The 7 Best Base Layers for Women

Best Merino Wool Base Layer

Black Diamond Solution 150 Merino Quarter Zip - Women's

Material: 78% Merino wool, 22% polyester | Thickness: Lightweight

Meet your new favorite base layer: the Black Diamond Solution 150 Merino Quarter Zip combines the strength, durability, and wicking performance of polyester with the exceptional comfort and odor-resistant abilities of Black Diamond's innovative Nuyarn Merino stretch wool technology. We were especially impressed by the overall strength and durability of this unique fabric combination when we accidentally snagged our layer on a sharp branch during a backcountry ski tour. Rather than rip a hole that ran like pantyhose, the hole never increased in size, even after multiple seasons of use. The layer features a slim and flattering fit that is both highly breathable and incredibly versatile, thanks to a hood, a quarter zip at the neck, and thumb loops that help to either maximize your warmth or shed excess body heat and sweat when pushing hard. Few others outscored it for warmth, and those that did performed less well in other areas. For example, our favorite synthetic base layer, the Arc'teryx Rho Hoody, delivers excellent warmth, but it isn't quite as breathable and cannot come close to matching the Solution 150 on odor retention. Other options, like the Icebreaker 260 Tech Long-Sleeve Half-Zip and Smartwool Classic Thermal Merino 1/4 Zip, excel at keeping you warm and can manage odor with classic Merino ease, but just don't keep up in most other metrics.

While our testing team was initially skeptical of the Black Diamond Solution 150 Merino Quarter Zip's stiffer Merino wool construction, it quickly became our go-to for everything from backcountry skiing to multi-pitch rock climbing and everything in between. We found that with each additional wash and wear, the fabric softened for a more comfortable next-to-skin feel — something we've come to expect from any primarily Merino wool design. The lightweight construction offers an outstanding warmth-to-weight ratio through top-notch thermoregulation and breathability. Designed with the adventure enthusiast in mind, this layer is the clear winner when it comes to year-round mountain pursuits. For a layer with comparable breathability and comfort at a lower price, you might consider the Smartwool Classic All-Season Merino. While it isn't quite as warm as the Black Diamond Quarter Zip, it will save you some money and makes an excellent lighter-weight addition to any winter kit. Or if you need something warmer and cost takes priority over other performance needs, take a look at the extremely well-priced Merino.tech Merino Crew.

Read more: Black Diamond Solution 150 Merino Quarter Zip review

Best Synthetic Base Layer

Arc'teryx Rho Hoody - Women's

Material: 84% polyester, 16% elastane | Thickness: Midweight

We've tested versions of the Arc'teryx Rho Hoody over many years, and it still stands out as our go-to synthetic for all technical missions. The interior is fleece lined with wicking power that does a good job of moving moisture away from the skin. We love the fitted design, which is stretchy and incredibly easy to layer, plus the neck warmer, hood, and full-face balaclava, which offers versatile warmth and protection from the elements. The hood even has a small opening for a ponytail to reduce bulk. This is one of the most versatile base layer tops we've tested, performing well from ski tours in Colorado to mega rafting missions in the Grand Canyon. As is true with most synthetics, wear and tear is minimal, even after being put through the wringer. Tried, tested, and truly awesome.

To benefit from the increased levels of comfort and warmth due to the fleece lining on the interior of this base layer, you must sacrifice a certain amount of breathability and anticipate a bit more odor retention. But when it comes to the Rho Hoody, we suggest using this drawback to your advantage. Rather than focusing solely on how you will layer it, consider wearing this top as a stand-alone piece during the change of seasons to create a barrier between your sensitive skin and those cold northern winds. Or, if you're seeking a top that better balances warmth and breathability and you are game to try a Merino-synthetic blend, you will want to take a look at the similarly priced Black Diamond Solution 150 Merino Quarter Zip. Another option is to sacrifice a degree of warmth for a big step up in breathability. If that's the right recipe for you, the Patagonia Capilene Thermal Weight Zip-Neck is a great option to consider. It's worth noting that the Rho Hoody is more expensive than other synthetic options. However, given that it is one of the most time-tested pieces we've had the opportunity to use, the performance value you get out of it is definitely worth the investment. That said, the Rho Hoody is best for someone seeking a synthetic layer that's durable, technical, and looks great to boot. If budget is a constraint, the REI Co-op Midweight Base Layer Crew is an excellent value for a high-quality synthetic.

Read more: Arc'teryx Rho Hoody review

Best Value for Merino

Smartwool Classic All-Season Merino - Women's

Material: 88% Merino wool, 12% nylon | Thickness: Lightweight

The Smartwool Classic All-Season Merino is a super lightweight base layer that's available for a more affordable price and would be a great addition to any activity-heavy winter wardrobe. Constructed from 88% Merino wool and 12% nylon, it is one of the lightest base layers that we've tested. Yet the core-spun nylon enhances both its durability and the overall structure of the layer, making it a great choice under a bib for regular runs on your ski hill or as a top when hiking on crisp fall days. The naturally odor-free Merino keeps the layer fresh, even when worn multiple times between washes, and the combination of both merrow stitch and flatlock seams prevents chafing when worn beneath a heavy backpack.

