The Best Base Layers for Women of 2024-2025

The key to any successful outdoor excursion is staying warm and comfortable. Your layering system can make or break an experience, and the stack starts with the best base layers for women. Next-to-skin apparel is foundational for core winter sports, alpine adventures, and the shoulder seasons. Whether you’re hitting the slopes or walking the dog on a frigid day, quality base layers help to manage perspiration, body heat, and overall protection.

Base layers are made in various densities — lightweight, midweight, heavyweight — and each one provides a different degree of warmth and hand feel based on the fabric choice. Merino wool tends to be a top performer. Among our favorites are the medium-weight Smartwool Women’s Classic Thermal Merino Base Layer Crew and matching Bottoms, which provide middle-of-the-road warmth for moderately cold days at the ski area.

Yak wool and wool-synthetic blends also perform well in extra-cold environments. Compared to synthetics, wool has the bonus of holding warmth even when it’s wet. It’s the best for beating back odors during long periods of use, like multi-day hut trips. The higher the percentage of wool, the warmer a base layer will be, making this fiber superior for frigid climates. But synthetic fabrics have a lot to offer. They’re often more affordable, like the Helly Hansen LIFA Crew Base Layer, which you can snag for less than $50. They usually deliver more durability and elasticity. And while you tend to give up some odor control, synthetics are the fastest-drying textiles. Some of these fabrics are a top choice for aerobic activities where you’ll work up a sweat, thanks to their quick-drying properties.

Since this field-tested guide was first published in 2019, our team has continued to thoroughly test ladies’ base layers in a range of weather conditions and climates. For many women, pulling on a well-constructed merino wool base layer hits the mark for most wintertime activities. To learn about base layer designs, jump down to the Buyer’s Guide in the lower half of this article, which spotlights Price & Value. Also, have a look at our Comparison Chart to steer your decision-making.

Editor’s Note: We updated our Base Layers for Women buyer’s guide on September 15, 2024, to include field testing images, history, and context, plus the Icebreaker Women’s 260 ZoneKnit Long Sleeve Crewe Thermal Top and Thermal Leggings.

The Best Base Layers for Women of 2024-2025

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Base Layers for Women Comparison Table

Scroll to the right to view all of the columns: Price, Weight, Fabric, Thermal Category.

Base Layers for Women	Price	Weight	Fabric	Thermal Category
Smartwool Women’s Classic Thermal Merino Base Layer Crew & Bottom	$115	218 g (top), 208 g (bottom)	100% merino wool	Midweight
Helly Hansen Women’s HH LIFA Long-sleeve Crew Base Layer	$45	108 g	100% polypropylene (Lifa)	Lightweight
REI Co-op Lightweight Base Layer Tights Women’s Plus Sizes & Top	$40	218 g (top), 208 g (bottom)	92% polyester, 8% spandex	Lightweight
Kari Traa Rose Half Zip Baselayer Top & Pants	$120, $110	Unavailable	100% merino wool	Midweight
Ortovox 185 Rock’N’Wool Long Sleeve & Short Pants	$110, $100	142 g (bottom), 164 g (top)	100% merino wool	Lightweight
Le Bent Women’s Core Lightweight Crew Base Layer	$105	200 g	66.5% rayon from bamboo, 28.5% merino wool, 5% elastane	Lightweight
Wild Rye Olivia Onesie	$249	510 g	100% merino wool	Midweight
Halfdays Hallie Midweight Merino Legging	$95	9.59 g	51% merino wool, 40% bamboo viscose, 9% polyamide	Midweight
Le Bent Women’s Feathertop Ultralight Hooded Long Sleeve Tee	$160	125 g	Proprietary Nuyarn merino wool and raw bamboo blend	Lightweight
Voormi Women’s Baselayer Bottoms Full Length & Crew	$119	195 g	Unavailable: Proprietary wool and synthetic fiber blend	Midweight
Icebreaker 260 ZoneKnit Long Sleeve Crewe Thermal Top & Thermal Leggings	$165	201 g (top), 190 g (bottom)	100% merino wool	Midweight
Black Diamond Women’s Solution 150 Merino Baselayer Crew	$135	146 g	78% merino wool, 22% polyester	Lightweight
First Lite Kiln Hoody & Long Janes	$130, $95	425 g (top), 227 g (bottom)	95% merino wool, 5% spandex	Midweight

How We Tested the Best Base Layers for Women

The GearJunkie product testing team includes a range of skiers and snowboarders from intermediate to expert who explore ski areas around the world, venture into the backcountry, skin uphill at the resort, après in the parking lot, and enjoy Nordic trails. We don’t shy away from winter runs and embrace the mantra “there’s no bad weather — only bad clothing,” when it comes to playing outside in the depths of winter. 

