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We put 22 of the top women's base layers to the test to find the warmest and most versatile options to carry you comfortably from the slopes to a night by the fire.
Credit: Trish Matheny
By Trish Matheny ⋅ Review Editor ⋅ Updated April 1, 2026
When temps drop, your first thought might be that you need to get a warmer jacket, but one of the easiest ways to boost the warmth of your winter kit is to simply add a great base layer. The best ones keep you warm and cozy while still letting your skin breathe.
The overall best base layer we tested is the Icebreaker Merino 200 Oasis Crewe. This 100% Merino wool top is super soft on the skin, has a great fit, and the low-profile crew neck makes it easy to layer under anything from a fleece to a sweater to a puffy.
For the budget-conscious shopper looking for a good value, check out the REI Co-op Midweight Base Layer Crew. The soft, stretchy fabric and durable construction will save you money compared to premium options.
We've purchased and tested dozens of the best base layers for women since 2015, and our current review features some of the most innovative options we've seen to date. From casual hangs around the campfire to adventures like sailing the high seas to scaling thousand-foot cliffs, skiing in the high mountains, and running ultra-distance miles, we put these layers through their paces to find the best.
Editor's Note: Our women's base layer review was updated on March 16, 2026, to include new models from Arc'teryx, Stio, and Ibex in addition to updated testing perspectives on current and previous award winners.
The Icebreaker Merino 200 Oasis Crewe features a high quality 100% Merino wool construction that feels so great against your skin that you'll wanna wear it every day. After testing several iterations of this design, our testers love the ultrafine and super soft fibers that are tightly woven to create a more durable and effective layer when it comes to containing body and heat and wicking moisture. “The layer moves with my body but maintains a snug fit and shape when worn for multiple days between washes,” says our lead tester. For such a simple design, it sure provides excellent performance as a complement to your cold-weather kit, as well as a standalone layer during the fall and spring months or when you're just waiting out a storm inside your home.
SPECIFICATIONS
Fabric Weight Class
Midweight
Material
100% Merino wool
Fit
Slim fit
Odor Control Fabric
Naturally odor resistant
Avaliable Cuts
Crew, 1/2 zip neck
One of our few complaints is the limited breathability when layered beneath outer layers. While the Oasis can efficiently wick moisture away from the skin, the fabric holds onto sweat unless it is exposed to airflow. If you want a layer that dries faster and offers better breathability, we love the Stio Trax Power Grid Half Zip Hoodie, which has a raised grid pattern that maximizes airflow. After several years of evaluating various base layer crews, we can confidently say that the Oasis is among the top performers in our testing fleet. And we think you'll love the soft and cozy 100% Merino wool construction so much that you'll wanna wear it every day. If you're interested in a more affordable version, we love the Smartwool Classic All-Season Merino, it's just not as thick and will not be quite as warm or durable.
Though the Icebreaker 200 Oasis Crewe doesn't perform as well as its air-permeable synthetic competitors, we did appreciate the thicker fabric during ski tours early in the spring. Credit: Trish Matheny
Thoughtful seams and soft Merino for next-to-skin comfort
Excellent for layering
Highly breathable
Fast drying speed
CONS
Thin Merino wool susceptible to durability issues
Lacks warmth as a stand-alone piece for year-round use
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 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. In addition, the combination of merrow stitch and flatlock seams prevents chafing when worn beneath a heavy backpack. Our lead tester stated, “I really appreciate the naturally odor-free Merino. It keeps the layer fresh, even when I wear it multiple times between washes.”
SPECIFICATIONS
Fabric Weight Class
Lightweight
Material
Merino jersey: 88% Merino wool, 12% nylon core
Fit
Regular fit
Odor Control Fabric
Naturally odor resistant
Avaliable Cuts
Crew
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. But if you plan to keep moving throughout winter, breathability and wicking are likely more essential considerations, and this Smartwool layer is perfect as the base for a cold-weather layering system or as a stand-alone piece during the cooler months.
The Classic All-Season is a Merino wool blended design that performs well at the base of other layers or as a stand alone piece during the warmer months of the year. Credit: Gus Landefeld
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.