The thin jersey Merino-nylon blended fabric of the Smartwool Classic All-Season Merino is highly breathable, quick-drying, and easy to layer. Our testing team was impressed with this top's ability to wick moisture, especially when positioned beneath mid and outer layers during high-intensity training sessions. But it isn't the cheapest Merino option out there, and it may still be more high-performance than some shoppers really need. If you're not in need of a base layer that can live up to high-intensity use over a long winter playing outside, there are even more affordable options, especially if you are willing to sacrifice some degree of wicking performance. In that case, we'd suggest you check out the notably lower cost Merino.tech Merino Crew | Merino.tech Merino Crew. But, if you plan to keep moving throughout winter, breathability and wicking are likely more essential considerations. In that case, the All-Season is our preferred budget-friendly choice, perfect as the base for a cold-weather layering system or as a stand-alone piece during the cooler months of the year. If Merino fabric is just not your thing due to allergy or preference, the REI Co-op Midweight Base Layer Crew is a great low-cost synthetic option that is worth a careful look.

Read more: Smartwool Classic All-Season Merino review

Best Synthetic Bang for Your Buck

REI Co-op Midweight Base Layer Crew - Women's

Material: 92% polyester, 8% spandex | Thickness: Midweight

The REI Co-op Midweight Base Layer Crew is a great choice for those seeking a highly functional synthetic base top with an affordable price tag. This garment offers enough warmth for those in-between-season days and is available for a fraction of the cost of most Merino options and its top-performing synthetic competitors like the Arc'teryx Rho Hoody or Patagonia Capilene Thermal Weight Zip-Neck. It also has useful design elements and durable features, such as flatlock seams and thumb loops, that give us confidence this layer will be a reliable part of our winter wardrobe for many seasons to come.

Like with many synthetic base layers, we were disappointed by the odor retention of the REI Co-op Midweight Base Layer Crew's polyester blended fabric, as we noticed it held onto odor almost immediately when put to use. No synthetic options we've tested do a great job of avoiding this problem, but Merino and Merino-synthetic blends, like the Black Diamond Solution 150 Merino Quarter Zip or Ridge Merino Convict, generally perform better overall. So, it's a trade-off one must consider. Also, while the REI Midweight Crew's fabric successfully wicked moisture and sweat away from our skin, it couldn't efficiently release moisture at a similar pace through the tightly woven fabric, so it took longer to dry. This sometimes meant sacrificing precious warmth during colder temps, which is not what you look for out of your gear when you are going hard. For this reason, we do not recommend the REI Midweight Crew for high-output activities or for the depths of winter. But, overall, our testers were very happy with the slim-fitting, durable design that kept us warm during the shoulder seasons or as the base of our layering system for moderately cold weather adventures. If you find odor retention to be really off-putting, consider investing in a Merino top like the Icebreaker Merino 200 Oasis Crewe.

Read more: REI Co-op Midweight Base Layer Crew review

Best Merino on a Tight Budget

Merino.tech 250 Crew - Women's

Material: 100% Merino wool | Thickness: Midweight

The Merino.tech Merino Crew is the super low-budget option we would recommend to anyone who needs a warm top for a quick ski trip or other winter getaway but isn't necessarily looking to build out a cold-weather wardrobe for regular use. Although this midweight crew is not our favorite cost-saving choice for high-intensity cold-weather sports or frequent use, it is constructed from a nice, thick 100% Merino wool — 17.5-micron, 250 g/m² ultra-fine fibers — that delivers welcomed additional warmth on cold days. The thicker fabric also increases the durability of this layer, ensuring it is noticeably more resistant to micro holes and tears, even if it is not quite as soft as other options next to the skin. The relaxed fit is true to size and easy to layer over the top, making it an easy, low-cost choice for the occasional resort turn, shoulder season hike, or a relaxed winter day at home by the fire. Another favorite of our testing team that also features a relaxed yet true-to-size fit is the REI Co-op Midweight Base Layer Crew. This synthetic option sells at an equally low price and is even easier to layer other items over the top due to its smooth synthetic interface and stretchy fabric.

