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The 20 Best Base Layers to Keep You Warm All Winter Long

Ditch the cotton long johns – these quality base layers are made from everything from merino to bamboo.

2 people getting ready to go hit a ski hill Courtesy
AJ Powell

By Hayley Helms, Tanner Bowden, AJ Powell, and Meg Lappe

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Base layers need to do three things in order to perform well in the outdoors. They need to keep you warm through insulation, they need to breathe well during aerobic activities, and they need to wick moisture away from your body and allow it to evaporate. While your good ol’ waffle-style long johns might be comfortable and cozy near the fire, they no longer cut the mustard when it comes to modern needs. Merino wool, synthetic materials and a host of alternatives are better designed to accomplish all three objectives well, and they can be relied upon to do the job when you need them most.

Products in the Guide

Types of Baselayers

Baselayers traditionally fall into three separate categories: light, medium and heavyweight. Each weight type is designed for specific conditions and sometimes activities. Retailers or manufacturers will typically provide the insulation weight and sometimes the g/m2 spec (the grams-per-square-meter measurement of the fabric), which measures how thick and heavy a material is. It’s important to note that there is no standardized unit of measurement for the weight of baselayers: each manufacturer formulates its own scale, so it’s important to read product descriptions and recommended uses — and to experiment a bit — to find which weight is right for you.

Materials

There are a few primary types of materials you’ll find used in baselayers: merino wool, synthetics and alternative materials like bamboo. Merino wool is by far the most popular: it’s the gold standard in base-layer materials. Its fibers are naturally antimicrobial, so they fight the stench that occurs after a few days on the trail, and the fabric is great at regulating temperature, making it usable in multiple environments. It also breathes well and wicks moisture away from your body to keep you dry.

Synthetic materials pack a big punch at a low price point. While they tend to pick up a stench easier than other materials, they do the trick of keeping you warm and wicking moisture away quickly. An easy solve for this is a blend of all-natural and synthetic materials (like the Patagonia picks in here). They’re also highly breathable, and after purchasing, they leave a little bit of extra cash in your wallet for something like a nice pair of hiking boots or new goggles.

Onesies are a great way to keep warm on super-cold days. Even if the material is a lighter weight than you would typically wear on a cold day, the one-piece construction retains heat better than a top/bottom combo, so it’ll keep you plenty warm. As a bonus, they make great Halloween costumes.

And finally, let’s talk alternative materials. Recently, many manufacturers have started making base layers out of alternative materials. The below examples include bamboo wovens, yak wool and silk. They offer similar performance to merino and synthetic materials but also offer other benefits, such as sustainability (as with bamboo fiber).

When Should I Wear Baselayers?

We wear our baselayers for a number of activities: while we ski and snowboard, hike through alpine terrain, for post-activity campsite hangs (under our more casual pants/ shell and paired with beanies and gloves) and for hunting. Basically, any outdoor activity where temperature regulation is a must, and heat retention is required, we’ve got baselayers on.

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Merino Wool

Natural fibers that shake the scratchy wool stigma.

Fjallraven Bergtagen Woolmesh Sweater

  • Materials: 80% wool, 20% polyamide, 52% wool, 35% polyester, 13% polyamide, 95% wool, 5% elastane

Fjallraven’s technical baselayer top is a mountaineering-specific blend of merino wool and synthetics: it provides both warmth and stretch and has a body-mapped design built to dump and alternatively retain heat in all the right places.

Fjallraven Bergtagen Thinwool Long Johns

  • Materials: 100% merino wool

These light, soft, thin long-john style baselayer tights from Fjallraven are 100-percent merino wool and were designed to wick moisture away and insulate in both wet and dry environments. Naturally anti-microbial and anti-odor, these tights are great for multi-day trips where packing has to stay at a minimum.

Smartwool Merino 150 Long-Sleeve Baselayer

  • Materials: 87% merino wool, 13% nylon

Smartwool has set the bar for high-quality, affordable baselayers that perform with the best of them. The Merino 150 Long Sleeve Baselayer is a great everyday piece that can insulate in all but the most extreme temperatures.

Smartwool Classic All-Season Merino Base Layer Bottom

  • Materials: Nylon and merino wool blend

This classic pair of merino baselayer tights use a blend of nylon and merino wool to increase durability and stretch without sacrificing warmth. 100-percent merino wool is still next to skin, so the soft and cozy feeling isn’t sacrificed by the material blend.

Icebreaker Merino 175 Everyday Long Sleeve Half Zip

  • Materials: 100% merino wool

Icebreaker’s half-zip thermal baselayer top is great for environments where weather can shift on a dime, and the partial-zip design of this top is great for dumping heat when temps rise. On Icebreaker’s weight scale this long sleeve is ranked as ultralight, so be aware that it’s best used for high-intensity aerobic activities or warmer winter environments.

