Best Base Layer for Women of 2020
Smartwool Merino 250 1/4 Zip - Women's
Wear this super comfy midweight top from the trail to your bed. The Smartwool Merino 250 ¼ Zip has fantastic comfort and versatility. Loaded with 100% natural Merino wool fibers, it provides one of the most extensive ranges of thermoregulation tested. It functions well as a long underwear top and a wear-alone top in temperatures ranging from the double negative digits to highs of 70 degrees Fahrenheit. It outperforms every other shirt in this review because of its ability to keep us dry and comfortable when conditions went from warm to cold and wet to dry. The fabric wicks away moisture, dries quickly when on, and doesn't stink.While the fabric is soft and cozy, the only thing that it truly lacks is durability against abrasive activities when worn without a layer over top.
The fabric is thick, though, and stands up to normal wear and tear well. We have noticed that this top can stretch out after multiple days of use. It will bounce back into shape, however, after being thrown into the dryer. Given its excellent quality, incomparably cozy fabrics, and excellent thermoregulation, we consistently recommend this top to our female friends.
Read review: Smartwool Merino 250 1/4 Zip - Women's
Best Bang for Your Buck
Carhartt Base Force Heavyweight 1/4 Zip - Women's
When we picked the Carhartt Base Force Heavyweight 1/4 Zip to test, we expected strong durability and functionality that this manufacturer is known for. Still, we had no idea we were selecting a top performer that this model proved to be. It feels just as soft as merino wool. It also wicks and offers durable construction, similar to a 100% synthetic top. When wearing it for many days on end, without washing it, the materials didn't build up odors and didn't stretch out. Furthermore, it's a queen when it comes to thermoregulation. It wicks well and efficiently moves moisture. While Carhartt calls it "heavy-weight," our team agrees that it is similar in performance to other midweight options on the market. The best part is the price. It's hard to find a product this high in value, especially considering that it features the convenient (and commonly more expensive) quarter zipper in the neck and chest.
The only thing that we've added to our wishlist for this top is a size adjustment. The materials are a bit stiffer than 100% merino wool, meaning the fabric doesn't stretch as much. The length through the arms and torso is about medium, but because it doesn't stretch, you can't pull the arms to get a little longer, which is also true for the torso. For fit, sizing up was key for our lead tester. All in all, if you're seeking a stellar deal for an all-around awesome polyester-wool base layer, this one can't be beat for the price.
Read review: Carhartt Base Force Heavyweight 1/4 Zip - Women's
Arc'teryx Rho LT Zip - Women's
After testing the Arc'teryx RHO Lt Zip for the last seven years, it stands out as our go-to synthetic for all technical missions. The interior is fleece lined with wicking power that does a good job moving moisture. We love the fitted design that is stretchy and incredibly easy to layer, with a zip-neck fit for optional venting purposes. It's 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, even after seven years of hard wear, it shows minimal signs of wear and tear. Tried, tested, and truly awesome.
This base layer doesn't offer the same level of breathability since the interior fleece layer that sits next to the skin can hold a little moisture when layered. Its high price isn't a huge plus either. However, given that this is one of the most time-tested pieces that we've had the opportunity of using, the value of performance you get out of it is definitely worth the price. This layer is best for a woman that is seeking a layer that's durable, technical, and looks great with color options.
Read review: Arc'teryx Rho LT Zip - Women's
Best for Breathability
Smartwool Merino 150 Crew - Women's
The Smartwool Merino 150 Crew is our top recommendation if you like to sweat and need a thinner, breathable base layer. Built with a synthetic & merino wool construction, it wicks away moisture efficiently while providing just enough warmth for those cold days. The lightweight construction makes it easy to strip it off in the summer and throw it in a backpack when the day heats up. What's more, after two years of consistent use, the fibers are holding up well, proving its excellent durability level over the years.
Those with sensitive skin might find the materials of this shirt to be a little itchy. While most of our testers (without this sensitivity) didn't notice it, some didn't like it. This tester preferred a base layer top construction that integrated more synthetic material and less merino wool. If you're seeking a highly breathable top that'll wick with a thinner construction, this is our top recommendation.