While the fit is true to size, we couldn't help but notice that the thick, aesthetic seams, especially at the wrist, can feel restrictive and even abrasive if you'd like to be able to pull up your sleeves throughout the day. The thickness of this layer also requires a longer drying time, delivering a less breathable performance when you start to sweat on the move. If you're after a base layer that is versatile enough to be worn as a stand-alone piece or makes an excellent base for layering over the top, allow us to point you to the well-priced, high-performance Smartwool Classic All-Season Merino. The All-Season would make a great, versatile addition to any ski, board, or climbing kit, thanks to its top-notch wicking performance. Or, for a bump in cost, consider the Icebreaker Merino 200 Oasis Crewe, which is super soft, toasty, and impressively sport-ready. However, for anyone who lives in warmer climates or is city-based and unlikely to require a reliable layer for demanding mid-winter outings, the Merino.tech is a solid, inexpensive, and budget-friendly layer that will serve just fine whether you're lounging around the cabin or pursuing low-output cold weather activities.

Read more: Merino.tech Merino Crew review

Best Thermal Crew

Icebreaker Merino 200 Oasis Crewe - Women's

Material: 100% Merino wool | Thickness: Lightweight

The Icebreaker Merino 200 Oasis Crewe quickly stood out from the competition thanks to its superior fit and super soft 100% Merino wool design. Ultrafine 18.9-micron fibers are tightly woven together to create a layer that successfully traps heat and wicks moisture away from the body. Our testers love the thoughtful design that includes strategically placed flatlock seams that increase comfort and durability and gusseted underarms to allow for better mobility.

Perhaps our biggest complaint about this crew is the limited breathability when layered in a system. The Oasis can wick sweat away from the body but has trouble releasing sweat from the fabric when not exposed to fresh air. We also couldn't help but notice the slower drying speed of the Oasis (one hour in the spring sun) during our spring testing period. If you want a layer that dries faster, the Patagonia Capilene Thermal Weight Zip-Neck or Ridge Merino Convict are great choices. However, after evaluating several different crew designs and materials, we found that this high-performing Icebreaker layer quickly climbed to the top of our list. We attribute this stellar performance to its soft yet durable Merino wool, a great fit that promotes mobility, and its durable construction that limits any chafing or friction while getting after it in the mountains.

Read more: Icebreaker Merino 200 Oasis Crewe review

Best for Midweight Breathability

Patagonia Capilene Thermal Weight Zip-Neck - Women's

Material: 92% recycled polyester, 8% spandex | Thickness: Midweight

The Patagonia Capilene Thermal Weight Zip-Neck quickly stood apart from the competition in terms of warmth and breathability. Our lead tester loves this layer as a stand-alone piece for efficiently shedding sweat accumulated on fall trail runs, as well as the base of her cold weather kit while rock climbing during those crisp October nights. While not a thermal weight as advertised, the polyester blended fabric and micro-grid fleece interior gave a memorable performance in terms of exceptional breathability and moisture-wicking capabilities.

Patagonia advertises a Polygiene odor control treatment for the Capilene Thermal, but we found this layer retains body odor almost immediately, especially when used several days in a row. Again, a natural Merino layer like the Mons Royale Cascade Merino Flex Mock Neck LS will serve you better if you find odor retention particularly offensive. And while we appreciate the thumb loops on the Capilene Thermal in terms of layering ability, the low-quality construction (basically just an elastic band) doesn't inspire confidence they will last for the life of the base layer. That said, this layer offers excellent thermoregulation and breathability thanks to the air-permeable Polartec fabric and the long zip neck. These work together to effectively dump heat and excess sweat during those high-intensity mountain pursuits.

Read more: Patagonia Capilene Thermal Weight Zip-Neck review

Compare Products

Compare select up to 5 products to compare

	Score	Product	Price
	84	Black Diamond Solution 150 Merino Quarter Zip - Women's Best Merino Wool Base Layer	$145
	83	Ridge Merino Convict - Women's	$150
	82	Arc'teryx Rho Hoody - Women's Best Synthetic Base Layer	$120
	79	Icebreaker Merino 200 Oasis Crewe - Women's Best Thermal Crew	$105
	76	Patagonia Capilene Thermal Weight Zip-Neck - Women's Best for Midweight Breathability	$109
	76	Ridge Merino Aspect Midweight - Women's	$75
	75	Mons Royale Cascade Merino Flex Mock Neck LS	$120
	75	Smartwool Intraknit Thermal Merino - Women's	$130
	72	REI Co-op Midweight Base Layer Crew - Women's Best Synthetic Bang for Your Buck	$55
	72	Smartwool Classic All-Season Merino - Women's Best Value for Merino	$90
	72	Patagonia Capilene Midweight Crew - Women's	$89
	71	Icebreaker 260 Tech Long-Sleeve Half-Zip - Women's	$135
	67	Smartwool Classic Thermal Merino 1/4 Zip - Women's	$120
	66	Kari Traa Rose Light Half Zip	$120
	65	Merino.tech 250 Crew - Women's Best Merino on a Tight Budget	$60
	64	Carhartt Base Force Midweight 1/4 Zip - Women's	$55
	63	REI Co-op Merino 185 Top - Women's	$80
	62	Roman Trail Outfitters Merino Long Sleeve - Women's	$60
	62	Ortovox 185 Rock'N'Wool Long-Sleeve - Women's	$110
	48	Hanes Cool Dri Performance - Women's	$19
	45	DEVOPS Thermal Compression Turtle - Women's	$27