SPECIFICATIONS
Fabric Weight Class
Midweight
Material
92% recycled polyester, 8% spandex
Fit
Regular fit
Odor Control Fabric
None
Avaliable Cuts
Crew, 1/2 zip neck
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. During testing, we noticed it held onto odor almost immediately when used. No synthetic options we've tested do a great job of avoiding this problem, but Merino and Merino-synthetic blends, like the Ridge Merino Convict, typically perform better overall. While the REI Midweight Crew's fabric successfully wicked moisture away from our skin, it couldn't release it as efficiently through the tightly woven fabric, so drying took longer. This sometimes meant sacrificing precious warmth during colder temps, which is not a trait you want when you're going hard. For this reason, we do not recommend the REI Midweight Crew for high-output activities or for the depths of winter. Nonetheless, 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.
the REI Midweight Crew features a soft and stretchy synthetic design along with functional and comfortable thumb loops to make for easy layering. Credit: Trish Matheny
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 top choice for high-intensity cold-weather sports or frequent use, it is constructed from a nice, thick 100% Merino wool that delivers welcomed additional warmth on cold days. The thicker fabric also increases the durability of this layer, making it noticeably more resistant to microholes and tears, though it is not quite as soft as other options. The relaxed fit is true to size and easy to layer over, making it an easy, low-cost choice for the occasional resort turn, a shoulder-season hike, or a relaxed winter day at home by the fire.
SPECIFICATIONS
Fabric Weight Class
Midweight
Material
100% Merino wool
Fit
True to size
Odor Control Fabric
Naturally odor resistant
Avaliable Cuts
Crew, 1/4 zip
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 if you try to pull up your sleeves. The thickness of this layer also requires a longer drying time, and is less breathable when you start to sweat. If you're willing to spend a few more bucks to get a shirt that will wear better, allow us to point you to the well-priced, high-performance Smartwool Classic All-Season Merino. It would make a great addition to any ski, board, or hiking kit, thanks to its top-notch wicking performance. However, for anyone who lives in warmer climates or is city-based and unlikely to wear this layer on a daily basis 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 heading out on your yearly ski trip.
Whether you're stoked to brave the elements outdoors or the cold temperatures and dark nights push you to train inside, the Merino.tech crew is a versatile and affordable layer that's perfect for year round use. Credit: Trish Matheny
Hood, neck warmer, and full-face balaclava for increased warmth
High quality
CONS
Lacks some breathability
Expensive
Holds more odor than Merino
We've tested several versions of the Arc'teryx Rho Hoody over many years, and can confidently say that it outperformed the competition on some of the hardest-hitting days on the mountain. This hoody is crafted for more technical endeavors, featuring a super slim fit in order to efficiently layer and maximize warmth and comfort. The fleece-lined interior feels cozy against the skin and does a great job of wicking sweat. This feature-rich design includes a unique balaclava-style hood complete with an opening for your ponytail to reduce bulk inside the hood. “If you have lots of curly hair like me, you'll appreciate the opening in the hood,” says our lead tester. 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. The high neckline features a softer lining for additional comfort and is also appreciated for added warmth and sun protection during alpine missions when you need to be prepared to experience all seasons. As is true with most synthetics, wear and tear is minimal, even after being put through the wringer. Tried, tested, and truly awesome.
SPECIFICATIONS
Fabric Weight Class
Lightweight
Material
Torrent 190 stretch fleece with Polygiene: 84% polyester/16% elastane
Fit
Slim fit
Odor Control Fabric
Polygiene treatment
Avaliable Cuts
Crew, hoody, zip neck
A common drawback of synthetic layers is that the fabric can often hold onto body odor, especially after we've worn it for multiple days in the backcountry. While the Rho Hoody is treated with a Polygiene antimicrobial treatment, we've noticed that it gradually wears off with heavy use. When it comes to durability, the only issue we've experienced over the years is that the marrow-stitched seams tend to fuzz when they come into contact with velcro in the wash or on your ski bibs. This is more of a cosmetic issue than a durability flaw, but still worth mentioning. It is also not as breathable as some other tops. It is a much thicker (and warmer) design than other lightweight Merino wool options in the lineup. That said, this makes it a better standalone layer in shoulder seasons and is also great for long, stationary rides on the chairlift. You might have noticed that the Rho Hoody is pricier 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 you get from it is definitely worth the investment. The Rho Hoody is best for someone seeking a versatile, durable, technical layer that looks great to boot.