Our team includes avid hunters and folks who live in wintry, cold, mountainous locations from Bozeman, Montana, to Crested Butte, Colorado. We backpack, alpine climb, hunt, and track elk in the fall shoulder season. In the spring, we go ice climbing and mountaineering. The first iteration of this guide was authored by then-contractor Morgan Tilton, in 2019, following extensive field tests. To narrow down the top 10 base layers on the market, she heavily researched, coordinated, and dispersed base layers to a diverse group of outdoor professionals and athletes nationwide, who reported detailed findings in addition to Tilton’s personal field tests in Colorado. Since then, this guide has evolved through eight published updates, as of September 2024. Today, the guide highlights 14 tested product collections that represent the best of the best base layers for women.

Our Expert Testers

GearJunkie Senior Editor Morgan Tilton specializes in snowsports and manages the majority of the publication’s winter guides including Base Layers for Women, which has occupied her editing desk since 2022. She was born and raised in Colorado’s San Juan Mountains, where she learned to slide on snow at age 4, in her backyard: Telluride Ski Resort. Today, she lives and plays in Crested Butte, Colorado, from the slopes to the backcountry on two planks and one, human-powered and by motor. She’s worn a ton of base layers over the past three decades — and the ladies’ designs really do keep getting better.

She’s been an outdoor industry journalist covering winter gear for more than a decade. That includes reporting at 16 industry trade shows, publishing the Outdoor Retailer Daily and Snow Show Daily, and serving as Snowboard Editor at Teton Gravity Research. Bolstering remote exploration, she is Wilderness First Responder certified and has completed the recreational-tier avalanche training courses from the American Institute for Avalanche Research and Education. 

Contributing testers for this guide include former GearJunkie editors: skier and ice climber Mary Murphy, hunter Nicole Qualtieri, and packrafting homesteader Mallory Paige. Our field testers have also included snowboarder Julia Spadaro, skier Kylie Mohr, American Mountain Guides Association (AMGA) certified rock guide Karin Pocock, rancher and wildlife photographer Constance Mahoney, as well as a sugar beet harvester and ski patrol tail guide.

Our Testing Grounds

Today, GearJunkie Senior Editor Morgan Tilton lives in Crested Butte, Colorado, with the Elk Mountains at her doorstep. There, she skis, snowboards, snowmobiles, and shovels unbelievable amounts. She’s also tested base layers on the blustery slopes of Eldora Mountain, foggy and icy days at Utah’s Snowbasin Resort, ample powder rounds at Telluride Ski Resort, and throughout the backcountry of the Elk and San Juan Mountains. The majority of her inbounds gear testing takes place at Crested Butte Mountain Resort, a few miles away from her shoveling habitat. 

These second-skins were used hiking, camping, rock climbing, hunting, ranching, farming, trail running, backcountry touring, skiing, snowboarding, and snowball fighting. We adventured across North Dakota farmlands, up cracks in Utah’s Indian Creek, and throughout Colorado’s high-elevation peaks and limestone walls. Temperatures stretched from splitting cold at sunrise in the glades to scorching under the sun during fieldwork. 

In spring 2022 and 2023, Crested Butte Mountain Resort was the host location for the official GearJunkie Ski and Snowboard week, where our team meets to test upcoming hardgoods and softgoods.

Our Testing Process

Our team field tests all of the women’s base layers that are included in this guide. While the Smartwool and REI base layers constructed for extended sizes have not yet been field tested, we are onboarding plus-size testers for the winter of 2024-2025. To start, we have tested those products in alternative size runs, attended plus-size apparel panel presentations, interviewed the plus-size base layer designers, and are confident in our conclusions.

