Best Long Underwear for Women of 2025/26

Women's Base layer bottoms and thermal underwear bottoms to stay warm in cool weather

woman on top of mt st helens wearing baselayer bottoms

November 29th, 2025, updated with a new heavyweight winner, a years' worth of testing notes and photos, a care and maintenance section, and to remove discontinued products
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When the cold sets in, long underwear becomes your trusted first layer—it keeps you warm, wicks away moisture, and lets you stay comfortable whether you’re snowshoeing, hiking, skiing, or just lounging in base camp. Choosing the right pair means balancing fabric, fit, and activity so your legs stay dry, warm, and unrestricted.

After reviewing dozens of options and narrowing the field to 12 top women’s base‐layer bottoms, our tester—an experienced thru-hiker, mountaineer, packrafter and back-country skier—wore each pair across two years of varied adventures. From volcanic ascents to snowy hut trips and remote canyon packrafts, these garments were tested in real, raw conditions to see which ones genuinely perform.

Our evaluation focused on three essential performance zones: fabric and insulation (merino vs synthetic, lightweight to heavyweight), fit and comfort (waistband design, sizing inclusivity, mobility), and durability across repeated use and wash cycles. We also weighed versatility—how well each bottom layers, transitions from active outings to rest days, and meets demands across terrain and weather.

Top Pick: The Smartwool Women’s Classic Thermal Merino Base Layer Bottom earns our Best Overall award. With ultra-soft 100% merino fabric, a wide size range (XS–4X), and consistent performance from winter’s edge to alpine ascents, it emerged as the go-to bottom for most multi-sport adventurers.

Looking for men's long underwear? See our Best Men's Long Underwear guide. Looking for more women’s underwear for the outdoors? 

Looking for base layer tops? See our Best Base Layers guide.


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Women’s long underwear comparison table

WOMEN'S LONG UNDERWEAR BOTTOM TREELINE AWARD MSRP* MATERIAL WARMTH WAIST SIZES WEIGHT (OZ)**
Smartwool Classic Thermal Merino Base Layer Bottom Best overall
Read why
$115 Wool Midweight Mid XS-XL, 1X-4X in extended sizes 7.5
Arc'teryx Rho Best synthetic
Read why
$100 Synthetic Lightweight High XXS-XXL 5.3
Mons Royale Cascade Merino Flex Best lightweight
Read why
$120 Wool Lightweight Mid XS-XL 4.9
Arc'teryx Rho Heavyweight Best heavyweight
Read why
$120 Synthetic Heavyweight High XXS-XXL 8.1
Ridge Merino Inversion Best affordable
Read why
$80 Wool Heavyweight Mid XS-XL 7.3
Icebreaker 260 Tech Mid Rise Best hiking
Read why
$125 Wool Midweight Mid XS-XL 7.3
Smartwool Intraknit $130 Hybrid Mid to Heavy Mid XS-XL 9.3
Icebreaker 200 Oasis $105 Wool Lightweight Mid XS-XL (REI also has 2x and 3x?) 6
Icebreaker Oasis 200 High Rise Base Layer Bottom $95 Wool Midweight Mid XS-XL 7.8
REI Midweight Base Layer tights $55 Synthetic Midweight Mid XS-3X, Petities: XS-XL 6.7
REI Merino 185 Base Layer Bottoms $80 Wool Lightweight Mid XS-XL 5.6
REI Lightweight Base Layer Tights $40 Synthetic Lightweight Mid XS-XL 5.8
Patagonia Capilene Midweight $79 Synthetic Midweight Mid XXS-XXL 5.5
Helly Hansen Lifa $100 Hybrid Midweight Mid XS-XL 10.5
SOURCE: Manufacturers

* We often find these available below MSRP. See our Deals Page for more info.