The Stio Trax Power Grid Half Zip Hoodie is the perfect layer for women who like to push the pace thanks to an exceptional balance of warmth and breathability. The Polartec Power Grid synthetic-blend fabric feels great next to your skin, while the micro-grid pattern provides excellent wicking performance. It features a regular fit that's true to size and includes warmth-enhancing features such as a hood, a zip neck, and thumb loops for additional coverage when the temperatures plummet. Whether doing laps on the skin track, out for a trail run, or on a multi-pitch rock climbing adventure, our lead tester appreciated the breathability and moisture-wicking capabilities that allowed her to stay dry and comfortable in pretty much every condition.
SPECIFICATIONS
Fabric Weight Class
Lightweight
Material
Polartec® Power Grid™ Fleece, 91% Polyester, 9% Spandex, 119 g/m2, Wicking and Anti-Odor Finish
Fit
True to size
Odor Control Fabric
Wicking and Anti-Odor Finish
Avaliable Cuts
Crew, Hoody
We found it difficult to layer the Trax Power Grid with merino wool, as the two fabrics would often grab each other, causing bunching. The thumb loops made it slightly easier, but in general, we preferred to layer this with slippery synthetic shirts underneath and ski bibs or jackets over top. We didn't experience any snags or tears in the lightweight fabric during testing, but we don't anticipate this layer lasting as long as other synthetics, simply because of the ultralight, see-through sections of fabric between the grid patterns. As for now, the anti-odor treatment in the fabric is holding strong without retaining odors from our adventures, although merino layers like the Ibex Woolies will serve you better thanks to its naturally odor-reducing properties. And while this layer is perfect for active outdoor pursuits for women on the go, its lightweight, air-permeable construction doesn't provide the best sedentary warmth for riding the chairlift or walking the dog during the coldest month of the year. That said, if you need a layer to keep up with you no matter the activity, the Stio Trax Power Grid Half Zip Hoodie is our new go-to thermoregulating design that traps body heat when you need it and releases it when you don't.
Our testers worked hard to remove snow after a classic High Sierra Atmospheric River but stayed comfortable thanks to the excellent thermoregulation provided by the Stio Trax Power Grid Half Zip Hoodie. Credit: Trish Matheny
The Ibex Woolies Pro Tech Crew is an excellent lightweight base layer that our testers loved to wear as a stand-alone layer when the weather is cool (but not cold) and as the base of our kit when the temperatures plummet. The super-soft, cozy fabric is a blend of 85% Merino wool and 15% nylon, which gives it a little stretch and helps maintain its structure. The real magic of this layer lies in the Nuyarn technology, which increases performance and durability. “The internet suggested that I size up, but I'm glad I didn't, especially since the layer stretches a little bit after heavy use,” said our lead tester. She appreciated the slim fit and thought the longer sleeves and torso trapped more body heat. When worn as a standalone layer during early-spring rock climbs and training runs, the Pro Tech Crew kept us warm and comfortable, and we were impressed by its breathability and wicking performance. Another bonus to a lightweight base layer is the fast drying speed, should you work up a sweat in the backcountry and need it to dry quickly before your next lap.
SPECIFICATIONS
Fabric Weight Class
Lightweight
Material
85% Merino Wool, 15% Nylon
Fit
Slim fit
Odor Control Fabric
Naturally odor resistant
Avaliable Cuts
Crew, Half Zip
One major drawback to the Pro Tech Crew is the price tag, which is a small investment, especially given its lighter weight. If you are on a tighter budget and looking for something similar, we suggest checking out the Smartwool Classic All-Season Merino. As for the Pro Tech, not all women will appreciate the slim fit or the ultralight fabric, which tends to be a little see-through, especially in the lighter color options. And finally, this layer isn't for ladies looking for standalone warmth during the coldest months of the year. While we love it on its own during most of the year, think spring trail runs, fall rock climbs, or lounging around indoors, we definitely want to layer it beneath some other insulate layers when the temperatures truly drop. That said, the thin fabric and crewneck cut make it easy to layer. If you do want a heavier option, we recommend the Stio Basis PeakWool Midweight Half Zip as a much thicker and cozy option.