While she teams up with many gear testers, Tilton puts goods to the grindstone between keyboard blocks. To date in 2024, Tilton has packed in 62 days and 216 hours of testing women’s base layers. From January to December 2023, Tilton tested women’s base layers across 68 days and 198 hours of recreation. Her outings took place in the frontcountry and backcountry including bebopping via snowmobile. Those days entailed blizzards, sub-zero temps, harsh wind, heavy and wet snow, plenty of perspiration, and sunshine. That metric excludes running to get the mail (with base layers on under jeans) and the intense daily shoveling responsibilities at her home in Crested Butte, when she often pulls on bibs.

One of our testers is environmental journalist Kylie Mohr, who spends time running and skiing up and down the mountains of Montana in various blustery conditions. She wore these base layers in and out-of-bounds to see what most kept her warm and dry. Avid snowboarder and Utahan Julia Spadaro spends her winters snowboarding at the resort and splitboarding in the backcountry, as well as hiking in the shoulder seasons. She tests women’s base layers throughout all of her adventures and delivers knowledgeable reports on what she does and doesn’t like.

Testing Metrics

Throughout our field tests and personal experience, we determine the most competitive women’s base layers based on a variety of metrics including quality, comfort, fit, longevity, and value. We take a close look at each product’s warmth, breathability, wicking and drying capability, material, elasticity, stretch, weight, density, seams, hems, cut, hand feel, and style.

We also consider the most innovative, sustainable, legacy, award-winning, and popular designs on the shelf today. Hands down, these women’s base layers serve a wide range of athletes, applications, and budgets.

Buyer’s Guide: How to Choose the Best Women’s Base Layers

In our guide, we focus on the best options for cold weather and the winter season, which are often long-sleeve tops and ankle-length bottoms.

Technically, women’s base layers feature a range of designs including tank, long-sleeve, and short-sleeve tops, as well as ankle-length or capri pants. Some tops feature a hood, partial zipper, or thumbholes. Others are tailored with a crew collar, mock neck, or turtleneck. While most against-skin layers lack pockets, we’ve seen leggings popping up with a spacious side pocket, which is useful to stash a phone, especially post-activity when you pull off your snow pants.

Two fundamental umbrellas will help you decide which women’s base layers to buy:

• You’ll want to consider how cold the climate is where you play outside. The colder the zone, the more you’ll want to consider a wool-based blend, higher density fabric, and heavier fabric weight.
• The second variable is how active you’ll be while you’re wearing that apparel. During exercise, like shoveling or going on a winter run, your body is generating heat that would necessitate a more breathable, less density, low-weight top and bottom.

If you plan on being physically active in above-freezing but cool weather, we recommend a synthetic blend. If you’ll be rounding out winter days in a below-freezing climate, wool can be your greatest companion for warmth. Other factors can influence the best base layer choice including your body’s circulation, skin sensitivity to fibers (like wool), and the layers you put on top.

Layering System 

Your alarm goes off. Don’t snooze: It’s time to get up and dressed for cold weather fun. Your layers will work in a tiered system:

• Base Layer: Next to skin to wick sweat
• Midlayer: Adds warmth to retain body temperature
• Outer Layer: Protection from the elements, repels precipitation, blocks wind; insulated outer layers increase warmth

First, put on your underwear and socks. They better be wool or a synthetic blend — not cotton. Your warm, dry epidermis will thank you. Your base layers go on next.

Base Layer

Add your base layer top, bottom, or onesie. If your bottoms are long, make sure they go over your socks. Unless you like your socks on the outside of your bottoms — that’s personal preference. If your bottoms are mid-shin length, like some compressive performance options, adjust your socks and fabric, so there aren’t any overlapping, uneven points that could rub or chafe. 

Midlayer

Now, it’s time to slip on your midlayer top and bottom, depending on the day’s activity. 

Going skiing in bounds? Reach for a streamlined fleece that still allows full range of motion. Hanging out at the campsite? Pull on a bulky deep-pile sherpa fleece.

Your activity will dictate what appropriate midlayers to add on the bottom. Maybe you’ll pull on a fleece or insulated puffy pants for extra warmth below workwear trousers or snow bibs.  

Outer Layer

Headed to the backcountry? Wear a comfy insulated jacket on the way to the trailhead then strip down to your baselayer or midlayer to start, given you’ll quickly warm up from exertion in the cold temps. Running in a breeze on an otherwise warm afternoon? Go for a softshell with no insulation.