Read review: Smartwool Merino 150 Crew - Women's
Why You Should Trust Us
Our testing team is led by Amber King. As a seasoned gear reviewer, she has worked with OutdoorGearLab for over seven years, reviewing many different categories that reflect her tenacity and experience in the outdoors. She spends her time backpacking into remote places, canyoneering through slots deep in the earth, and finding cool trails to run worldwide. Hardcore women she meets along her adventures become additional testers to provide unbiased, diverse, and genuine feedback on all base layer tops tested. When she's not exploring, you can find her working with a local outdoor education non-profit she founded.
The base layer tops we test are used at a minimum for three months, and we continue to test them until they see an update throughout the year. When making our selection, we take hours researching the best options on the market before selecting the best to test. Then we buy each at retail and get them in the mail, our testing begins. We wear them everywhere we go. We've tested across the world, from the high glaciers of Alaska to the rainy and cool landscapes of Iceland. We take each trail running, backpacking, rafting, climbing, backcountry splitboarding, and hiking to determine how each perform in the backcountry, in unique situations. Once our field testing wraps up, we look at durability and objectively score each metric to determine how each product does comparatively.
Related: How We Tested Base Layer for Women
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 and 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 & fit, layering ability, and durability.
Wondering which top offers the best performance relative to its price? While the MSRP doesn't factor into our scoring metrics, we know just how important the performance received per dollar spent is. Typically, the largest trade-off in this category lies in the materials used. Merino wool tends to cost manufacturers more money than synthetic fabrics, and this higher price is passed on to the consumer. The Roman Trails Outfitters top is a merino top that retails for almost 50% less of our top performers. However, its thin materials that stretch out over time make it less durable.
Three of the lowest-priced models in this review are synthetic tops or blends, which present impeccable value. This includes the Patagonia Capilene Midweight and REI Co-op Midweight Base Layer Crew Women's. These crew tops are similar in price to our favorite high-value contender, the Carhartt Base Force Heavyweight 1/4 Zip. This top is similar to our top performers and does an amazing job in the field, for a fraction of the price. It is a synthetic-merino wool blend.
How many times have you started hiking, gotten your sweat on, then stopped only to shiver into movement once again? The tops that can keep you the warmest are those that will keep you warm while in action and while standing still. Different tops offer different weights of fabric, which dictates the warmth. In general, if you know you're going to 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 in cold weather, choose a thinner option. A midweight is always a good failsafe to look for.
When comparing fabrics, Merino wool stands out as the best thermoregulator. When looking at comparative weights, it offers more insulating warmth and breathability, which equates to better thermoregulation overall. For example, the Smartwool Merino 250 1/4 Zip is the warmest and most insulating base layer in this review, packing in 250 g/m² of merino wool. The Icebreaker Oasis 200 is similar, with 200 g/m², making it a little less warm and not as thick. The Kari Traa Rose H/Z is a super insulating top with a high density of wool packed in for a huge amount of warmth (240 g/m²).
Midweight tops like the Ortovox Rock n' Wool (185 g/m²) and Carhartt Base Force Heavyweight 1/4 Zip offers just a little less warmth but score high for warmth. Both are lighter options for excellent thermoregulation on high output days like cross-country skiing or running. The Patagonia Capilene Air (147-g) is another surprisingly warm contender that does excellent work at regulating heat output. For stand-alone warmth, it's among the top contenders.
Through our testing, most of the polyester tops we've tested don't offer the same 'sitting 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, cooling you down as well. However, when you start to move around, it'll heat with you. When moving from warm to cold, tops like the Patagonia Capilene Midweight Crew and Arc'teryx RHO Lt will typically adapt to their environment more readily than Merino wool. Both of these options are warmer synthetic tops than the REI Silkweight or Smartwool 150, for example, which are more breathable and not built for stand-alone warmth. Of them all, the Arc'teryx is our favorite because of the fleece liner built in that keeps the skin warm and cozy, even after the shirt has cooled down.
The yang to warmth's ying. Without great breathability, you're not going to have great warmth when playing in cool weather. A key metric for thermoregulation, it defines how well the fabric allows heat to escape in addition to 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.
