After researching 80 of the best long underwear bottoms for women on the market, we bought 10 of the most promising to test side-by-side. We wore each while battling big waves on the North Sea, staying warm in Canadian winters, and ski touring through powder stashes in Colorado. Running through early season snow really helped us determine comparative performance metrics, in addition to objective lab tests to find drying time, comfort features, and construction quality. After playing hard and lounging even harder, we give you a comprehensive, unbiased, and an in-depth look at the best next to skin options out there that'll keep your bum and legs warm and dry.Related: The Best Base Layers for Women of 2020
The Best Long Underwear Bottoms for Women
Best Overall Long Underwear Bottoms
Smartwool Merino 250 Bottoms - Women's
This base layer bottom is our favorite. It offers the widest range of thermoregulation and comfort while traveling from cool to cold climates. Stacked with 250-grams of merino wool fibers, it feels soft and cozy next to the skin. The fabric is naturally odor-resistant and withstands dirt and odors, making it a fantastic option for multi-day use (without a wash in between). All these excellent features, in addition to a versatile fit, make this piece our favorite long underwear bottom that we enjoy wearing all over the world. Use it on a cold day hike, car camping, or on your next backpacking mission.
Our only caveat lives with durability. Since the fabrics are so soft, they catch easily on sharp surfaces, and small holes can breakthrough. Snuggle up with a good book, or log the uphill miles in this fantastically warm, comfortable, and versatile long underwear bottom.
Read review: SmartWool Merino 250 Bottom - Women's
Best Bang for the Buck
Patagonia Capilene Midweight Bottoms - Women's
Notorious for its durable design, the Patagonia Capilene Midweight once again rises to the top for performance and value. Constructed of 100% recycled polyester, this pant offers a midweight construction that is versatile for all four seasons. The smooth face fabric retains its shape while thermoregulating efficiently. Its newest design update makes it thinner, easier to layer, and more comfortable than ever before. The cute patterns make it a perfect option to wear on its own or as a base layer under a pant.
It's hard to find much wrong with the newest update. While the polyester material isn't as cozy as those constructed with merino wool, it is still fit to be worn all day. Unfortunately, the fabric (despite its treatment) does get smelly after a few days of use, and because it's thinner, it seems a little less durable than previous designs. That said, we still believe this bottom will work hard for you, despite what you might put it through, while costing less than most.
Read review: Patagonia Capilene Midweight Bottom - Women's
Best for Synthetic Construction
Arc'teryx Rho LT Bottoms - Women's
New love has flourished for this exceptionally stylish and comfortable piece of long underwear. The super cozy Torrent fleece sits against the skin, offering great wicking performance. The thickness is just right, providing fantastic breathability with supreme durability. It has a long length and super stretchy fabrics, offering a great for all shapes and sizes. Not only that, but because of it's super cute colors and style, it can be worn on its own while climbing, hiking, or taking the dog for a walk. This makes it one of the most versatile synthetic competitors out there. We find ourselves wearing this long underwear bottom through all four seasons.
It's hard to find anything wrong with this product. The only real downside is the expensive price tag and the inherent problems associated with synthetic fabrics. It absorbs water but dries quickly. Aside from these minor issues, it's one of our favorites.
Read review: Arc'teryx Rho LT Bottoms - Women's
Best for Lightweight Construction
Smartwool Merino 150 Base Layer Bottoms - Women's
This super lightweight bottom is perfect if you run hot or want a layer that'll simply wick. The merino-synthetic construction offers a great blend of comfort balanced with powerful wicking capabilities and drying speed. Of the Merino base layers tested, this is one of the most durable, despite its lightweight design. This is a wonderful choice for ladies that like to sweat in the winter or want a sun layer for the summer. It's also one to consider if you have winter pants that are very well insulated and good ventilation.
While these lightweight bottoms sure can wick, breath, and dry quickly, they aren't very warm on their own. If you're planning on standing around in the cold, we'd opt for a thicker and more insulative layer. While they do work to wear on their own, be sure you get a darker color, as the lighter colors (if offered) can be a little see-through.
Read Review: Smartwool Merino 150 Base Layer Bottoms - Women's
Why You Should Trust Us
Amber King is an outdoor educator, adventurer, and gear tester. She has been testing gear for OutdoorGearLab for over five years, with a keen eye for detail, writing for over fifteen different categories. While she's climbing, snowboarding, hiking, sailing, and trail running, she's commonly wearing a great pair of base layer bottoms to keep her warm and comfortable on all adventures. She's tested them throughout the far reaches of the world. From sailing in the rainy climates of the Faroe Islands to trail running around the Cordillera Huay Huash in Peru. When she's not exploring, you can find her working on her non-profit that builds outdoor-based academic programs for high school students in Ridgway, Colorado.