If we’re resort skiing in below freezing temps, and we run cold, we’ll often do this trio: an uninsulated ski shell over both a fleece and puffy jacket. Insulated jacket wearers will likely find they don’t need all three. 

An ideal layering system is all about learning what works for you and how many layers you need to stay warm and dry.

Fabric Blends

The fabric blends of women’s base layers include wool, synthetic, or a blend of the two. Within those fabrics, there are various densities from lightweight to midweight or heavyweight.

Wool

We love wool. It regulates temperature really well and provides warmth when it’s damp or wet. It’s evolved to be much more comfortable against the skin and resists odors like a champ. The warmth to weight ratio is high, packing a punch in a fairly light package. It’s an ideal choice for low-intensity outdoor activities like ice fishing or spectating a hockey game. Among our top base layer choices is the Smartwool Women’s Classic Thermal Merino Base Layer Crew and Smartwool Women’s Classic Thermal Merino Base Layer Bottom, a 100% merino wool collection.

That said, 100% merino wool tends to be less stout than synthetics, wears holes more quickly, and can get baggy throughout use. If you have sensitive skin, even the smoothest 100% merino wool might feel a tad less than cloud-like next to the skin. Wool gets heavier when it’s wet and doesn’t dry as fast as synthetics. Depending on your preference, activity level, and the weather conditions, you might prefer a wool blend or straight synthetic materials.

Wool can cost more than its counterparts. Beyond Merino-sourced wool, we have tested base layers with wool from yaks, which was a premium thread, extremely soft, and super insulating.

Synthetic

An alternative to wool is a synthetic fabric, which is typically a blend that includes polyester plus elastane or spandex for rebound, form, and long-lasting use. Some synthetic fabrics are proprietary to a brand with treatments that enhance their odor-fighting ability and moisture-wicking prowess — the qualities that occur naturally in wool.

Synthetic blends do not offer as much warmth and overall temperature regulation that wool provides. Because they don’t absorb as much moisture and they dry fast, they’re a great choice for high-intensity activities that produce a lot of perspiration without long moments of standstill, like during a hunt, when a chill could set in.

These fibers can work really well for people with sensitive skin, especially for exercise use and the bonus of greater durability, stretch, and elasticity. Also, synthetics typically cost less than wool. One of our favorite synthetic options is the REI Co-op Lightweight Base Layer Tights Women’s Plus Sizes, at a whopping $40.

One drawback: Odor-intense days are not typically covered up well by this fiber in its naked form.

Wool-Synthetic Blend

Many folks find a fair balance of managing heat and chill, sweat absorption, and covering up odors in a design that weaves together both wool and synthetic fibers. Adding synthetics to blends can enhance the strength and overall lifespan of wool apparel.

One of our all-time favorites for wearing from the skintrack to happy hour is the Le Bent Women’s Core Lightweight Crew Base Layer, which includes 5% elastane and maintains a nice shape throughout long days.

Weight Class or Thermal Category: Lightweight, Midweight, Heavyweight

When you shop for women’s base layers, the products are categorized by three weight zones, which generally refers to how heavy or light the layer is and feels. The weight class is influenced by the fabric density and thickness, which changes the activities that layer is compatible with.

Here, we listed the weight class in each products Specs — under Thermal Category — which is based on our test results.

Weight class isn’t directly correlated to warmth. A lightweight pure-wool top can bounce back a ton of body heat. It will be easier to move in, less dense, and more breathable than a midweight or heavyweight wool design.

While everyone’s circulation and preferences are different, here’s a general start point for deciphering a weight class based on activity level and outdoor temperature:

Sedentary:

• 25-32+ degrees: Lightweight, wool
• 15-25 degrees: Midweight, wool

Active:

• 25-32+ degrees: Lightweight, synthetic
• 15-25 degrees: Lightweight, wool-synthetic

Lightweight

If you’re running hardpack snow trails, snowshoeing, skate skiing, or doing uphill ski workouts in 30-degree temps, a lightweight base layer top or bottom should do the trick, as long as there’s no wind chill.