The best breathers are those constructed with thinner materials and a fabric knit that isn't too tight to allow moisture to escape. The two that stand out in this metric include the Roman Trail Outfitters Merino Wool Crew and the REI Co-op Silk V-Neck. The REI Silk V-neck actually wicks and breathes a little better than the Roman Trail Outfitter because it's ridiculously light (only 2.4 oz) and has plenty of holes for ventilation through the fabric. Silk is also known for its superior wicking qualities. The Roman Outfitters is a little warmer, providing a wider range of thermoregulation, but it also vents well because of its loosely woven fabrics. We'd use both for summer wear but would leave the REI Co-op Silk at home in the winter. With a nicely layered system, the Roman Trail Outfitters also does good work under a fleece or jacket.
The Smartwool Merino 150 crew is a favorite for its lightweight construction and is far more durable than the Roman Trail Outfitters because of the integration of nylon into its construction. The weave, while breathable, isn't as loose as the Roman Outfitters, meaning there aren't as many holes in the fabric for ventilation. Both wick about equally. If you want more durable construction, we'd recommend the Smartwool Merino 150.
The Patagonia Capilene Air Crew features a loose weave that does an impeccable job wicking and offloading moisture. This top is thicker than the above lightweight contenders, but the fibers are full of air. This will keep you cool, but it's not suitable for full summer use because of its level of insulation. Through the shoulder seasons and winter, it's hard to beat because of its massive range of thermoregulation. The 100% synthetic construction of the Patagonia Midweight Capilene is also quite breathable. Its diamond-grid architecture promotes great airflow with a face fabric that cuts the win when worn independently. The REI Midweight (synthetic) also offers great airflow, but while hiking and skiing, we noticed that it helped more moisture in its fabric than the Capilene.
The Smartwool Merino 250 ¼ Zip, Arc'teryx Rho Lt, Icebreaker Oasis, and Ortovox Rock n' Wool all offer the same level of performance here. The Smartwool Merino 250 has a loosely knit fabric design but thicker fabrics than either the Ortovox Oasis or Rock n' Wool. The Oasis feels thinner than the Rock n' Wool but has a tighter knit construction. The Arc'teryx has a fleece lining that wicks away moisture with a synthetic fiber construction that promotes breathability. All of these options breathe well, but when put underneath a non-breathable layer, they all absorb a little moisture, unlike the REI Silk V-neck and Roman Outfitters Merino Wool options.
Comfort & Fit
Ah, comfort. What's better than wrapping yourself in fabrics that are as soft and smooth? When testing this metric, we assess each top to determine which has the coziest fabrics and the most versatile fit. This testing is the easiest - lazing about watching movies, hanging out around the campfire, going out with friends, and seeing how fabrics feel after day four of constant wear with no wash. In general, we love Merino wool tops with a fitted, stretchy design simply because it offers comfort while playing and sitting around at home.
The truly cozy and cuddle-worthy Smartwool 250 Zip is the most comfortable base layer top in this review. It features 250 g/m² of natural 100% New Zealand merino wool, a bit of stretch, with thicker cuffs and hemlines. It feels glorious against the skin with no itch and just cozy comfort. The Carhartt Base Force Heavyweight is another with a merino wool blend that's almost as soft as the Smartwool 250, but has materials that are a touch more rigid. The Smartwool 250 has a very stretchy and long fit, while the Carhartt's shape won't deform after being worn for days on end.
The Ortovox Rock n' Wool is another top performer featuring a lighter construction. It offers a fitted yet comfortable shape with fabrics that feel thin and insulate well. We commonly wore this while running snowy roads in late Fall. Upon coming home, there was no need to take it off as the fabric doesn't retain smells, and the fabric feels so good on the skin.
The Icebreaker Oasis 200 and Arc'teryx Rho LT are also seriously cozy. While the Oasis 200 is a little thinner than the Rock n' Wool with a tighter knit fabric, it is not as cozy on the skin. We love that the Arc'teryx Rho LT has a fleece liner on the inside of the shift that feels amazing against the skin. It also bounces right back into shape after days of wear. Unfortunately, while you can wear the Oasis from the trail into the house, we found ourselves wanting to peel off the Ar'cteryx Rho simply because the synthetic fibers feel a little colder after sweating and cooling down in them.Fit
When looking at fit, we handed these shirts to a group of women that varied in height, weight, and body shape. Some were tall while others were short, some had lots of curves, while others had none. In our evaluations, tops that had 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 (5'7", 145 lbs) prefers size Small in most of these tops but found the Kari Traa Rose, Ortovox 185 Rock 'N' Wool, Carhartt Heavyweight and Icebreaker Oasis to fit better in size Medium.