When testing long underwear bottoms, we try to conjure up all the different ways they might be used. We take the time to take stock of what's on the market, selecting the highest rated products with the best reputations. Then, we test each product side-by-side after we buy it for retail price. This review has been alive for over two years, giving us the opportunity to test consistently through a plethora of conditions and temperatures during this time. We've tested internationally on sailing and running trips. However, most of our testing takes place in the Colorado Rockies, centralized around the small town of Ouray. This town is known for its ice climbing and skiing in the winter, and it's canyoneering, jeep roads, and amazing trails during summer. We do it all while wearing base layer bottoms for most missions through all four seasons.
Analysis and Test Results
A solid long underwear bottom needs to be a part of any woman's outdoor wardrobe. Designed to sit next to the skin, it wicks away moisture while you sweat to keep your skin dry. While these bottoms can be used on their own in warm weather, they are typically used in a layered system in the winter. In this review, we look at a range of base layer bottoms with a variety of weights. Testing them side-by-side, we evaluate them using four key metrics, including warmth, breathability, comfort, and durability.
While many expensive products reflect a higher value, that is not always the case. There are several products out there that provide similar levels of performance at a great price. These are typically the highest value options. When considering value, it's important to consider both the performance and durability. While the REI Midweight Bottoms offer the lowest price, this synthetic base layer bottom is super thin and doesn't offer the same level of warmth and durability as other well-built options. The Patagonia Capilene Midweight wins our Best Buy Award because of its awesome durability, warmth, and overall performance. The newest version is just as cozy as the REI Co-op Merino Bottoms but overall performance is simply better.
The insulative warmth of a base layer bottom is balanced with breathability to ensure great thermoregulation. When it comes to warmth, there are two different frames of thought. The first is that a warmer base layer will lead to better overall warmth. The second is that a base layer bottom should be as thin as possible, using an insulative system to add warmth. While neither is wrong or right, it just depends on what you prefer. Some like a super thin layer that will just wick away moisture, while others like a thicker layer that provide more next to skin warmth. When looking at warmth, know that most models come in different weights. The higher the weight, the warmer it will be. If you run cold, for example, choose a heavier weight. If you know you're going to be sweating a lot, or you already have super warm snow pants, a thinner bottom may be just what you need. If you're going to be sitting in the snow a lot, we'd recommend a more insulative layer.
During our testing period, we performed a few tests. First, we observed the different fabrics and make-up of each product. Then, we tested warmth by getting out into cold weather, from getting splashed by waves in the North Sea to sleeping under the stars during frosty nights in the desert. We carried our layers with us, cycling them out to see which offered the best insulative warmth on their own and underneath a pair of pants.
After our testing, we learned that the natural organic fibers of merino wool don't only feel amazing against the skin, but thermoregulates the best to offer fantastic warmth on the coldest days. Merino wool base layer bottoms, like the Smartwool Merino 250, provides the most warmth given its thicker fabric design and super insulative properties. Layers with a little less insulation like the Icebreaker Oasis and the Ortovox Rock 'N' Wool both have a little less insulation and a much thinner construction. The Oasis is a little warmer than the Ortovox.
While synthetic long underwear bottoms do great work drying quickly and staying cool, they usually aren't as warm. That said, some new synthetic bottoms are getting close to the warmth of merino wool. The Patagonia Capilene Thermal Weight is a pretty warm option loaded with a polyester-spandex construction. They are warmer than the Patagonia Capilene Midweight bottoms, given its thicker fabrics and a higher level of insulation. While these are warm when you wear them, they feel a little cold getting into, especially on cold mornings. The Arc'teryx Rho LT is advertised as a lightweight bottom, but actually feels like it has the same amount of thickness as the Capilene Thermal Weight.
What's unique about the Rho LT pant is the super cozy fleece lining that offers added warmth. Both these pants provide the ability to wear them on their own during cool weather in the summer. The Capilene Thermal Weight has a thicker face fabric that can cut the wind. The Rho LT is also built with this, but the fleece lining offers an even better barrier to the wind. Both offer great warmth when worn on their own and under a pair of pants. These are both the warmest synthetic options out there.
The Columbia Omni-Heat 3D Knit Tight is another synthetic that offers great warmth when in motion. However, it earns a comparatively low score in comparison to the rest because it cools down immediately as soon as you stop working. Best for running or other activities where you're going to be on the move, this base layer can offer great warmth, but only when in motion. The Patagonia Capilene Midweight offers more standing warmth while also providing warmth on the go, another reason it earns a Best Buy Award.