Why Trust GearLab

When making our selection, we take hours researching the best options on the market before selecting the very best and subjecting them to our rigorous side-by-side testing plan. We wear them everywhere we go and have tested them across the world, from the high glaciers of Alaska to the rainy and cool landscapes of Iceland. The base layer tops we test are used for a minimum of three months, and we continue to test them until they see an update throughout the year. We take these tops trail running, backpacking, rafting, climbing, split boarding, and hiking to determine how each performs during unique experiences in the backcountry. Once we complete our field testing, we evaluate the durability of each layer, noting any tears or snags. Finally, we score across the same metrics to offer a comparative assessment based on our experience.

Our women's base layer testing is divided across six rating metrics:

• Warmth (25% of total score weighting)

• Breathability (20% weighting)

• Comfort and Fit (20% weighting)

• Durability (15% weighting)

• Drying Speed (10% weighting)

• Layering Ability (10% weighting)

Our testing team is led by Trish Matheny and Amber King. After spending over a decade in the Tetons, Trish knows what she wants in base layer performance. An avid rock climber, trail runner, and splitboarder, she wears base layers frequently while exploring the Sierra Nevada Mountains and beyond. As a seasoned gear reviewer, Amber spends her time backpacking into remote places, canyoneering through slot canyons, and finding cool trails to run worldwide. Women she meets along her adventures become additional testers to provide unbiased, diverse, and genuine feedback on all the base layer tops she tests.

Analysis and Test Results

A base layer top is an integral part of any women's outdoor wardrobe. This piece sits closest to the skin, wicks away moisture, and ultimately keeps you warm and comfortable while tackling summits or lounging around the chalet. The base layer tops we chose are composed of either synthetic materials, Merino wool, or a blend. No tops in this review contain cotton. Throughout testing, we rate each product using five key metrics: warmth, breathability, comfort and fit, layering ability, and durability.

What's the Best Value?

Wondering which tops offer the best performance relative to their price? We understand the importance of the return on your investment. Typically, the largest trade-off in this category lies in the materials used. Merino wool tends to cost more money than synthetic fabrics, and this higher price is passed on to the consumer. The Roman Trail Outfitters Merino Long Sleeve retails for less than half of our top performers. However, its thin materials stretch out over time, and you end up sacrificing durability. Similarly, the Merino.tech 250 Crew provides noticeably more warmth and increased durability due to its midweight construction but less wicking performance and softness next to the skin. And while options like the Hanes Cool Dri Performance and DEVOPS Thermal Compression Turtle are available for incredibly affordable prices, they simply do not measure up when it comes to quality and performance. Both layers feature designs that lack attention to detail when it comes to the thickness of their seams under the arms, which ultimately causes chafing and discomfort after long backcountry tours or multi-pitch rock climbs. They also caused us concern when it comes to durability, as we noted the stitching started to unravel in both layers after minimal use.

A couple of our favorite value-based purchases of all the garments that we've tested are the Ridge Merino Aspect Midweight and the REI Midweight Base Layer Crew. The Ridge Merino is on point with some of our top-performing base layers, while the REI Midweight offers incredible value in exchange for sufficient synthetic performance. However, it's also worth considering the long-term value of synthetic tops like the Arc'teryx Rho Hoody. Its superior craftsmanship and high quality make it one of our top choices season after season of use, which reduces its total cost over time. Want the best of both worlds? Consider the Merino wool that is combined with core-spun nylon found in the Smartwool Classic All-Season and the Black Diamond Solution Hoody. These options offer the comfort of Merino wool with the added strength and durability of synthetics like nylon and polyester for long-lasting performance and an increase in overall value.

Warmth

How many times have you broken a sweat while hiking uphill, only to start shivering once you slow your pace? The base layer tops that offer the highest level of warmth are those that can properly regulate body temperature no matter the activity, whether you're riding the chairlift or Nordic skiing. Different tops offer different fabric weights, which contributes to overall warmth. In general, if you know you will be sitting around in cold weather, choose a thicker option. If you think you're going to be moving a lot more with minimal breaks, choose a thinner option to avoid overheating. A midweight base layer is typically a good compromise.