**Weights measured on our scale.



The winners

Smartwool Classic Thermal Merino Base Layer Bottom

Material: 100% Merino wool 
Available sizes: XS-XL, also available in plus sizes 1X-4X
Waist: Mid-rise
Weight: Midweight, 250g/m2
Garment weight (size M): 7.5oz
What we liked: Soft fabric, wide waistband without any digging, huge range colors and patterns, extended sizing
What we didn’t like: No crotch gusset

We think the Smartwool Women’s Classic Thermal Merino Base Layer Bottom is the all-around best long underwear choice for most people and activities. The moment I first tried these on, I knew they would be a favorite. The fabric is super soft on the skin with no itchiness from the start, which is extra impressive because the fabric is 100% merino — no synthetic blend!  

What really makes the Smartwool Classic Thermal Base Layer Bottom stand apart from other base layer bottoms is the waistband construction. Instead of relying on a separate elastic band sewn on top, which tends to dig into the skin and create uncomfortable pinch points, the Smartwool Classics encase the elastic in the same merino fabric as the rest of the bottoms. This construction helps distribute the pressure evenly and create a secure fit without feeling constricting.

Compare prices of the Smartwool Classic Thermal Merino Base Layer Bottom

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Woman hiking in Smartwool Classic Long Underwear

I tested this base layer in a variety of outdoor activities, including one memorable snowshoe trip in the dark to a remote cabin when it was 33F and pouring rain the entire time. The Smartwool Classic bottoms kept me warm and dry under my rain shell — no clamminess at all.  Because they are so cozy and comfortable, I also find myself wearing them simply to lounge around the house. The fabric is sturdy and durable, and while I always try to be careful with my merino garments, I don’t feel the need to baby these Smartwool bottoms. They have held up beautifully to regular use.  

The only feature I would’ve liked to see in these bottoms that is missing is a fully gusseted crotch for a little more range of motion. However, I found the more minimal diamond crotch and flatlock seams to be quite comfortable, and the inherent stretch of the merino knit allows good mobility.

The Smartwool Classics are available in a multitude of fun colors and patterns, as well as classic solids. Additionally, these base layer bottoms are available in the widest range of sizes of any of the base layer bottoms we tested, XS through 4X.  

Customer reviews echo all the same reasons we praise the Smartwool Classic bottoms: the soft and cozy fabric, toasty warmth and breathability, and great fit.


Best synthetic long underwear: Arc’teryx Rho Bottoms 

Arc’teryx Rho Bottoms 

Material: Synthetic - Torrent™ 190 with Polygiene®- 84% polyester, 16% elastane
Available sizes: XXS - XXL
Waist: High-rise
Weight: Lightweight
Garment weight (size M): 5.3oz
 What we liked: Durable fabric, quick drying, excellent fit
What we didn’t like: Pocket too small for most phones. 

The Arc'teryx Rho Bottoms are our winner for best synthetic women's long underwear. The Arc’teryx Rho Bottoms have the most intricate patterning of all the base layers we tested, and it shows. The fit is superior as well as stylish. The wide paneled waistband covers a narrower elastic band that keeps the bottoms from falling down. A fully gusseted crotch makes for chafe-free movement, and seaming below the knees keep the fit dialed in throughout the entire length of the legs. 

Compare prices of the Arc’teryx Rho Bottoms

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The synthetic fabric also has a smooth feel on the outer face and layers glide over the fabric easily. The high elastane content of the fabric makes the Arc’teryx Rho Bottoms very stretchy, fitting a variety of body shapes well. We had several testers wear these long underwear bottoms–from people with curvy, muscular thighs and bottoms to more narrower legged people. In each case, we were surprised by how well the same pair of size medium long underwear bottoms fit such different shaped bodies.

These bottoms not only serve as a great layering piece, but provide enough modesty that they can easily be worn by themselves as leggings. The fabric is opaque, the seaming is very sleek, and there’s even a zippered pocket on the right thigh that fits a credit card, cash, or keys. Unfortunately, the pocket is a bit too small for most cell phones. 

I found myself regularly grabbing the Arc’teryx Rho bottoms for quick hikes in Forest Park, my local trail system. Because they were one of the few pairs of long underwear we tested that were modest enough to wear by themselves, they’re so convenient to wear for shoulder season days where the mornings start out cold. I could easily throw a pair of hiking pants over the Rhos, and then when temps warmed up, I could take off the pants and just wear the Rhos. This system was much easier than removing the inner layer, as I would've had to do with most other long underwear bottoms! 