If you prefer a long-underwear bottom that doesn't insulate hugely, consider a lightweight design. These options are best for warm to cool weather, or while being active in cool weather. The sole purpose of these pieces is to wick away moisture without the added bulk of insulation. Our favorite is the SmartWool Merino 150 Bottom, made of merino wool and nylon. This blend adds wicking power and some durability, while the wool keeps the skin warm and happy. The REI Midweight is probably the thinnest of the base layer bottoms tested, with a synthetic construction. While it does a great job breathing, it isn't very warm. It can insulate underneath a good pair of insulated snow pants, but it's one of the coldest tested.
Breathability and drying speed work together to ensure that your long underwear stays dry, whether you're pushing the aerobic threshold or simply hanging outside. To test breathability, we looked at the thickness and type of fabrics. In addition, we took each piece running to determine how the fabric allows sweat to wick away from the body. After our sweaty runs, we looked at the fabric to see if moisture retained in the fibers, or if it easily evaporated away. We also wetted each piece, figured which absorbed the most water, and which dried out the quicked using an at-home dryer.
It's not surprising that the fastest base layer bottoms to dry are those that are the thinnest. The thinner materials allow air to pass through more readily, thus allowing evaporation. The best breather of the groups is the SmartWool Merino 150 Bottom, winning our Top Pick Award for its ultralight construction. This top integrates nylon fabrics that do a great job at breathing quickly, while the merino wool is porous enough to allow moisture to evaporate readily. This was a common base layer we used for backcountry splitboarding underneath or pants that lack insulation.
Following this in the breathability game are the synthetic competitors, which isn't too surprising. Synthetic fabrics are known for their great breathability and fast drying speed. On trail, the Patagonia Capilene Midweight is the fastest to dry with its thinner construction. The REI Midweight offers a similar drying speed, with a design that is a touch thinner, but the fabrics are knit more tightly than the Cailene Midweight.
Both Patagonia Capilene models actually showed a similar drying speed. Even though the Capilene Thermal Weight has more material and absorbs more water, it's able to transfer moisture just as well as the Capilene Midweight pant. If we had to choose between them for running or super aerobic activity, we'd opt for the Capilene Midweight as it doesn't hold any moisture in the fabrics and is a much thinner construction.
Of the thicker wool contenders, the Ortovox Rock 'N' Wool and REI Merino Midweight have a similar level of performance. While the REI Merino is said to have a heavier construction, the Rock 'N' Wool looks to have the same thickness and performed the same while testing on runs and the like.
Thicker base layers like the Smartwool 250 and Arc'teryx Rho LT also offer great breathability but are not as quick to dry. While both are thicker in construction, if either is worn with a pair of pants that lack ventilation, moisture can accumulate in the fabrics. When this happens, the wool contenders typically do better as wool has a better ability to retain heat than synthetic fabrics. That said, with good ventilation, both are built to breathe well.
If you seek a breathable layer, you're in luck! All the pieces in this review breathed and dried effectively. If you want the best in this category, look for a thinner weight. It seems that merino wool offers more warmth when wet, but synthetic fabrics do a better job at wicking and drying quickly. The pants that integrate both materials offer the best breathability that we've seen thus far.
Comfort and Fit
A long underwear bottom that'll feel cozy from the hill to your bed (without taking it off) is the best you can find. One that fits right is also going to be comfortable next to skin all day while adventuring. So, we took the time to evaluate the comforts in this metric. Fit is not scored, as it is a subjective variable, but we take the time to explain which will do well for what body type. When testing these metrics, we put each bottom on, looked at the seams, and observed how it felt to wear all day long. We chilled out, we sweat, we drank coffee, we sang songs. Through it all, we identified a few favorites, even though all contenders feel relatively comfortable and are fit for all-day wear.
Soft, cozy, roasty, toasty. The Arc'teryx Rho Lt Bottom is one of our favorites. While most synthetics fabrics can feel stiffer, the Torrent fleece used in this bottom is super cozy and warm. Against the skin is an actual fleece layer, which no other base layer bottom has. With its stretchy fit, it's by far one of the most comfortable base layers we've ever tested, earning a perfect score in this category. We love that the style is versatile enough to wear on its own or underneath a pair of pants.