When comparing fabrics, Merino wool stands out — it offers more insulating warmth and breathability, which equates to better thermoregulation overall. For example, the Smartwool Classic Thermal Merino 1/4 Zip and the Icebreaker 260 Tech Long-Sleeve Half-Zip are among the warmest and most insulating base layers in this review, packing in 250-260 g/m² of Merino wool. The Icebreaker Merino 200 Oasis Crewe is similar, with 200 g/m², making it a little less warm but not as thick. At 250 g/m², the Merino.tech Crew is thicker than the Oasis but receives the same score in terms of overall warmth due to the longer drying time. The slower drying speed while on the body makes this bargain layer more suited to layering during sedentary or low-output winter activities where you won't be working up a sweat. Not far behind the Merino.tech are two of our favorite blended layers, the Ridge Convict and the Black Diamond Solution 150. Both of these layers combine the strength and durability of synthetics with the warmth and odor-resistant qualities of Merino wool. While each layer improves upon warmth by adding a hood and thumb loops, the Convict effectively traps more body heat in its thicker 170 g/m² Merino wool interior.

Tops like the Ortovox 185 Rock'N'Wool (185 g/m²) and the Carhartt Base Force Midweight still receive high scores but offer just a little less warmth. Both options supply excellent thermoregulation on high-output days like cross-country skiing or trail running. Both of these options are warmer tops than the Smartwool Classic All-Season, which has a thinner construction and open neckline. This Smartwool's design is far more breathable and perfect to wear underneath warmer cold-weather items, but it is not built for stand-alone warmth during winter.

Most of the polyester tops we've tested don't offer the same “sit-around” warmth as Merino wool. Many are constructed with hollow polyester fibers. When it's cold in the morning, and you pull the top on, it won't feel as cozy as Merino wool simply because all the cold air is locked inside the fibers. However, once you get your body in motion, the layer will conceal the heat generated during your activity. When moving from warm to cold, tops like the Patagonia Capilene Midweight Crew and Arc'teryx Rho Hoody will typically adapt to their environment more readily than Merino wool. Of them all, the Arc'teryx Rho is our favorite synthetic because of the built-in fleece liner that keeps the skin warm and cozy even after you stop moving. The latest iteration of this layer features a versatile design that offers a neck warmer, hoody, and a full-face balaclava to protect you from inclement weather and radiant sun exposure in the alpine.

Breathability

This is the yang to warmth's yin. Without great breathability, you will not have much warmth during your cold-weather adventures. A key metric for thermoregulation, breathability defines how well the fabric allows heat to escape and how well it vents. When worn in a layered system, breathability enables fabrics to move moisture from the skin and through the fabric to the next layer, keeping your skin dry.

Surprisingly, the Patagonia Capilene Thermal Weight Zip-Neck lands at the top of this metric. Our testers were blown away by the wicking capabilities and fast drying speed of this impressive layer. Though not what we would typically consider a traditional thermal weight, due to its super lightweight and see-through design, the magic is in the breathability that optimizes warmth thanks to a micro-grid fleece interior and releasing sweat through the air permeable polyester fabric. The Ridge Convict features a very similar open grid pattern to the Capilene Thermal Weight but with a much thicker, midweight construction.

Another top that stands out in this metric is the Roman Trail Outfitters Merino. This model is quite warm for its lightweight design, provides excellent thermoregulation through a wide range of temperatures, and also vents well, thanks to its loosely woven fabrics. This is a great layer to consider during the summer months when you're headed high into the alpine, but we recommend leaving it at home during the colder months of winter. That said, the Roman Trail Outfitters top also works well as the base of a nicely layered system, whether beneath a midweight fleece or puffy jacket.

Essentially, the layers that excel at proper ventilation are those constructed from thinner materials and a fabric knit that isn't too tight for moisture to escape. The Smartwool Intraknit Thermal Merino is quite notable here. The stylish and strategically engineered ventilation panels throughout the design work to increase airflow and enhance breathability by featuring a tighter weave with a touch of elastane. The elastane helps to provide enough stretch to move with you during various activities. This midweight layer kept us warm enough during multi-pitch rock climbs in the fall while also dumping enough heat to get after it on long trail runs during the shoulder seasons. Smartwool's Classic Thermal 1/4 Zip is an interesting comparison product, as it scored lower for breathability even while it stood out for its exceptional warmth. We attribute its lackluster performance in this metric, at least partially, to overall fit as we found the cut runs small. Sizing up could ensure a bit more balance between the two.

The 100% synthetic construction of the Patagonia Capilene Midweight Crew is also quite breathable. Its diamond-grid architecture promotes great airflow with a face fabric that cuts the wind when worn independently. And the polyester construction of the lightweight and highly breathable Hanes Cool Dri Performance was perfect for those warm days in the desert when you're searching for shade.

When spending long days rock climbing, our testers loved how well the Black Diamond Solution 150 Merino was able to keep us cool in the sun as well as warm in the shade. This layer features increased breathability through its Nuyarn Merino wool stretch technology and is a joy to wear.