Lightweight layers dump heat really well. These could be a good piece for warmer spring laps at the ski resort. But sitting idle on lift rides in cold temps typically calls for a warmer midweight base layer. One of our favorite lightweight synthetics is the Helly Hansen Women’s HH LIFA Long-Sleeve Crew Base Layer, and a lightweight wool blend that’s super soft and versatile is the Le Bent Women’s Core Lightweight Crew Base Layer.

Midweight

Not too airy and not too stuffy, the midweight base layer is optimal for wintry days skiing and riding at the resort. It’s a good choice for snowmobiling, when pulling the throttle can pack windchill at high speeds.

That said, for intense heat-building activities like huge ski or splitboard tours or snowshoeing, a midweight layer might be too much unless the temps are colder, like 15 degrees or less.

Squarely midweight, we love the Smartwool Women’s Classic Thermal Merino Base Layer Crew and Smartwool Women’s Classic Thermal Merino Base Layer Bottom as a well-rounded kit for cold or below-freezing temps and days at the ski resort.

Heavyweight

When we’re talking extreme temperatures — 15 degrees with windchill to well below freezing — then your best bet is a heavy-set base layer, especially for ski resort laps when you are sedentary on the way up.

Other more passive outdoor activities could include ice fishing, sailing, hunting, spectating events, hanging at base camp during a mountaineering expedition, or snowmobiling groomed trails, especially if sightseeing stops are frequent.

We don’t currently have any bulky heavyweight options in our guide. Many of our 100% wool midweight selects can be layered beneath a midlayer fleece and down jacket for super cold conditions, and we prefer that versatility. The Kari Traa Rose Half Zip Baselayer Top and Kari Traa Rose High Waisted Baselayer Pants feel lean but are packed with heat. These are our go-to on a 0-degree day at the ski resort. We don’t usually like wearing these while we ski tour to avoid an oven-effect.

Fabric Density

A standard unit for measuring fabric density is gsm (grams per square meter). The higher the gsm, the denser and warmer that textile will be. A fluid-feeling blouse might be as low as 50-100 gsm, while denim reaches into the 340-450 gsm range.

Some women’s base layers do not weigh much but have a dense fabric or high gsm. Therefore, they swing a high warmth-to-weight ratio, such as the Kari Traa Rose High Waisted Baselayer Pants with 240 gsm. After testing, we associated that legging as midweight, thanks to the relatively low density yet high heat punch.

Rather than adding gsm labels to our product reviews here, we shared the general weight class — lightweight, midweight, and heavyweight — which is more ubiquitously used across brands. Our listed weight class is based on our test results. That said, understanding how to interpret the density of a base layer is a very useful tool.

Here’s a broad rule of thumb for gsm:

• Ultralight base layers: >150 gsm
• Lightweight base layers: 150-195 gsm
• Midweight base layers: 195-250 gsm
• Heavyweight base layers: 250-320 gsm

You’ll want to match your physical exertion or circulation to the fabric density. If you plan to do high cardio activity, choose a base layer design with a lower density.

If you plan to be more sedentary — such as waiting in long ski lift lines during a blizzard, ice fishing, watching a hockey game, or running errands — opt for a higher gsm. A higher fabric density is also a good option for folks who have poor circulation or tend to get chilled during winter activities.

Breathability

In addition to trapping heat, it’s important for your base layer to breathe well and efficiently wick moisture. Freezing sweat will make you colder faster. Generally, the lighter or less dense a design is, the more breathable it will be. Merino wool is also more breathable than synthetics. Base layers can be made with a blend of materials that place more breathable textiles in high-heat zones.

When we’re talking about engineering, we can’t forget about the Icebreaker 260 ZoneKnit Long Sleeve Crewe Thermal Top and Icebreaker 260 ZoneKnit Thermal Leggings, which has a breathable mesh-like merino wool layer in all the important places — the lower legs, behind the knees, across the back and upper glutes, under the arms — so sweat can’t ruin the day. The Kari Traa Rose Half Zip Baselayer Top uses a lighter density merino wool under the arms and along the sides, which feels more breathable.

In general, we found that the Smartwool Women’s Classic Thermal Merino Base Layer Crew is a warm winter layer that breathes pretty well. It’s our top pick for the dead of winter but also for alpine pursuits in fall and winter. The Voormi Women’s Baselayer Bottoms Full Length and Long Sleeve Baselayer Crew also breathe rather well, and repel water, keeping us dry after sweaty ascents and snowmobile rips.