The ultralight Ibex Woolies Pro Tech Crew dries quickly thanks to its super thin construction that's great on its own during cooler weather or layered at the base of your outer and mid layers. Credit: Trish Matheny
Product Comparison Table
Base layers are an important part of any backcountry mountain objective; we were impressed with the performance of the Oasis Crewe while riding Solar Bowl. Credit: Steve Mace
How We Tested
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 to the climbing crags of southern Spain. 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 for trail running, backpacking, rafting, climbing, splitboarding, and hiking to see how each performs in unique backcountry conditions. Once we complete our field testing, we evaluate each layer's durability, noting any tears or snags. Finally, we score across the same metrics to offer a comparative assessment based on our experience.
Our team carefully tested these layers during a variety of activities to assess everything from warmth to drying speed to durability and more.
Our women's base layer testing is divided across six rating metrics:
Our testing team is led by Trish Matheny and Amber King. After spending over a decade in the Tetons and living outdoors for several seasons as a member of the Yosemite Search and Rescue Team, Trish knows what she wants in base layer performance. An avid rock climber, trail runner, and splitboarder, Trish wears base layers frequently while exploring the Eastern Sierra Nevada Mountains, Yosemite Valley, Spain, Chile, Mexico, 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.
We put these layers through the wringer in order to determine those that feature the very best performance. Credit: Trish Matheny
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, and it's most critical job is to wick away moisture, ultimately keeping 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.
Worse Value
Better Value
What's the Best Value?
Wondering which tops offer the best performance relative to their price? One of our favorite value-based purchases of all the garments that we've tested is the REI Midweight Base Layer Crew. It offers incredible value in exchange for sufficient synthetic performance. Very often, synthetic tops are more affordable than wool, but there are some exceptions. The Merino.tech 250 Crew is a 100% wool option that provides noticeably more warmth and increased durability due to its midweight construction, but offers lower wicking performance and less softness next to the skin. However, it is a great buy for those who only need a base layer now and then.
Though it's not a high-tech performance layer, the Merino.tech is a warm, functional, and affordable wool base for those who don't want to spend $100+ dollars on a top. Credit: Gus Landefeld
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 keep you warm are those that can properly regulate body temperature throughout the day, whether you're riding the chairlift or Nordic skiing. Different tops offer different fabric weights, which contribute 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.
Choose a Weight Appropriate to the Activity
Choose lightweight fabric for any of the tops we reviewed if you want something that'll breathe easier. Short sleeve options are also available sometimes, along with zip necks, both of which offer more ventilation. If you run hot, lightweight fabric is the way to go, but if you get cold easily, opt for mid-heavyweight construction. During our testing, we reviewed many lightweight and midweight models but only one heavyweight model. However, most of the layers listed here have different weight options available, so if you like the way a top sounds, but feel like you need a bit more warmth, check for other fabric weights.
When comparing fabrics, Merino wool is usually the go to for base layers. It offers greater insulating warmth and breathability, which equates to better overall thermoregulation. For example, the Stio Basis PeakWool Midweight Half Zip, 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 for the Icebreaker and Smartwool models, and a whopping 280g/m² for the Stio. Of the three thickest layers, the Icebreaker has the highest neckline, while the Stio features the best fit and softest fabric next to skin.
The Stio Basis PeakWool Midweight Half Zip features one of the thickest midweight constructions that we've tested and includes a longer torso and sleeves along with thumb loops for additional warmth. Credit: Trish Matheny
The Icebreaker Merino 200 Oasis Crewe is similar, with 200 g/m², making it a little less warm but not as bulky under your jacket. At 250 g/m², the Merino.tech Crew is thicker than the Oasis but receives the same score in terms of overall warmth because it doesn't wick as well. This makes it a bargain layer more suited to layering during sedentary or low-output winter activities, when you won't be working up a sweat.
We found layers like the Icebreaker 200 Oasis to offer excellent thermoregulation, both trapping body heat and also releasing moisture through the fabric. And the Merino.tech 250 Crew is a great option for those seeking midweight warmth on a tighter budget.
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 Ibex Woolies Pro Tech Crew and the Smartwool Classic All-Season, which have thinner constructions along with open necklines. They are perfect stand-alone designs for fall temperatures, and their slim-fitting, minimalist designs also layer nicely below your outer layers during the winter.
While lightweight options like the Smartwool Classic All-Season and Ibex Woolies Pro Tech Crew feature open necklines instead of zippered necklines or balaclava, they can be perfect for the change of season.
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. That is unless, you select the Arc'teryx Rho Hoody that features a brushed fleece interior. The layer also features a versatile balaclava-style hood that can cover the face and head in order to contain body heat when it counts.