Best lightweight long underwear: Mons Royale Cascade Merino Flex Legging

Mons Royale Cascade Merino Flex Legging

Material: blend 81% merino, 12% nylon, 7% elastane
Available sizes: XS-XL
Waist: High-rise
Weight: Lightweight
Garment weight: 4.9oz
What we liked: Comfy waistband, fun colors, performance of fabric blend
What we didn’t like: Not as soft as others

I was initially attracted to the Mons Royale long underwear because of the fun prints and colors, but I was pleasantly surprised to find the Cascade Flex Leggings also ended up being a comfortable and high-performing lightweight base layer. The Mons Royale Cascade Merino Flex Legging is our winner for best lightweight long underwear. At 4.9 oz, not only was it the lightest baselayer bottom we tested, but also performed well in varied conditions.

Compare prices of the Mons Royale Cascade Merino Flex Legging

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The lightweight blend of 81% merino, 12% nylon, 7% elastane makes for a good balance of breathable, stretchy, and quick drying.  Upon initial try-on, the fabric felt slightly itchy, but disappeared after a few hours of wear, and remained soft on all subsequent wears. 

Despite not having any crotch gusseting or waistband paneling, the fit was good on my athletic thighs and butt, and I didn’t notice any chafing or rubbing thanks to the flatlock seams. The wide, soft elastic waistband stays in place. Of all the models we tested with a separate sewn-on elastic waistband, this was the most comfortable.

Testing included a spring snowshoe climb of Mt St Helens, where the Mons Royale Cascade Flex’s light weight was just right for next to skin comfort under softshells while laboring uphill in the sun, withstanding gusts at the summit, and glissading down the mountain. 


Best heavyweight Long Underwear: Arc'teryx Women’s Rho insulated hybrid Bottom 

Arc'teryx Women’s Rho Heavyweight Bottom 

Material: Synthetic - Polartec® Power Stretch® Pro - 53% polyester, 38% nylon, 9% elastane
Available sizes: XXS - XXL
Waist: High-rise
Weight: Heavyweight
Garment Weight (size M): 8.1oz
 What we liked: Versatility to be worn as standalone legging, excellent fit, soft and cozy
What we didn’t like: Expensive for synthetic, pocket is too small for larger phones

The Arc’teryx Rho Insulated Hybrid Bottoms were easily the warmest of the long underwear we tested and win our award for best heavyweight long underwear bottoms. In addition to the toasty warmth, we loved the comfort of the Arc’teryx Rho Insulated Hybrid bottoms. The Polartec Power Stretch Pro fabric has a super soft fleece interior, making for a very cozy next to skin feel while the outer face of the fabric is a sleek and durable nylon.  

These are true multitasking bottoms. I found myself wearing them as standalone pants for everything from lounging around the house to going on a run in the snow. The Arc’teryx Rho Insulated Hybrid bottoms have all the comfort of lounge pants but the fit and styling to make them suitable for wearing alone as leggings.

Compare prices of the Arc'teryx Women’s Rho Insulated Hybrid Bottom 

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The fit of the Arc’teryx Rho Insulated Hybrid bottoms is the same as the Arc’teryx Rho bottoms: it’s great on multiple body shapes thanks to the high rise fit, smartly paneled wide waistband, and the super stretchy fabric. A narrow, fully encased elastic band at the top of the waistband keeps the bottoms from slipping down. The low-profile zippered thigh pocket is handy for small items, though not big enough to fit a cell phone.

It's worth noting that for some activities and some climates, they may actually be too warm, especially if wearing them as a layer under other pants. If you aren't sure, consider the Arc'teryx Rho we recommend above.


Best affordable long underwear: Ridge Merino Inversion

Ridge Merino Inversion

Material: 100% merino wool
Available sizes: XS-XL
Waist: High-rise
Weight: Heavyweight - 270g/m2
Garment weight (size M): 7.3oz
What we liked: Affordability, soft fabric
What we didn’t like: Simple construction/less dialed fit

The Ridge Merino Women's Inversion Heavyweight Merino Wool Base Layer Leggings are a great merino option at an affordable price. The 100% merino fabric is super soft, with all the benefits of wool’s warmth and breathability. 