Comfort and Fit

When testing for this metric, we assess each top to determine which fabric has the coziest and most versatile fit. This is perhaps the easiest metric to test for; all we have to do is record our notes while we hang around the campfire or enjoy a rest day. We also evaluate how the fabrics feel next to our skin after several days of wear without washing so we can determine whether or not the feel of the fabric changes over time. In general, we love Merino wool tops with a fitted, stretchy design simply because they offer the maximum level of comfort.

After a few washes and some time on the trails, The Black Diamond Solution 150 Hoody became one of the most comfortable base layers in this review. The Solution features 78% Nuyarn Merino wool and 22% polyester to maintain strength and durability, with a bit of stretch, as well as flatlock hemlines. The Arc'teryx Rho Hoody is also notable thanks to its cozy, fleece-lined polyester and elastane material. We love that the latest iteration features a neck warmer, a hood with a small opening for a ponytail, and a balaclava for maximum cold-weather protection. The fit has changed dramatically from previous iterations — Arc'teryx scrapped the boxy fit and kangaroo pockets for a trim-fitting base layer meant to remain close to the body to minimize any unnecessary bulk. This trim fit also enhances the layer's ability to trap body heat generated during activity due to the lack of draft.

The Ridge Convict is another great consideration for a comfortable, well-fitting layer. The flattering fit and feminine style of this top is true to size and super cozy next to the skin, thanks to its ultra-fine Merino wool interior.

The Ortovox Rock'N'Wool is one of the softest wool options that we tested, featuring a lighter construction and 100% Merino wool sourced from Tasmania; we loved how soft the wool felt next to our skin. However, we were disappointed that the latest version of this shirt is designed with bulkier flatlock seams across both forearms. We found these seams to be distracting and uncomfortable, in addition to bunching beneath layers worn over the top. We hope future versions ditch the seemingly unnecessary thick seams and improve their placement because the wool used itself is awesome.

Other super soft Merino wool options that stood out amongst the competition are the Ridge Merino Aspect Midweight and the Smartwool Classic All-Season. They both feature a slim fit with a very basic crew construction that utilizes strategically placed flatlock seams to reduce bulk and prevent chafing while carrying a heavy pack. Our testers love the long cut and slim fit that effectively trapped our body heat on both crews. However, the Aspect offers a thicker Merino wool that's combined with discreet yet functional thumb loops for added warmth and structure to the overall design, details that our testers especially appreciated once the temperatures dropped. Similar to the Aspect is the Mons Royale Cascade Merino Flex Mock Neck LS. This top offers a very flattering slim fit that features a looser-fitting mock neck for additional warmth. The layer offers a short torso length that layers well with high-waisted bottoms and thumb loops to improve ease of layering.

When evaluating the fit of each base layer, we handed these shirts to a group of women who varied in height, weight, and body shape to offer the most objective recommendations possible. Some were tall, while others were short; some had lots of curves, while others had none. In our evaluations, tops with a stretchier and more voluminous fit proved to be the most versatile. We also looked at the relative lengths of the arms and torso to see which provided the best overall coverage. Our lead tester (5'6", 130 lbs) prefers size small in most of these tops but found the Kari Traa Rose Light Half Zip and the DEVOPS Thermal Compression Turtle to fit better in size Medium. Though the DEVOPS is a compression layer meant to offer a snug fit, we found the sleeve and torso lengths too short to allow for a full range of motion.

Durability

The best base layers out there should last for you to receive the greatest return on your investment. A proper base layer shouldn't shrink, stretch out, pill, or fall apart after just a few months of use. Most importantly, a durable top shouldn't easily succumb to snags and tears after just a few times out on the trail. During our testing period, we shimmied through canyons and bushwhacked through forests to see if the fabric snagged or tore. We also wore each layer with a loaded backpack. After all of this, we inspected each product to evaluate the craftsmanship. In addition, we test each base layer continuously throughout the year and will update this section with our most current recommendations.

It's been many years since we first started testing the Arc'teryx Rho Hoody, and previous versions are still going strong. We have used and abused it while climbing, hiking, split boarding, trail running, and canyoneering. After many long years of use, there are still no significant areas of wear and tear, and we expect the same to be true of the most current version. The high-quality design features a combination of Merrow and flatlock stitched seams that effectively hold the trim-fitting layer in place without limiting the wearer's range of motion. Our only caveat is that the fabric retains a little smell. Aside from that, it has truly withstood the test of time and continues to exceed our expectations.

The Patagonia Capilene Midweight is a true workhorse. The synthetic fibers are strong and retain their shape, even after being put through the wringer. The Midweight stands apart from other Patagonia options in this review due to the tighter weave of the diamond grid pattern. We question the longevity of the Capilene Thermal Weight — not for lack of quality, but simply due to its thinner, more air permeable, see-through design that optimizes breathability. Our only complaint about this layer is that the thumb loops lack the same quality as the rest of the layers — they are thin and don't inspire long-lasting confidence. Rounding out our synthetic durability favorites is the REI Co-op Midweight featuring reinforced flatlock seams as well as thicker, more comfortable thumb loops.

