Best Long Underwear

QUICK LIST OF RECOMMENDATIONS

• Best Long Underwear for Hiking – Smartwool Classic Merino – Men’s Top /Bottom | Women’s Top /Bottom
• Runner Up: Best Long Underwear – Patagonia Capilene – Men’s Top / Bottom | Women’s Top / Bottom
• Top Budget Long Underwear – REI Co-op Lightweight – Men’s Top / Bottom | Women’s Top / Bottom
• Best Midweight Baselayer – REI  Midweight  – Men’s Top / Bottom | Women’s Top / Bottom
• Best Synthetic Long Underwear – Arc’teryx Rho Heavyweight – Men’s Top/Bottoms | Women’s Top/Bottoms

Honorable Mentions

• Outdoor Research Alpine Onset –  Men’s Top / Bottom | Women’s Top / Bottom
• Icebreaker Oasis 200 – Men’s Top / Bottom | Women’s Top / Bottom

Smartwool Classic Thermal Merino Baselayer

Best Long Underwear for Hiking

• SHIRT MSRP: $115.00
• PANTS MSRP: $115.00
• FABRIC: 100% Merino Wool

PROS: Comfortable feel – Excellent moisture-wicking – Great odor resistance – Excellent warmth

CONS: Expensive – Lower durability

LOOKING CLOSER: Merino wool is at the top of our list for best base layers for hiking, and no one has been doing Merino longer than Smartwool. These layers are 100% wool which we love because of the insulating and wicking qualities, as well as odor resistance. Merino is much smoother and softer than standard wool, making these layers feel great on the skin. They are also reasonably lightweight with a solid mid-range warmth rating. Smartwool also maintains high ethical standards for the treatment of the sheep used in their wool production. However, the Smartwool Classic Thermal Baselayer tops and bottoms have a higher price tag than other options and are less durable than synthetic long underwear.

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MEN’S TOPMEN’S BOTTOMS

WOMEN’S TOPWOMEN’S BOTTOMS

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WOMEN’S TOPWOMEN’S BOTTOMS

REI Co-op Lightweight Base Layer

Top Budget Long Underwear Combo

• SHIRT MSRP: $39.95
• PANTS MSRP: $39.95
• FABRIC: 92% polyester/8% spandex

PROS: Lightweight – Comfortable feel – Inexpensive – Excellent wicking – Quick-drying

CONS: Poor odor protection – Low warmth

LOOKING CLOSER: REI’s Lightweight Base Layer tops and bottoms are an excellent choice for the budget-minded hiker. These baselayers excel at wicking moisture away from your skin but come in for less than 50% of the cost of their Merino wool or similar name-brand synthetic counterparts. Made entirely of synthetic materials (polyester and spandex), they are lightweight with excellent quick-drying benefits and offer sun protection with a UPF rating of 50. However, these base layers aren’t as warm as other options and are also susceptible to odor buildup. But if you’re looking for a solid budget option that won’t break the bank, this is undoubtedly the best long underwear for hiking that will still perform very well for multi-day trips.

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MEN’S TOPMEN’S BOTTOMS

WOMEN’S TOPWOMEN’S BOTTOMS

Arc’teryx Rho Heavyweight base layer

Best Synthetic Long Underwear

• 
• TOP MSRP: $150.00
• PANTS MSRP: $120.00
• FABRIC: Polartec Power Stretch Pro 53% polyester/38% nylon/9% elastane

PROS: Very warm – Thigh pocket in bottoms – Versatile use – Very durable

CONS: Very expensive – Slightly less odor control – Few color options

LOOKING CLOSER: If you want a synthetic base layer with the comfort and softness of merino wool, then the Arc’teryx Rho Heavyweight is for you. Arc’teryx has done a phenomenal job developing a material that rivals wool in terms of plush insulation and coziness. In the heavyweight’s case – as you may expect – Arc’teryx generously applied this plush insulation to make one of the warmest base layer sets on the market. From mountain ascents to frigid winter hikes, the Heavyweight does a fantastic job retaining heat and wicking moisture to keep you comfortable. Additionally, the material is blissfully stretchy, so it won’t hold you back when you’re working hard. But the tradeoff for all these benefits is a very hefty price tag and slightly less odor control than pure merino layers. However, if you know you’ll have cold adventures in your future, then the Arc’teryx heavyweight may well be worth the investment for reliable comfort when the temperature drops.