If you know you’re going to be busting it uphill on a warm day in the springtime, look for an even lighter and more breathable layer. Something like the Helly Hansen Women’s HH LIFA Long-sleeve Crew Base Layer or REI Co-op Lightweight Base Layer Tights Women’s Plus Sizes and Top will be a key part of your layering system.

Odor Prevention

If you’re packing minimally for multiday use, like a hut-to-hut ski, merino wool does wonders with hiding odors. Generally, synthetic materials don’t champion coating stench as well as this natural fiber. Merino wool wicks sweat away from your body, allowing it to evaporate rather than sink into your clothes. Wool fibers absorb nearly twice as much water vapor as cotton and 30 times as much as polyester. The structure of wool binds with odors, playing keep away from bacteria. 

While polyester — a primary thread in synthetics — isn’t naturally odor-resistant, garments can be treated to mimic some of the same benefits as wool. Silver-based compounds and triclosan and triclocarban treatments are toxic to odor-causing bacteria, keeping the nose-pinch at bay. Keep in mind, these treatments’ effectiveness could decrease over time as a garment is washed. 

Sun Protection

Many base layers hidden beneath midlayers or outerwear jackets will never see the light of day. But others, especially lightweight ones geared for year-round or springtime use, will. That’s where sun protection is a nice added feature.

The REI Co-op Lightweight Base Layer Long-Sleeve Crew Top Women’s Plus Sizes boasts a UPF rating of 50+, as does the Le Bent Women’s Feathertop Ultralight Hooded Long Sleeve Tee. But Le Bent’s design also offers a hood, so you’re getting additional protection of your ears, plus the back of the neck. The Le Bent Women’s Core Lightweight Crew Base Layer likewise sports a UV 50+ tag.

Durability

Thermal layers are an investment, so it makes sense that you want them to last. They’re also only one piece of a long list of gear that’s needed to venture out in the winter.

Synthetic layers are often more steadfast than wool but can cause more trouble with retaining odors. Manufacturers often add synthetic fibers to their wool apparel to help increase the overall timestamp. Wool is naturally warmer and odor-fighting but tends to be more fragile. You’ll want to take care putting them on, as well as how you wash and dry them.

Hands down, the most durable construction of any of these base layers is that of the Voormi Women’s Baselayer Bottoms Full Length and Voormi Women’s Long Sleeve Baselayer Crew. In the brand’s proprietary process, in-house seamsters create their Dual Surface material, a precision-blended wool technology with a lean interior layer of fine micron-wool plus a portion of polyester and nylon. After several years of use, we don’t see holes surfacing in these layers any time soon.

Comfort & Fit

Most base layers offer a degree of flexibility and are soft or nonabrasive, which supports overall comfort and fit. But some base layers we’ve tested in the past have had a tighter compression fit for optimal athletic performance. One of the more challenging base layers to pull on is the Voormi Women’s Baselayer Bottoms Full Length and Voormi Women’s Long Sleeve Baselayer Crew, especially at the seams. However, we love how tough and time-withstanding this design is. The next most close-fitting design in our guide is the Halfdays Hallie Midweight Merino Legging, but it does offer ample stretch, even along the seams.

When we test base layers, we’re looking for tops that provide enough range of motion across the chest and shoulders, as well as when lunging or squatting. The seams need to be smooth or flat, and the gusset needs to be well-constructed, so we don’t feel any jabs or experience chafing. The construction is very smooth across the Ortovox 185 Rock’N’Wool Short Pants and Ortovox 185 Rock’N’Wool Long Sleeve.

We care about the silhouette, because we prefer arms that at least cover our wrists and torso lengths that don’t allow the lower back to be exposed to the elements.

Pant Length 

Most base layer pants reach down to your ankle but some capri styles hit below the knee, near the shin bone. We like a cropped length for easy layering with our socks and ski boots. The Ortovox 185 Rock’N’Wool Short Pants reach the knee and eliminate the need to layer our pants over socks.

Bottoms that reach closer to your feet are usually tapered and snug, so they can be easily tucked in when necessary. But there’s usually enough pliability in the fabric to slide your winter socks underneath, if you prefer. 