Icebreaker BodyfitZone Merino 260 Zone Thermal Leggings

  • Materials: Body: 97% Merino Wool, 3% Elastane, Panels: 100% Merino Wool, Eyelet: 98% Merino Wool, 1% Elastane, 1% Nylon

These midweight Icebreaker tights have been body-mapped to locate the specific zones of your lower half that need a little more warmth and those that can benefit from thinner, more breathable fabric.

Synthetics

High performance at an affordable price point.

Corbeaux Respire Long Sleeve

  • Materials: bluesign-certified 88% Recycled Polyester / 7% Spandex / 5% Polyester

Built by hand in Saint Paul, MN, this baselayer top is well-equipped to handle a variety of outdoor activities. An ultra-lightweight, 149gsm blend of recycled polyester, this fabric is 4-way stretch, bluesign-certified and has a naturally occurring UPF 15 sun protection (although we’d still put a layer of sunscreen on just in case).

Corbeaux TJ Pant

  • Materials: bluesign-certified 88% Recycled Polyester / 7% Spandex / 5% Polyester

A three-season baselayer pant meant for spring, summer and fall, these may be a tad too thin for winter explorations, but for the rest of the year, the recycled poly/ spandex/ nylon blend holds its own against cooler temps.

Patagonia Capilene Air Crew

  • Materials: 5.6-oz (190-g) 51% responsibly sourced merino wool/49% recycled polyester seamless zigzag knit comprised of 18.5-micron-gauge lofted wool

Patagonia’s Capilene line is well-known for its comfort and performance capabilities, and the Air Crew is a continuation of that: built with a blend of 51-percent responsibly sourced merino wool and 49-percent recycled polyester, it wicks moisture, repels odor and dries faster than you can say “Patagucci.”

Patagonia Capilene Air Bottoms

  • Materials: 5.6-oz (190-g) 51% responsibly sourced merino wool/49% recycled polyester seamless zigzag knit comprised of 18.5-micron-gauge lofted wool

Much like their long sleeve counterpart, the Patagonia Air Capilene Baselayer bottoms offer the comfort of wool with the performance of synthetics in a slim and sophisticated package.

Under Armor UA Base 4.0 Crew

  • Materials: 78% Polyester/22% Elasterell

For the sportier set, Under Armor makes a baselayer crew top that it says is its warmest yet: the soft, brushed grid interior traps air against your skin, creating a microclimate that responds to your shifting temperature.

Under Armor UA Base 4.0 Leggings

  • Materials: 81% Polyester/19% Elastarell

These fully-synthetic baselayer bottoms wick moisture, trap heat and retain heat for low-intensity athletic endeavors.

Alternatives

From yak wool to bamboo, find warmth down the alternative path.

Kora Outdoor Yushu LS Crew

  • Materials: 60% premium Yak wool with 40% superfine Merino

Much like its merino counterpart, yak wool is naturally insulating but still breathable, and this baselayer top from Kora combines them both for a well-insulated, unique feel and fit. At 230gsm, this is a great heavyweight piece for the coldest explorations.

Kora Outdoors Yushu Bottoms

  • Materials: 60% premium Yak wool with 40% superfine Merino

Whether you’re on an expedition or lounging after said expedition, these heavyweight baselayer tights are the perfect compliment to a day spent in the frigid cold of winter.

Bambool Crewneck Top

  • Materials: bamboo rayon, merino wool, and elastane

For the uninitiated, bamboo fabric is surprisingly soft and silky, and this baselayer top from Bambool makes good use of the unique material. Its proprietary fabric is made of a blend of bamboo rayon, merino wool, and elastane — just the right combo of strength, stretch and warmth.

Bambool Legging

  • Materials: bamboo rayon, merino wool, and elastane

These bamboo-blend tights are great for high-intensity, warmer winter days that require just the right amount of insulation: not too much, not too little.

L.L.Bean Silk Underwear, Crewneck

  • Materials: 100% silk fabric

Who doesn’t like a little silk int their wardrobe? Utilize the strong, lightweight powers of the luxury material for all-day warmth and comfort.

L.L.Bean Silk Underwear, Pants

  • Materials: 100% silk fabric

For days when you need just the right amount of warmth without adding a ton of bulk, turn to these silk long underwear baselayers from L.L.Bean. 100-percent silk combines strength and warmth in a minimal package.

One Piece Suits

Channel your inner ninja.

Airblaster Merino Wool Ninja Suit

  • Materials: 55% merino wool, 37% tencel, 8% spandex

All-over warmth, the merino blend way: Airblaster makes one-piece baselayers designed to perform on the slopes. A snug-fitting hood traps warmth, while a front fly offers easy bathroom breaks.

Mons Royale Supermons 3/4 One Piece

  • Materials: 100% merino wool

This 3/4 length baselayer suit is made with Mons Royale’s 100-percent Merino 200, which is warm, breathable and odor resistant.

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