While the construction and fit is more basic, lacking shaping panels through the waist and rear, it still has nice features like flatlock seams and a small triangle crotch panel. The elastic waistband is brushed on the inside, so it is fuzzy and soft against the skin. Some folks may appreciate the higher rise fit of the waist for extra coverage.

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Ridge Merino Inversion

At 7.3 oz, these are one of the heavier-weight options we tested, and may be too hot for vigorous activity in all but the very coldest conditions. The Ridge Merino Inversion leggings are ideal for activities like camping, resort skiing, and snowy walks.

I used the Ridge Merino Inversion leggings on an overnight winter snowshoe cabin trip. I was dry and comfortable on an easy 3 mile snowshoe in and out, and also toasty warm while sleeping and lounging by the woodstove in the cabin.

The Ridge Merino ticked all the boxes I wanted for a luxurious feeling base layer bottom at a more affordable price than many other options.


Best hiking Long Underwear: Icebreaker 260 Tech Merino

Icebreaker 260 Tech Merino

Material: 100% Merino wool
Available sizes: XS-XL
Waist: Mid-rise
Weight: Midweight
Garment Weight (size M): 7.3oz
What we liked: Superior breathability, excellent warmth without bulk
What we didn’t like: Not the softest of fabrics against the skin, fit is more basic

The Icebreaker Women's Merino 260 Tech Thermal Leggings are our favorite choice for activities that fluctuate in intensity, such as hiking and snowshoeing. The 100% merino fabric is knit in a way that enhances breathability compared to other fabrics of a similar weight (260g/m2). The Icebreaker's merino wool is exceptional at regulating heat when powering through high intensity activities while also retaining warmth during periods of rest. 

Compare prices of the Icebreaker 260 Tech Merino

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The Icebreaker Merino 260 Tech Thermal Leggings fit well thanks to a back panel yoke and crotch gusset. The mid-rise height still provides good butt coverage for my muscular bottom, and the elastic waistband is soft and doesn’t dig into the skin while still being secure.

The highly breathable fabric is soft and warm, though the feel against the skin is not quite as plush and cozy as other models. 

In addition to the garment performance, Icebreaker's commitment to sustainability is commendable, with significant strides towards eliminating plastic from their products, achieving an impressive 96% plastic-free status in 2023.

Their dedication to sourcing wool from producers that engage in regenerative practices further underscores their responsibility towards environmental stewardship.

Think hiking long underwear is too much warmth for you? Consider hiking tights instead, which often have pockets. These aren't designed for layering like a hiking base layer bottom, but can sometimes still work in cooler temperatures.


Other women’s long underwear we tested

Smartwool Intraknit Thermal Merino Base Layer Bottoms

Smartwool Intraknit Thermal Merino Base Layer Bottoms

Material: Blend 52% merino wool/45% polyester/2% elastane/1% polyamide
Available sizes: XS-XL
Waist: High-rise
Weight: Midweight
Garment weight (size M): 9.3oz
What we liked: Knit integrates shaping and ventilation without extra seams
What we didn’t like: Uncomfortable fabric feel and slim/compressive fit

Many reviewers liked the Smartwool Intraknit bottoms because they are made with a hybrid fabric and knitted-in pattern that yields great breathability and comfort.

However, this knitted-in articulation was also problematic for some bodies (including mine) when the knee shaping didn’t line up with my knees. I also found the fit to feel constrictive through the thighs (I have muscular thighs from many years of Crossfit). For my body shape, the compression-like fit felt uncomfortable. Other testers and I found the ventilation panels felt itchy against the skin.