Onesie & Drop Seat

Sometimes a separate top and bottom just won’t cut it. We’re thinking about those best-of-the-season powder days where a gap in base layer coverage could lead to snow where the sun doesn’t shine. Base layers with a seamless connection are a rare, but increasingly popular, option in the base layer lineup. They’re called onesies or one-pieces that include a top and a bottom sewed together. Think wet suits and footie pajamas. 

Leading the charge is the Wild Rye Olivia Onesie base layer. Wearers are treated with head-to-toe merino wool. A hood adds coziness, and fun patterns like chunky yellow florals stand out against your friends’ all-black arsenal. A half-zip helps regulate temperature on this warm, 230 gsm style.

The best feature on a onesie is a rear zip, or drop seat, for easy release. The drop seat is a removable backside flap, usually with zippers that span hip to hip above your booty, to make using the bathroom easier. No one likes having to get totally naked to answer nature’s call. Brr! Though we haven’t tested this one yet, the Backcountry Airblaster Merino Ninja Suit is another onesie option on the market.  

Hoods & Collars 

Hoods are fairly rare on base layer tops. After all, how many hoods do you really want to be wearing at once? Hoods can sometimes add bulk around the neck and head area, especially if your base layer, fleece, puffy, and shell all have one.

But some of our favorite base layers rock a hood, like the First Lite Kiln Hoody and the Le Bent Women’s Feathertop Ultralight Hooded Long Sleeve Tee, which is superb for spring mountaineering and sunny, warm ski tours. It can be nice to have a slender hood around your neck to layer under a helmet or hat, which can further block the sun and wind. 

Certain base layers have a scoop neck while others have collars with a quarter- or half-zipper at the chest and décolletage. We like a mock turtleneck cut to fully protect our neck and chest without the restriction of a full turtleneck. The Kari Traa Rose Half Zip Baselayer Top combines a half-zip with a mock turtleneck.

Sleeve Cuffs & Thumbholes

On long-sleeve base layers, the cuff is a piece of fabric that demarcates the garment’s edge, at the wrist. It’s sewn on to help prevent fraying and increase comfort. The lengths of base layer sleeves, as well as the depth and elasticity of their cuffs can greatly vary. Longer sleeves can reach the knuckles, covering the backs of the hands and palms. Others end at the wrist, before extending over the hand.

Thumbholes, also known as thumb loops, are technical slits in long cuffs, which the thumbs can sit in. It’s like a seatbelt on a cocoon that helps to keep your hands and wrists warm. Adding thumb loops helps the sleeve stay drawn across the hand. That way, the fabric won’t bunch up when you pull on your outer jacket. The precise width and placement of the loop that goes around your thumb varies by brand and design. A handful of thumbhole designs are simple elastic bands. But many thumbhole designs are created with a wide piece of fabric and include seams.

Sometimes, thumbholes can be tedious to slide into, cumbersome under ski gloves, or incompatible with a watch. Some ski jacket designs have built-in wrist gaiters with thumbholes, which leads a traffic jam around your wrist — and at worst, poorer circulation — if your base layer top also has thumbholes.

We especially like the thumbholes on the Black Diamond Women’s Solution 150 Merino Baselayer Crew. They are stretchy enough to be comfortable while wearing them for back-to-back hours. The Wild Rye Olivia Onesie thumbholes include a beefy cuff, so they’re cozy to wear indoors but outside, we pull them back to put on gloves. We found the thumbholes of the Voormi Women’s Long Sleeve Baselayer Crew to be too small and restrictive, greatly due to the lack of stretch in the seams. The First Lite Kiln Hoody thumbholes are really easy to pull on and off, as are the ones on the Icebreaker 260 ZoneKnit Long Sleeve Crewe Thermal Top.

Sustainability 

When it comes to sustainability, buying new gear isn’t as environmentally friendly as having a closet swap with friends or finding scores at the thrift store. But conscious consumers can shop with Mother Nature and humanity in mind.

Finding sustainable base layers includes recycled materials, ethically sourced material, and responsible manufacturing facilities like those that don’t dump harmful toxins into nearby waterways and pay their employees a livable wage. 

Certified Materials

Some women’s base layers are certified by Bluesign, an organization that works to keep chemicals out of the supply chain for the health of humans, wildlife, natural resources, and the earth. Approved factories meet standards for pollution control and worker safety. Products reach those standards partially or as a whole. The Helly Hansen Women’s HH LIFA Long-sleeve Crew Base Layer is Bluesign-approved.