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MEN’S TOPMEN’S BOTTOMS

WOMEN’S TOPWOMEN’S BOTTOMS

Icebreaker Oasis 200

• MSRP: $105.00
• FABRIC: 100% Merino Wool

PROS: Good all-round performance – Reliable

CONS: Expensive – Slightly heavy for the warmth

LOOKING CLOSER: The Oasis 200 base layer presents good performance in almost all categories without any major drawbacks. The warmth, thickness, and durability all sit squarely in the middle of the pack to make the Oasis 200 a solid choice for a wide range of outdoor adventure activities in cool to cold weather. The price, however, is noticeably higher than many other competitors, making this baselayer a significant investment in your backcountry comfort and warmth.

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MEN’S TOPMEN’S BOTTOMS

WOMEN’S TOPWOMEN’S BOTTOMS

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MEN’S BOTTOMS

WOMEN’S BOTTOMS

More Information About Base Layers

Why Your base Layer is Important

Your long underwear, or base layer, will often be next to your skin while hiking or camping, which makes this layer vitally important. The bottom line is that base layers are critical in cold (or potentially cold) conditions to keep your skin warm and dry. If the fabric next to your skin is wet, you will be susceptible to rapid cooling if the ambient temperature drops. If your skin is wet, wind alone can lower your body temperature in an amazingly short amount of time through evaporative cooling. Therefore, the best long underwear for hiking will dry quickly and keep you warm in any weather conditions.

Fabric Options for Long Underwear

Long underwear is available in various fabrics, including wool, silk, cotton, and synthetic blends of polyester, nylon, lycra, and spandex. Each of these fabrics has its benefits and drawbacks, which we expand upon below.

1. Merino Wool (Recommended)

Wool, a natural fiber, is the warmest fabric for long underwear and makes excellent base layers. It is moisture-wicking (i.e., moves moisture away from your skin), insulating, lightweight, and odor-resistant. Its biggest downsides are high cost and lower durability, and many manufacturers combine merino wool with synthetic fibers to negate these drawbacks.

2. Synthetic (Recommended)

There are many combinations of synthetic fabrics used in base layers. The most common materials are polyester, spandex, nylon, and lycra. The more spandex there is, the more stretchy the fabric will be. Conversely, higher lycra content leads to improved insulation. Synthetic long underwear is highly moisture-wicking (moves moisture away from the skin), quick-drying, insulating, and lightweight. It is also the most durable option. The main drawback of synthetic fabrics is poor odor protection, which can be a considerable downside for hiking.

3. Silk (not recommended)

Silk, a natural fiber, was one of the original fibers used by early European mountaineers in combination with wool and cotton layers. Ultimately, today it is not a good choice for strenuous hiking and backpacking compared to other options, but it can still be used for moderate outdoor activities. It is slightly wicking, not very durable, and has medium odor protection.

4. Cotton  (Avoid)

Often the most affordable options for long underwear are made from cotton or cotton-synthetic blends. We strongly advise against having any cotton in your base layer. Cotton absorbs moisture and dries slowly, making it a potentially very dangerous fabric to have next to your skin. The one caveat to our advice to avoid cotton is if you’re hiking in the desert in hotter months, it can be a smart choice. But in those cases, you won’t need long underwear, just a cotton t-shirt.

Why Trust Us?

Choosing the right outdoor gear and apparel can be difficult. But at Wildland Trekking, we live and work with hiking gear every single day. It’s an integral part of what we do, and we understand better than anyone how important it is to have the right equipment. In addition to our vast knowledge of backpacking gear, we also offer:

• Independence – our recommendations are not influenced by partnerships or sponsorships with outdoor gear and apparel manufacturers.
• Experience – as one of America’s top guide companies, we take 8,000-10,000 people on hiking and backpacking tours annually. Since our inception in 2005, we have guided more than 75,000 people into the wilderness.
• Cutting Edge Knowledge – we regularly attend trade shows and pay close attention to the leading edge of new developments.
• Up To Date Recommendations – we update our recommendations regularly as new products are developed and released.
• Dedication to our Readers – we know that the gear we select as our top picks will end up in the field with our readers, and we take that responsibility very seriously. We view our readers as guests on our guided trips, just without the guides. We are committed to helping you be as well-outfitted and prepared as possible for your adventures.

*Disclosure: Some of the links above are affiliate links. At no cost to you, we earn a commission on any products purchased through these links. Any proceeds go to supporting our blog and operations. These affiliate links do not influence the products that we include in our gear round-ups. We only recommend products that we 100% support and that we have used in the field.