Compare prices of the Smartwool Intraknit Thermal Merino Base Layer Bottoms

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Smartwool Intraknit Thermal Merino Base Layer Bottoms

Icebreaker Merino 200 Oasis Thermal Legging

Material: 100% merino
Available sizes: XS-XL
Waist: Mid-rise
Weight: Lightweight
Garment Weight (size M): 6.0oz
What we liked: Good breathability and light warmth
What we didn’t like: Not the softest fabric, fairly sheer

We tested the Icebreaker Merino 200 Oasis leggings, and while there’s nothing particularly bad about them, we liked some other options better. This lightweight Icebreaker fabric performs well, but it’s not quite as soft as others like the Smartwool Classic. The fit and waistband is not quite as comfortable as our lightweight winner, the Mons Royale Cascade Flex. The Mons Royale is also more than an ounce lighter.

Compare prices of the Icebreaker Oasis 200 High Rise Base Layer Bottom

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Icebreaker Merino 200 Oasis Thermal Legging

Why you need long underwear

We wore long underwear until mountaineering and ski pants on adventure trips all winter. Here the author is changing out of wet outer pants in a trailhead parking lot.

We wore long underwear until mountaineering and ski pants on adventure trips all winter. Here the author is changing out of wet outer pants in a trailhead parking lot.

The benefits of long underwear

Long underwear is essential for outdoor activities to provide insulation and moisture management to keep you warm and comfortable in cold conditions. Long underwear allows for versatility with layering under other garments like hiking pants or hard shell snow pants.  Other baselayers like winter running tights that are designed to be worn alone are bulkier and often have features like pockets that don’t fit well under layers. In contrast, hiking tights don't layer as well as long underwear and are often bulkier with more pockets. 

Using long underwear for layering

Layering allows you to adapt to variable conditions, and long underwear serves as the foundational layer. Long underwear is recommended when the temperatures fall below freezing, or even warmer if you tend to get cold easily.  Outdoor winter activities like skiing and hiking can also expose you to chilly winds and snow. Making sure you are dry and warm is essential, and that starts with an insulating and wicking baselayer right against your skin. You can learn more about layering for cold weather activities in our guides to How to Hike in Winter and How to Layer for Skiing

Versatility for various activities

A good base layer can be worn for all kinds of activities, from hiking and snowshoeing, or skiing, to simply hanging out by the campfire, keeping you warm and dry while still allowing a full range of motion. 


What to look for in long underwear

The author changing out of wet outer clothing into the Smartwool Classic base thermal layer bottoms after a snowshoeing trip.

The author changing out of wet outer clothing into the Smartwool Classic base thermal layer bottoms after a snowshoeing trip to a fire tower.

Material

One of the biggest considerations in selecting a base layer is the choice of material.  Synthetics, primarily polyester and nylon, are great at moisture wicking, are quick to dry, and are affordable.  One of the biggest potential downsides to synthetics is their tendency to get smelly.

Cotton is also a common long underwear material (think cartoon long johns in a waffle texture) and while comfortable and cozy for lounging around the house, cotton holds onto moisture, making it a poor choice for active pursuits and outdoor activities.  

Wool as a next to skin baselayer may sound uncomfortable, but merino wool (from merino sheep) is a soft, natural fiber that is comfortable, and offers excellent insulation properties. It regulates body temperature, wicks moisture away from the skin, and even resists odor. Merino wool is ideal for outdoor activities and can be worn for extended periods without getting funky.  While a great material choice, it is generally the most expensive fabric option.

All the long underwear we tested all hanging over a wooden fence

Insulation and thickness

Weather conditions, temperatures, and activity type will determine how much insulation you need in your baselayer. Colder ambient temperatures will of course warrant heavier insulation to stay warm. However, your body will produce more heat with high output activities, like snowshoeing or strenuous hiking, and selecting too warm a layer will result in excessive heat and sweat.  

Warmer base layers are generally referred to with terms like “heavyweight.” 

Merino weight is generally specified in terms of grams per square meter of fabric.  Common weights are:

Lightweight: ~200 gsm or less

Midweight: ~250 gsm

Heavyweight: ~300 gsm or more

Moisture-wicking

Both synthetic and merino wool perform well at wicking moisture away from the body. This is important to keep you dry and comfortable, as well as keep you warm.

The author changing out of base layers in a trailhead parking lot in Washington post-adventure.

The author changing out of base layers in a trailhead parking lot in Washington post-adventure.