The Le Bent Women’s Feathertop Ultralight Hooded Long Sleeve Tee feature Nuyarn fibers, which set an impressive benchmark: Responsible Wool Standard Certified, Bluesign-certified, Oeko-Tex Standard 100, and the Global Organic Textile Standard.

Similarly, the REI Co-op Lightweight Base Layer Tights Women’s Plus Sizes and Top is made in a Fair Trade certified factory. That certification means the factory meets safe working conditions as well as environmental protections and that the supply chain is transparent. Ortovox gives two stamps to its Ortovox 185 Rock’N’Wool Short Pants and Ortovox 185 Rock’N’Wool Long Sleeve: validation from the Fair Wear Foundation, for equitable working conditions, and climate neutral.

Responsibly Sourced or Recycled Materials

We’ve seen the brand Daehlie do well with material sourcing for products, selecting fiber from fast-growing eucalyptus trees on a farm that’s certified by the Forest Stewardship Council.

Using textiles sourced from recycled materials, such as old plastics, is one way that companies reduce waste and demand for petroleum-based products. Materials can be partially or fully recycled, like the recycled polyester in the Patagonia Capilene line. 

Smartwool argues that wool is an inherently responsible choice: It’s not plastic, and it breaks down in water and soil. The brand’s wool is ZQ-certified by a New Zealand-based group that sets standards for animal welfare, social responsibility, and environmental sustainability. You’ll see this wool in the Smartwool Women’s Classic Thermal Merino Base Layer Crew and Bottom, as well as all of the brand’s base layer offerings. 

Price & Value

Our favorite women’s base layers run from $40 to $229. That includes options for the budget-conscious shopper and the athlete wanting to splurge on a technical textile.

Budget

The most economic choices have a basic construction, fit, and work well. The blends are synthetic, not as complex or articulated, and typically do not include wool. You won’t find pockets in the leggings. The weight category, thermal power, and fabric density is usually lower. You probably won’t see a synthetic fabric coated to block odors.

But if you need a basic base layer for sledding and ski hill laps, these certainly get the job done. On this lower end, there’s the REI Co-op Lightweight Base Layer Tights Women’s Plus Sizes and Long-Sleeve Crew Top, each for $40, and the Helly Hansen Women’s HH LIFA Long-Sleeve Crew Base Layer at $45.

Mid-Tier

In the “100 bucks, give or take” shelf, you’ll see a bump up in the complexity of the textiles, how they’re constructed, as well as a slightly higher quality and softer feel of materials. Merino wool enters the game.

These are among our favorite base layers out there. We’ve got the Smartwool Women’s Classic Thermal Merino Base Layer Crew and Bottom for $115. There’s also the Le Bent Women’s Core Lightweight Crew Base Layer for $105. The Ortovox 185 Rock’N’Wool Long Sleeve and matching Short Pants are tagged at $110-$100. Despite being super cohesive and inherently water resistant, the Voormi Women’s Baselayer Bottoms Full Length and Long Sleeve Baselayer Crew sits at $119.

Premium

While the Wild Rye Olivia Onesie is available at $249, it’s close to a mid-tier price point when you consider the price of a bottom and a top base layer that’s woven together in a single package. This stylish one-piece is the most technical to create and includes a drop seat for bathroom breaks.

But those tad higher price points include the Kari Traa Rose Half Zip Baselayer Top for $120 (the Kari Traa Rose High Waisted Baselayer Pants are labeled at $110), which is woven with high-quality wool from merino sheep, has an articulated cut and the patterns are stylish. They look beautiful. The Black Diamond Women’s Solution 150 Merino Baselayer Crew is available at $135 a pop. The First Lite Kiln Hoody is $130, while the sister piece, the First Lite Kiln Long Janes, is lower at $95, for a good balance.

The most premium option in our guide is the Icebreaker 260 ZoneKnit Long Sleeve Crewe Thermal Top ($165) and Icebreaker 260 ZoneKnit Thermal Leggings ($165), which are strategically body-mapped for highly breathable zones in an otherwise heat-loaded wool package.

Frequently Asked Questions