The Arc'teryx Rho Hoody features a unique set of features designed to maximize warmth within the lightweight construction. Credit: Trish Matheny
Once you get your body in motion, these synthetic layers will retain the heat generated during your activity. When moving from warm to cold, tops like the Patagonia Capilene Midweight Crew will typically adapt to their environment more readily than Merino wool. The Stio Trax Power Grid Half Zip Hoodie is a similar synthetic option that is great for bodies in motion, as the Polartec fleece and raised grid pattern allow the layer to effectively wick sweat while retaining body heat. The hood, zip neck, and thumb loops provide additional coverage, increasing the warmth of the lightweight design. While this isn't a great option for standalone warmth during the coldest months of the year, we love it for high-output activities, because you'll stay warmer if you're dry.
The Stio Trax Power Grid Half Zip Hoodie isn't our first choice for stand alone warmth in the winter, however, it does feature a high neck line, thumb loops, and hood to contain body heat within the highly breathable design. Credit: Trish Matheny
Breathability
This is the yang to warmth's yin. If you're wearing a sweat-soaked top, you will not stay warm for long 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 moisture to move from the skin through the fabric to the next layer, keeping your skin dry.
The Patagonia Capilene Thermal Weight Zip-Neck features ample breathability thanks to the lofted synthetic design that allows lots of airflow, making it perfect for high output activities. Credit: Trish Matheny
Layers like the Stio Trax Power Grid Half Zip Hoodie and the Patagonia Capilene Thermal Weight Zip-Neck land at the top of this metric due to their thoughtfully designed synthetic constructions that maximize airflow through raised grid patterning, which allows the layers to wick sweat and release it through their somewhat see-through construction. Although these are not what we would typically consider traditional, thick, and bulky thermal layers, their super lightweight, somewhat see-through designs make the magic in their breathability, which optimizes warmth thanks to a micro-grid fleece interior and releases sweat through the air-permeable polyester fabric. If you're having a hard time deciding between the two, we recommend the Stio Trax Power for its superior fit and durability, as well as its versatile hood and comfortable thumb loops.
The grid patterning of the Stio Trax Power Grid Half Zip Hoodie make it easier for air to permeate the design to increase wicking performance and breathability. Credit: Trish Matheny
Other top performers are the Ibex Woolies Pro Tech Crew and the Roman Trail Outfitters Merino. These models are quite warm for their ultra-lightweight design, and they provide excellent thermoregulation through a wide range of temperatures. These are great base layers to consider during the summer months when you're headed high into the alpine, and they work well as the base of a nicely layered system in the winter too, whether beneath a midweight fleece or puffy jacket.
Ultralight designs like the Ibex and the Roman Trail make great choices for thermoregulation in cooler temperatures.
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, strategically engineered ventilation panels throughout the design increase airflow and enhance breathability through 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.
Not only does the innovative design of the Smartwool Intraknite Merino 200 look cool, it also offers strategically placed ventilation panels to allow the layer to breathe and release moisture. Credit: Steve Mace
Comfort and Fit
We assess each top to determine which fabric offers the coziest, most versatile fit. We 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 their feel changes over time. In general, we love Merino wool tops with a touch of nylon or spandex simply because they offer the maximum level of comfort.
The Arc'teryx Rho Hoody is also notable for its cozy, fleece-lined polyester and elastane. We love that the latest iteration features a neck warmer, a hood with a small ponytail opening, 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 slim-fitting base layer that stays close to the body, minimizing unnecessary bulk. This trim fit also enhances the layer's ability to trap body heat generated during activity by cutting out drafts.
The articulated patterning and gusseted underarms create a full range of motion for ladies who select the Arc'teryx Rho as the base layer fit for their next adventure. Credit: Trish Matheny
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 features bulkier flatlock seams across both forearms. We found these seams to be distracting and uncomfortable, and they bunch 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.
We like the next-to-sin feel of the Ortovox Rock'n'Wool's fabric, but we are unimpressed with the location and thickness of the seams on the forearm and chest. Credit: Toby Swimmer
Other super soft Merino wool options that stood out amongst the competition are the Ridge Merino Aspect Midweight, Ibex Woolies Pro Tech Crew, and the Smartwool Classic All-Season. These crews feature slim fits with a very basic crew construction, utilizing strategically placed flatlock seams to reduce bulk and prevent chafing while layering or carrying a pack. Our testers love the longer torso and slim fit that effectively traps our body heat on each crew, though the Ibex features a higher neckline that gives it an extra edge. That said, 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.