Breathability

Breathability is key to allow some air circulation, regulate temperature, and prevent moisture buildup, keeping you from feeling clammy. Synthetics can do a good job of this depending on the construction of the fabric, and merino excels at breathability.

Icebreaker Oasis 200

Fit

Proper fit is key to a comfortable, well-performing base layer. Bodies come in a wide range of shapes and sizes, and different brands, styles, and construction methods will fit everyone a bit differently. Well-fitting waistbands that stay put and prevent the long underwear from sliding down are key.  A snug next-to-skin fit that isn’t constrictive will provide the best insulation, moisture wicking, and comfort. 

Some of the long underwear we tested laid out on a table

Design

Design details can improve fit, function, and comfort.  Look for wide elastic waistbands that distribute pressure evenly and prevent rolling or digging into your skin. Flat seams reduce bulk and irritation and are more comfortable against the skin.  Paneled construction can help the fit better contour to the body.  Gusseted crotches reduce seam bulk and chafing, and allow for better range of motion.  

Durability

Durability is a key consideration in selecting a base layer since it is worn for so many activities and will see a lot of use. Fabric and seams need to hold up to extended use and laundering.

Sizing

Long underwear is typically sized in straight sizing (XS through XL). Icebreaker and Smartwool offer extended sizing (up to 2X and 4X, respectively) in some styles.

Odor resistance

Merino takes the cake in odor resistance and can be worn many times without washing and without smelling bad. Synthetics need to be washed more often to prevent unpleasant odor accumulation.

Ease of care

Synthetics are the easiest to care for, easily machine washed and dried. Merino wool may sound intimidating, but it’s surprisingly easy to care for. We machine wash all our merino, and even throw it in the dryer on low heat sometimes (manufacturer recommendations vary, but some do endorse machine drying on low heat).  

All garments, regardless of material, will last longer if washed less frequently and line dried.  Thanks to its odor resistance, merino needs to be washed less frequently, so line drying it on occasion isn’t too much of a hassle. 


Stacks of folded women's long underwear we tested

Buying advice

What activity or activities are you buying the long underwear for?

When considering which long underwear is best for you, consider first the type of activities you’ll be engaging in and the weather conditions you’ll experience. With high-output activities like snowshoeing, cross-country skiing, or backcountry skiing, a lightweight layer will likely be a good choice, whereas you may want a warmer layer for hiking in cold weather, or resort skiing where you may spend a significant portion of your time waiting on a ski lift. 

You'll also want to consider the fit of the garment and how it works with your other layers and equipment. For example if you're backpacking ask yourself, "Iis the waistband comfortable under a backpack hip belt?".

You should also consider what type of material you prefer. The natural fibers of merino wool provide outstanding breathability, moisture wicking, and odor resistance, while synthetics dry the most quickly and are typically more durable and less expensive. 

Arcteryx Rho Heavyweight

What specific weather conditions will you be facing during your outdoor activities?

Outside temperatures and types of activities will be the main drivers of how warm a baselayer you choose. The colder it is, the heavier-weight bottoms you’ll want. However, if you’ll be generating a lot of heat with your activity, you will want to go a bit lighter on the baselayer.  

Rain and snow will also factor into your choice.

Do you prefer the natural insulation of merino wool or the quick-drying properties of synthetic fabrics?

If you anticipate wet conditions, you may prefer a synthetic baselayer as it will dry more quickly. However, merino still insulates well even when wet, so if you’re only out for the day, merino can still be a comfortable choice. Extended trips may benefit from synthetics that will dry out more quickly, but merino will stay funk-free longer than synthetics, which tend to build up smells rather quickly. 


Care and maintenance tips

Proper care will keep your performance long underwear working season after season. Follow these guidelines to preserve fabric structure, wicking ability, odor-control, and warmth:

1. Dry completely before storage. After wear, allow the base layer to dry fully—preferably hung or spread flat—before folding or packing. Damp storage encourages odor-causing bacteria and fiber breakdown.

2. Wash on cold, gentle setting. Use cold water and a gentle cycle with mild detergent. This helps preserve stretch, fabric finishes, and color. Avoid hot water, which can degrade elastic fibers over time.