The Smartwool Merino 250 bottoms are also quite comfortable. While you can wear it on its own, the fabric sags and doesn't look as good as the Rho LT on its own. Like many other merino wool contenders, it's best worn underneath another layer, or as loungewear around the house. Other heavier merino wool bottoms like the REI Merino Midweight, Icebreaker Oasis, and Ortovox Rock 'N' Wool are also super comfortable. Of them, the Rock 'N' Wool has the softest material on the skin, though it's also the thinnest, so it's not as cozy as the other two options. All of those tested are great for all-day wear.
The Smartwool 150 is another super comfortable option. It integrates nylon into its construction, which helps to wick away moisture effectively while the material is primarily merino wool, so it's soft to the touch. It fits tighter than the 250 version. As a result, it's better suited to wear on its own if you so choose. Just make sure you order a darker color as the lighter color can be almost see-through.
Other synthetic contenders offer great breathability but aren't as comfortable as the wooly competition. The materials are all soft and feel good against the skin. However, they aren't cozy. In addition, because the fibers are "hollow," they get colder quickly, which means for a less comfortable experience if the temperature in the room drops. Of synthetic competitors, we like the Patagonia Capilene Midweight bottoms the most. The thinner fabrics are soft against the skin, similar to the REI Midweight but don't get as cold as easily.
The Capilene Thermal Weight is also comfortable, but the fabric feels stiffer than the thinner version with a more abrasive waistband than all competitors, leaving it in the dust. The REI Midweight and Columbia Omni-Heat score about the same level. While the REI is super thin and gets cold easily, the Omni-Heat offers much better insulation and thus comfort. That said, we aren't big fans of the "reflective" technology on the OmniHeat that sticks to the leg when you pull it on. When you finally get the pant on, this is not a problem, and the pant is perfectly comfortable, but before that, you've really gone to work to get it on.
Durability is key to buying a high-value product. You don't want to invest in a pair of base layer bottoms only to find out that they wear down after just a few uses, or they're going to fall apart. When being layered underneath other layers, or on its own, the fabrics are going to rub against other fabrics and the environment. To test durability, we observed wear and tear after our testing period. We hiked, skied, climbed, and ran with each, both layered and on its own. We evaluated the quality and craftsmanship of every product by looking at its seams and stitching, noting any fly-aways or red flags. After walking through bramble bushes and thrashing each while crack climbing, we've got a pretty good idea of which products are more durable than others. Our testers have also owned many of these models for years and added their long-term feedback to our testing notes.
If the most durable bottom out there is what you want, look for a thicker construction made from synthetic materials. The strong fibers are stiffer in construction, another reason synthetics are not as absorbent and breathe quite well. They are also more resistant to abrasion and bounce back into shape when stretched and worn. The Arc'teryx Rho Lt (84% polyester, 16% elastane) and the Patagonia Capilene (100% polyester) options are both built to take on the tough stuff.
Between the two of them, the Capilene Thermal's show more resilience. The face fabric is thicker and more resistant to abrasions. The Rho LT has lasted us many years, but the stitching is upending and coming apart, while the fabrics are starting to wear through. That said, we've been rock climbing in them (on their own) and wearing them like crazy over the last two years.
The Capilene Midweight is also a more durable base layer bottom, but the newest version went away from its thicker face fabric design to thinner fabrics. While we've only tested this bottom for a short period of time, we believe it won't be as durable as the previous version, simply because the face fabrics are smoother and more prone to snags. That said, after our testing period, we haven't seen any signs of poor craftsmanship and still believe it'll last for years, just like the previous design.
While merino wool isn't as durable as synthetic fibers, it's not like they fall apart after a few months of vigorous use. Bottoms that integrate both merino wool and synthetic fibers into the construction, like the Smartwool Merino 150 prove to be the most durable.
Others with a thicker construction would seemingly be more durable as there is more material. However, we've found that these thicker contenders actually snag more easily and pill faster than thinner options. Of the merino wool bottoms made only with this fabric, the Icebreaker Oasis proves to be the best. The material is tightly knit, and even for its thinner construction, it seems super burly. The Ortovox Rock n' Wool is close behind, even featuring thicker fabric reinforcements in the knees, a high wear area. The thinner materials throughout seem paper-thin, and while we didn't observe any holes, we wouldn't be surprised if it wore through with some heavier use. That said, we do appreciate the additional material on the knees where there would be a little extra wear.
We've come a long way since long underwear was super thick, itchy wool suits or dimpled cotton. A great long underwear bottom is the foundation of the cold-weather outfit. While there are plenty of options to choose from, be sure you determine what kind of weight you need and the performance that you want. We wish you happiness on your mission to find your next bomber base layer bottom.
— Amber King