The slim-fitting designs of the Ibex Woolies Pro Tech Crew. The Ridge Merino Aspect, and the Smartwool Classic All-Season sit close to your skin, effectively trapping body heat as well as offering flattering fits.
Similar to the Aspect is the Mons Royale Cascade Merino Flex Mock Neck LS. This top offers a very flattering slim fit and a looser mock neck for additional warmth. The layer offers a short torso length that layers well with high-waisted bottoms, and it features thumb loops to make pulling your arms through the next layer a bit easier.
Our lead tester really appreciated the slim-fitted design of the Mons Royale Cascade for a flattering fit that offers low bulk layering. Credit: Trish Matheny
When evaluating the fit of each base layer, we handed these shirts to a group of women with varying heights, weights, and body shapes 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, more voluminous fit proved 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 were too short to allow a full range of motion.
Though the DEVOPS Thermal Compression Turtle base layer is created for snug, compression-like fit, we found the torso and sleeve lengths to limit range of motion. Credit: Trish Matheny
Do Tall Options Exist?
Need a shirt with a long torso and arms? Luckily, we have a host of options. Of synthetic tops, the Arc'teryx Rho features a super stretchy fabric and a longer fit in the arms and torso. The Ibex Woolies Pro Tech Crew, Smartwool Intraknit Thermal, Icebreaker Merino 200 Oasis Crewe, and the Ridge Merino Aspect also feature stretchy constructions with plenty of length through the arms and extra fabric in the torso.
The Smartwool Intraknit has a slim, long fit, and is slightly longer in the back. Credit: Steve Mace
Durability
The best base layers out there should last long enough for you to get a full 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 regularly update this section with new findings.
A Note on Odor
In all of our tests, the silk and synthetic shirts constructed of polyester retain more smell over time than Merino wool tops. Merino wool can be worn for multiple excursions without washing before odor becomes an issue. Despite a company's best efforts to develop odor-resistant fabrics with polyester fabrics, most will inevitably smell over time, even after washing. If you're self-conscious about a bad-smelling shirt, choose either Tencel or Merino wool.
The Oasis Crewe features flatlock seams, which help prevent discomfort under a backpack and increase durability. Credit: Trish Matheny
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, splitboarding, 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 hold for the most current version. The high-quality design features a combination of Merrow and flatlock stitching that effectively holds the trim-fitting layer in place without limiting the wearer's range of motion. Our only caveat is that the fabric still has a slight smell. Aside from that, it has truly withstood the test of time and continues to exceed our expectations.
The Arc'teryx Rho features a highly durable construction; in fact, the only flaw is the fuzzy merrow stitching after interacting with the velcro on our ski bibs. Credit: Trish Matheny
While the Stio Trax Power Grid Half Zip Hoodie features a somewhat lightweight, see-through construction, we were impressed by the overall durability of Stio's power grid fleece and polyester. Rounding out our synthetic durability favorites is the REI Co-op Midweight, featuring reinforced flatlock seams and thicker, more comfortable thumb loops.
The Capilene Midweight and Stio Power Trax designs featured far more durability than the updated Capilene Thermal Weight that showed significant signs of wear after minimal use (as you can see in the last two photos above.
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 more durable, making them a better option for those needing a top for high-friction sports like canyoneering, bushwhacking, or rock climbing. The Ibex Woolies Pro Tech Crew is another Merino wool option that features Nuyarn technology in its lightweight design, along with a touch of nylon, which enhances the performance and durability of the ultra-fine Merino wool construction.
The Ibex Woolies Pro Tech Crew isn't the most durable option when compared to its synthetic counterparts, however, it does feature Nuyarn technology to reinforce the ultrafine Merino wool for lasting structure and performance. Credit: Trish Matheny
Layers like the Hanes Cool Dri Performance and the DEVOPS Thermal Compression Turtle did not impress our testing team in terms of durability, as we noted the stitching on both layers started to unravel and showed signs of wear after minimal use. While the light colors 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, they stain easily.