3. Choose line-drying when possible. Hanging or laying flat to dry prolongs garment life. If you must use a dryer, select a low-heat or air-dry setting. High heat can shrink or warp the fabric, reducing fit and performance.

4. Skip bleach and fabric softeners. Bleach weakens fibers and damages technical finishes; fabric softeners leave residue that blocks wicking and odor resistance. Instead, use a detergent formulated for technical wool or synthetic fabrics.

5. Remove stains and sweat buildup promptly. Sweat-soaked garments can develop odor or discoloration. Rinse and wash soon after use, especially if you’ve been on multi-day trips or layered heavily.

6. Store properly between uses. Fold or roll loosely and keep in a cool, dry place away from direct sunlight. Avoid compressing wool long underwear for extended periods, which can flatten natural loft.

7. Refresh performance annually. For wool base layers, consider re-treatment using fiber-safe wash-in products to restore water- and odor-resistance. For synthetics, inspect for thinning or pilling and replace if insulation or fit degrade.

By following these steps, you’ll protect the technical features—moisture management, odor control, and insulation—that make quality long underwear stand out.


Smartwool Intraknit

FAQ

  • Yes! Long underwear is perfect for warmer weather trips where the mornings/evenings may be cooler. This is especially true at high altitudes. You can wear your base layer until the temperatures warm up and then remove them when it’s comfortable. Base layers can also provide some level of sun protection while still remaining breathable, so pairing with shorts or a skirt for additional coverage can be a good option.

  • A good base layer fabric, such as merino or a highly breathable and wicking synthetic, will help manage heat. Choosing the right warmth level and appropriate outer layers is also key. Think about how you’ll feel after the first 15 minutes of your activity — you’ll probably warm up considerably as you move, so dress for that condition rather than being fully toasty to start out.  

  • Yes! Allow your long underwear to dry out if it gets wet or sweaty to keep odor down. Merino wool is particularly good at preventing odor buildup and can be worn many days in a row without smelling bad.

  • This is a personal choice, but most people will likely prefer to wear underwear with their long underwear. The fit of regular underwear may provide a tighter fit and better comfort and protection against chafing than long underwear alone. Additionally, the additional layer of regular underwear will help keep your long underwear fresher and extend the time between washings.  

  • Long underwear bottoms in a ¾ length cut are ideal skiing, since you don’t want extra bulk inside your ski boots.  Winning models we reviewed that have cropped length options: 

    Decide on your preference for merino vs synthetic and how heavy/warm is best for the conditions and locations you'll be skiing.

How we researched and tested

Some of the many ways we tested women’s long underwear bottoms.

Some of the many ways we tested women’s long underwear bottoms for fit, comfort, mobility, stretch, and quality waistbands.

We tested these base layers over 2 years of testing, mostly during winter in the Pacific Northwest. Activities included cold and rainy day hikes up to 30 miles in length, and snowshoe adventures and overnight hut trips and snowshoeing trips in the Gifford Pinchot and Mt. Hood National Forests, and even a winter summit of Mt St Helens and circumnavigation of Crater Lake in winter.

We also ventured out to the Trans-Catalina Trail in California to ring in the New Year and braved a frigid spring break packrafting trip in Utah. 

In all, I've been testing women's long underwear for nearly 2 years on everything from cold weather hikes after work to mountaineering ascents. 

This guide on women's long underwear is based on hundreds of hours of testing in cool and cold weather in Oregon, Washington, California, and Utah.


Kate Hoch Backpacker Outdoor Writer

About the author / Why you should trust us

I’ve been on the board of ALDHA-West (American Long Distance Hiking Association - West) (including most recently as President) most of the past decade. As part of our annual pre-backpacking season educational events (called “Rucks”), I’ve conducted many pack shakedowns and been a panelist on lightweight gear forums. I’ve shared my knowledge and expertise with hundreds of new backpackers. Running these events also keeps me on top of the newest available options for all kinds of backpacking gear.

You can read all of my articles on my author page or read more on my thru-hiking blog.