Merino wool contenders are less durable than synthetic options, but they don't hold onto odor. Of these, the Kari Traa Rose Half Zip is the most durable. It has a tightly knit face fabric that doesn't easily snag. The nylon fibers are shorter and have proven to be more durable and a better option for those needing a top for high-friction sports like canyoneering, bushwhacking, or rock climbing. We'd also like to highlight the Nuyarn stretch Merino wool found in the Black Diamond Solution 150 that impressed us during our winter testing period when we snagged our sleeves on a tree. After ripping a hole in the material, it didn't continue running throughout the length of the fabric like other more delicate Merino wool contenders in this review. The hole has remained small, allowing for continued use. And not to be overlooked, the Ridge Convict features a durable polyester exterior that effectively protects the ultra-fine Merino wool interior.

Layers like the Hanes Cool Dri Performance and the DEVOPS Thermal Compression Turtle did not impress our testing team when it came to durability, as we noted the stitching on both layers started to unravel and showed signs of wear after very minimal use. While the light color options of the Hanes Cool Dri Performance may make this lightweight layer a perfect choice for sun protection rather than an extra layer of warmth against the cold, we did note the light colors easily stained after minimal use.

Drying Speed

When selecting a base layer for your next outdoor adventure, drying speed could truly make or break the decision. It's important that the layer sheds moisture generated during activity while also drying quickly on the body when exposed to fresh air.

We immediately noticed a trend when we started recording drying speeds for each base layer. The synthetic or Merino wool and polyester blended layers offered the fastest drying speeds, much faster than their 100% Merino wool equivalents. We approached these tests from several different angles, including drying on a line, drying on the body, and drying overnight. Now, we can confidently report back on our top performers.

At only 37 minutes on the line and 25 minutes on the body, the Patagonia Capilene Thermal Weight Zip-Neck was the fastest to dry. Unsurprisingly, this base layer boasts great breathability due to the porous fabric that allows air to flow through and wick moisture away from the skin.

The Ridge Convict had a drying speed of 40 minutes on the line and only 10 minutes on the body, and the Arc'teryx Rho Hoody dried in 40 minutes on the line and 25 minutes on the body. The open grid pattern truly harnesses the wicking capability of its synthetic exterior while simultaneously allowing air to permeate the layer and offer a speedy drying time. Other impressive layers in this metric are the Smartwool Classic All Season, which dried in only 43 minutes thanks to its super lightweight construction, the Ridge Merino Aspect Midweight, and the Patagonia Capilene Midweight Crew with slightly longer drying speeds at 49 minutes on the line and between 30-35 minutes on the body.

Layering Ability

A good base layer should be versatile and easy to use within a layering system. While most long-underwear tops are presumably that “next-to-skin” layer, it is a bonus when you can wear a tank or tee beneath when conditions are expected to warm up. Not only that, but you want to ensure that you can throw layers on top and remove them without too much effort. Here, we evaluate the knit of the fabric and spend time trying on each one with different layers over the top. Base layers that perform best in this category feature slippery face fabrics, a thinner construction, and thumb loops.

Synthetic layers traditionally have more rigid fibers that, in combination, make for easy layering. The Rho Hoody is one of the easier options to layer thanks to its frictionless face fabric that slides smoothly against even the fleeciest of mid-layers. The latest iteration features a much trimmer fit and minimal design that also improves layering by reducing bulk, especially in the hood, which features a small opening for a ponytail. The Black Diamond Solution 150 Merino features a streamlined design complete with thumbholes that help increase the ease of layering, as they hold the layer in place while putting on gloves or a midweight layer over the top.

The Patagonia Capilene Midweight and the Patagonia Capilene Thermal Weight Zip-Neck are both great layering options with built-in thumb loops that keep the arms in place, while the REI Co-op Midweight features a frictionless face fabric, in addition to a super stretchy design that hugs the body. All are great options in this category. The Hanes Cool Dri Performance is also a synthetic option that is true to size and easy to layer. Our testers loved climbing in this top, which features enough length to easily pull below our climbing harness and over our crack gloves. The DevOps Thermal Compression Turtle also features a super slim-fitting compression design that hugs the contours of the body and a smooth interface that is easy to layer over the top, but since it runs small and offers less breathability, it didn't perform as comfortably for similar uses.

Of the Merino wool competitors, thinner options like the Roman Trail Outfitters, Smartwool Classic All-Season, and Ridge Merino Aspect are much easier to layer than thicker options. Layers like the Kari Traa Rose and the Smartwool Intraknit Thermal work well, too, because of how fitted they are, making sliding layers over them easy.