Though a highly affordable layer, the Hanes Cool Dri Performance doesn't match the durability offered by its high-performing counterparts, showing signs of wear in the stitching after limited use. Credit: Gus Landefeld
Drying Speed
Drying speed can truly make or break your day if you work up a sweat in your base layer, but don't want to cut the adventure short. 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-polyester blended layers offered the fastest drying times, much faster than their 100% Merino wool equivalents. We approached these tests from several angles, including drying on a line outside, on the body, and indoors overnight. Now, we can confidently report back on our top performers.
We tested each and every base layer side by side in order to objectively determine the layers with the fastest drying speeds. Credit: Trish Matheny
Air-permeable layers like the Stio Trax Power Grid Half Zip Hoodie were the fastest to dry in our controlled drying speed tests. Unsurprisingly, these base layers boast excellent breathability thanks to their porous fabric, which allows air to flow through and wicks moisture away from the skin.
During our controlled drying tests this spring, the Stio Trax Power and Patagonia Capilene Thermal Weight were among the fastest to dry. Credit: Trish Matheny
The Arc'teryx Rho Hoody dried in 40 minutes on the line and 25 minutes on the body, thanks to its lightweight, fast-drying Torrent stretch fleece and polyester construction.
The Arc'teryx Rho Hoody features an impressive drying speed despite its thicker construction without additional ventilation. Credit: Trish Matheny
Other impressive layers in this metric are the Ibex Woolies Pro Tech Crew, the Smartwool Classic All Season, the Ridge Merino Aspect Midweight, and the Patagonia Capilene Midweight Crew. It's no surprise that the ultralight Merino wool and synthetic-blended constructions of the Smartwool and Ibex designs dried faster than the thicker Ridge and Patagonia crews.
Ultralight layers like the Smartwool Classic All-Season feature faster drying speeds due to their minimalist design. Credit: Trish Matheny
Layering Ability
Base layers are not typically meant to be worn alone; thus, their functionality within a layering system is important to consider. You want to ensure that you can throw layers on top and remove them without having to deal with bunchy or twisted fabric. We evaluate the knit of the fabric and try 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 to help keep the sleeves pulled down. While most long-underwear tops are presumably your “next-to-skin” layer, it's a nice bonus when you can wear a tank or tee beneath when conditions are expected to warm up.
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 slimmer fit and a minimal design that also improves layering by reducing bulk, especially in the hood, which features a small opening for a ponytail, which makes it easier to layer with lots of hair.
Although the slim fit of the Arc'teryx Rho Hoody makes it difficult to layer underneath, the smooth synthetic fabric layers easily with other layers over top. Credit: Trish Matheny
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 and a super stretchy design that hugs the body. All are great options in this category. 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 well overall.
Smooth fabrics and slim-fitting designs typically make for easy layering.
Of the Merino wool competitors, thinner options like the Roman Trail Outfitters and the Smartwool Classic All-Season are much easier to layer than thicker options. The Ibex Woolies Pro Tech Crew and the Ridge Merino Aspect have close fitting cuts and feature helpful thumb loops that help you layer over top. Layers like the Kari Traa Rose and the Smartwool Intraknit Thermal work well, too, because they're fitted, making it easy to slide layers over them. Still, because of the fabric, all of these tops are going to stick more to a fleece midlayer or overshirt, and may take some adjusting.
The Ibex Woolies Pro Tech Crew is definitely one of the easiest to layer thanks to its ultralight and slim-fitting construction. Credit: Trish Matheny
How to Choose Base Layers for Women
Your base layer has a big job: keep moisture away from your skin while providing enough warmth, comfort, and mobility so you can focus on your activities without stressing about what you're wearing. Base layer tops are meant to be part of a system, facilitating thermoregulation based on whatever varied activities and weather conditions lie ahead. Below are a few key considerations our team has identified as important to review before you get started on your next purchase. For deeper insights on how to decipher your needs before you buy, take a look at our comprehensive buying advice for women.
Not every woman needs the same gear. Your planned activities, the climates and seasons in which they will occur, and your budget are all factors in determining which base layer is uniquely perfect for you. Credit: Trish Matheny
We love wearing wool layers for just about any cold-weather activity. The Ibex Woolies is our favorite lightweight merino option for warmer winter days. Credit: Trish Matheny
Which Material is Best?