Need a shirt with long arms and torso? Luckily we have a host of options. Of synthetic tops, the Arc'teryx Rho LT has super stretchy fabric that provides a next to the skin fit. The Smartwool 250 1/4 Zip has a super stretchy construction with plenty of length through the arms and torso.
A good base-layer should easily be layered. While most long-underwear tops are presumably the "next-to-skin" layer, it is a bonus when you can wear a tank or tee underneath if conditions are expected to warm up. Not only that, but you want to make sure 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 each on with different layers. Long underwear tops that do best in this category feature slippery face fabrics, a thinner construction, and thumb loops.
Synthetic layers typically have more rigid fibers that, in combination, make for easy layering. The Arc'teryx RHO LT proves to be the easiest to layer. The frictionless face fabric slides smoothly against even the fleeciest of mid-layers. The arms are long and can be held when layering to avoid frustrating layering situations like those experienced with more friction competitors like the Smartwool 250 1/4 Zip.
The Patagonia Capilene Midweight is another great layering option with built-in thumb loops that keeps the arms in place, while the REI Co-op Midweight has frictionless face fabric and a super stretchy design that hugs the body. All are great options in this category.
Of the merino wool competitors, thinner options like the Roman Trail Outfitters, Smartwool 150, Icebreaker Oasis 200, and Ortovox Rock n' Wool are much easier to layer than thicker options. The Kari Traa Rose works well because of its super tight-knit weave and skin-tight fit that makes sliding layers overtop easy. For all the layers mentioned above, look for ones with longer arms so you can grab the cuff of the fabric while pulling on a mid-layer that might be more grabby.
The best base layers out there should last. It shouldn't shrink, stretch out, pill, or fall apart after just a few months of use. Most importantly, a durable top shouldn't see holes 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 wore each with loaded backpacks. After all of this, we inspect each product to evaluate the craftsmanship. In addition, we test each base layer continuously throughout the year and will update this section as we learn more.
In all our tests, the silk and synthetic shirts constructed of polyester smell more over time than merino wool tops. Merino wool can be worn for multiple excursions without washing before an odor becomes an issue. Despite a company's efforts to develop odor-resistant fabrics with polyester fabrics, most inevitably smell over time, even after washing. The long and short. If the stench is a sensitivity for you, choose merino wool.
It's been seven years since we started testing the Arc'teryx Rho LT Zip, and it's still going strong. Arc'teryx is known for its bomber craftsmanship, and this product is no different. We have used and abused it while climbing, hiking, split-boarding, and canyoneering. After many long years of use, there are still no significant areas of wear and tear. Our only caveat is that the fabric retains a little smell with some pit stains in sweaty areas. Aside from that, it's truly stood the test of time and continues to do so.
The Patagonia Capilene Midweight is a workhorse. The synthetic fibers are strong and retain shape, even after a few years of testing. It's no wonder it offers the best value of tops tested. The REI Co-op Midweight is also fairly durable, but the fabric is thin and pills easily after just a few washes. However, after two years of testing, it is still functional, minus some undone stitches here and there. The Carhartt Base Force Heavyweight 1/4 Zip is a top with heavy synthetic construction with merino wool. It proves to offer similar performance to our synthetic competitors, showing next to wear after heavy use and several washes.
Merino Wool contenders are less durable than synthetic options, but they don't hold onto odor. Of these, the Kari Traa Rose H/Z proves to be the most durable. Unlike the Smartwool 250 1/4 zip, Roman Outfitters Merino and Patagonia Capilene Air tops that have the least durable construction in this review, it offers a tightly-knit face fabric that doesn't 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, bushwacking, or rock climbing. The Smartwool 150 is another highly durable hybrid that continues to perform after a year of hard use. We are constantly impressed with its performance as it's seen over 400 miles of trail use and many rock climbing adventures.
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 at the ski hill, aim for one that performs to your individual needs. We've done the hard work and tested some of the best options out there, all to help you find precisely what you seek.
— Amber King