How to Choose Base Layers for Women

A high-quality base layer can make or break the comfort of your outdoor activities. It's got a big job: keep moisture moving away from your skin while offering enough warmth, comfort, and mobility to allow you to focus on your activities without giving the garment a second thought. When getting outfitted for your day, this is the layer that will sit against your skin. Sometimes, it will be worn on its own. This is when style points may rank higher as a priority. But where it really shines is when temperatures drop. At that point, it will find a home underneath a fleece or other mid-layer and, if conditions require it, inside yet another jacket or with a shell on top. Base layer tops are meant to be part of a system, facilitating thermoregulation based on whatever varied activities and weather conditions lie ahead. If all this technical layering is new to you, check out our helpful article on how to layer clothing for each season and how to layer in general. Below are a few key considerations our team has identified as important to review before you get started on your next purchase.

How Much Do You Need to Spend?

This is the age-old question: is more really better? And, like with many things, there is no single, simple answer. Merino products tend to come at a higher cost, as do tops that come with more features and/or enhanced performance elements. The least expensive options are generally going to be fully synthetic and lack some of the key design characteristics outdoor enthusiasts prioritize. That said, top-performing synthetic options sell at a premium price on par with the best Merino blends, and there are a number of reasonably priced models of all fabric types that sit somewhere in the middle. In this case, you may get more performance potential in a garment by spending more, but not everyone needs that much. In many cases, a lower-cost base layer can meet your needs just fine, so be sure you've got a clear idea of what your real use plans are before adding new items to your cart.

Which Fabric Type is Best?

Base layers tend to come constructed out of a few select fabric types, including Merino wool, various synthetics (polyester, nylon, spandex, and such), cotton, or a mixed blend of the same. Some other natural fibers, like bamboo, Tencel, alpaca wool, and hemp, are now finding space in the market as well. Generally speaking, super soft Merino wool is considered the top choice for garments of this type, thanks to its naturally wicking, antimicrobial “ultrafine” fibers that can provide superb warmth in wet and dry conditions and effectively resist body odor, even with significant use between washes. This combination makes it perfect for base layer tops and long underwear. Among its few limitations are a lack of durability, slow drying times, and steep price tags. Few other materials, natural or otherwise, can compete.

In contrast, synthetics tend to be remarkably durable and can come in any number of material combinations to address specific performance preferences and construction needs. Fabrics like recycled polyester, torrent, nylon, spandex, and elastane are often combined to deliver targeted results, including impressive stretch and breathability, as well as powerful wicking and quick-dry features. Rarely will these fabrics be able to match the warmth of wool, and they generally hold odor far more readily than natural fibers. But, overall, they can perform admirably well and are sold at a far lower price than many Merino products. Merino-synthetic blends have also now become common, with each unique combination attempting to merge the best of both worlds to achieve the perfect, high-quality, durable base layer, and there have been some exceptional results.

Cotton base layers are out there, but we suggest avoiding them unless you are just lounging around at home. Cotton holds onto moisture and acts as a cooling agent when wet. This makes it a terrible choice for anyone planning to use their layer for sweat-producing activities or in need of a performance layer to help regulate body temperature and provide warmth in colder conditions.

What do the Different Fabric Weight Mean?

Base Layers come in three primary fabric weight options: lightweight, midweight, and heavyweight. As the name implies, lightweight layers are perfect for warm weather conditions. They can also serve as a stand-alone top on warmer days or as a reliable bottom layer against the skin during the winter months. What's nice with these is that thicker layers slide easily over top for additional warmth. Midweight construction tops are perhaps the most versatile, providing extra warmth when worn independently, and also useful as moisture-wicking bottom layers under a heavier jacket or fleece. Midweight layers are our testing team's first choice when it comes to off-season runs and skinning uphill to earn turns in the backcountry. Heavyweight layers are more specific to those who live or play in very cold climates and offer the least amount of versatility of the lot.

What Fit and Features Matter?

While you can opt for a looser fit or size up, base layers are generally intended to sit close to the skin. The goal is neither too tight nor too baggy, with arms and torso cut long enough to maintain full coverage as you lift your arms and move your body. Such a fit enables effective wicking and maintains warmth. Various cuts, material combinations, and features give you options in style, ventilation, and added performance benefits. Things like crew cuts, zip necks, thumb loops, pockets, UPF protection, and hoods all serve different needs and can be great additions but may not be required by every shopper. Often, it comes down to preference, and it all depends on the intended use. For deeper insights on how to decipher your needs before you buy, take a look at our comprehensive buying advice for women.

Conclusion

The clothing layer next to your skin is integral for keeping you warm and comfortable while exploring the great outdoors. Whether you're snuggling up next to the fire or shredding down a double black diamond on the ski hill, aim for one that performs to meet your individual needs. We've done the hard work and tested some of the best options available. We hope our recommendations help you select the best base layer for your next backcountry adventure.