Base layers were traditionally made from fine merino wool, and for a long time, that was considered the gold standard, even after synthetics (polyester, nylon, spandex, and the like) entered the scene. But today, synthetic fabrics are getting better and better as technology improves, and have some advantages over wool layers, especially for super active people. Merino-synthetic blends are becoming more common, with each unique combination aiming to merge the best of both worlds to achieve the perfect, high-quality, durable base layer. There have been some exceptional results.
Merino Wool
PROS
Great temp. regulation
Warmer
Naturally antimicrobial
CONS
Requires special care
Takes longer to dry
Poor shape retention
Merino wool has an incredible warmth-to-weight ratio, and is a great choice when you need to layer up to prioritize warmth. Think a day at the resort, where you'll be intermittently sitting on cold chair lifts, or during late fall camping trips. It is considered the top choice for garments of this type, thanks to its naturally wicking, antimicrobial properties that can provide superb warmth in wet and dry conditions and effectively resist body odor, even if you have to go a few days between washes. The “ultrafine” fibers are also very soft and easy on the skin (a far cry from that itchy wool sweater from your childhood). 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. If you want something to keep you warm and you don't plan to sweat a lot, wool is the way to go. Few other materials, natural or otherwise, can compete.
Synthetic fabrics like the one pictured above are typically more durable than their ultrafine Merino wool counterparts. Credit: Trish Matheny
Synthetic Fabric
PROS
Faster dry times
More durable
Better stretch and shape retention
CONS
Can hold odor
Not as warm
Not as great at thermoregulation
Synthetic layers are often better for high-output activities, where you generate more body heat and will likely sweat quite a bit. Think shoulder season trail runs, backcountry tours, and the like. They will breathe more, wick sweat better, and dry faster on the body. Synthetics also tend to be remarkably durable and come in a wide range of material combinations that address specific performance needs. Fabrics like recycled polyester, torrent, nylon, spandex, and elastane are often combined to deliver targeted results. 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.
Thicker synthetic designs like the one pictured above are great for trapping body heat although less breathable and offer prone to retaining body odor. Credit: Trish Matheny
Some other natural fibers, like bamboo, Tencel, alpaca wool, and hemp, are now finding space in the market as well. 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.
We love a good layer that is warm enough to wear alone on an early spring run, like the Icebreaker Merino 200 Oasis. Credit: Trish Matheny
What is Fabric Weight?
Base Layers come in three primary fabric weight options: lightweight, midweight, and heavyweight. As the name implies, lightweight layers are perfect for not-as-cold conditions. While not often worn on their own, they can be a reliable first layer against the skin during the winter months, providing a boost of warmth under your favorite fleece. What's nice about these is that their thin profile makes them much easier to layer. Midweight construction tops are perhaps the most versatile. They provide enough warmth and coverage to be worn independently and are 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 best suited for those who live or play in very cold climates. They offer the greatest warmth but the least versatility of the lot, since the thicker material is harder to layer, and may cause you to overheat more easily if worn in mild temps.
Sometimes you'll see fabric weight expressed in grams per square meter (GSM), which measures fabric density and weight. Not all companies list this spec for their base layers, but it can be a helpful way to estimate warmth. Lightweight layers are between 150-170 GSM, midweight layers are between 170-250 GSM, and heavyweight layers are between 250-400 GSM.
There are a variety of fabric weights, therefore, it is important to consider the climate you'll primarily be wearing your base layer as well as the activities you plan to pursue. Credit: Trish Matheny
What Fit and Features Matter?
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. You can size up if you prefer a looser fit, but this will increase airflow around your body and reduce overall warmth. Other features give you options in style, ventilation, and added performance benefits. Simple, slim-fit crew necks are easier to layer under casual clothing and are a great option for everyday wear. Options with zip necks, hoods, thumb loops, zipper pockets, are more performance oriented, meant for days in the backcountry. While not all tops have it, UPF protection is a welcome new feature that some companies are adding to their shirts.
There are some great options at budget prices that are particularly great choices if you are an occasional adventurer who doesn't require hardcore durability or the most extensive performance features. Credit: Gus Landefeld
Some base layer designs are basic while other layers offer features to enhance warmth, comfort, and breathability. Credit: Trish Matheny
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.
We had some fun putting these layers to the ultimate test while meticulously evaluating warmth, breathability, comfort and fit, durability, drying speed, and layering ability Credit: Meredith Jabis
