavail.
Arc’teryx Phase AR Zip-Neck $89 100% polyester Midweight 6.2 oz. Unavail.
Fjallraven High Coast First Layer $100 50% merino/50% polyester Heavyweight 16.9 oz. Unavail.
Norrøna Wool One-Piece $219 89% merino/11% polyester Midweight 14.1 oz. 170g/m²
Under Armour UA Base 4.0 $85 Polyester/elastane blend Heavyweight Unavail. Unavail.
L.L. Bean Silk Crewneck $50 100% silk fabric Lightweight Unavail. Unavail.
The North Face Warm Zip-Neck $60 100% polyester FlashDry Eco Midweight 8.8 oz. 180g/m²

 

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% merino. For more information about the pros and cons of the material, check out our article: Merino Wool: Is It Worth It?

Polyester
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.

Baselayer with Down Sweater
A warm combination: Patagonia Capilene and Patagonia Down Sweater

Blends
It’s not quite as simple as deciding between an all-merino or all-polyester baselayer. Some performance-oriented brands like Arc’teryx are experimenting with blends that aim to offer the comfort and performance of merino wool with the durability of polyester. One example is the Arc’teryx Satoro AR, which has a nylon core for durability wrapped in merino for next-to-skin comfort and odor resistance. 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.

Silk
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

Breathability
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 all-merino REI Midweight 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 SmartWool
Lightweight baselayers breathe well when you're working hard

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
 

Durability
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

Arc'teryx Satoro AR (backpack)
The Satoro AR is one of the most durable merino wool blends available

Warmth
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 Categories: Insulation Weight 

Lightweight 
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.

Midweight
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.

Arc'teryx Satoro AR (climbing skins)
Ski touring in the midweight Arc'teryx Satoro AR

Heavyweight
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, 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. 
 

Fit

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 Fjallraven High Coast First Layer 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 thumb loops and 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.
 

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%20(climbing).jpg
A well-thought-out layering system is essential in demanding conditions

Baselayers
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. 

Midlayers
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.
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