Best Long Underwear

Best Long Underwear for Hiking and Backpacking

Learn about our top picks for wicking, insulating base layers for hiking and backpacking trips.

On hiking and backpacking trips (particularly in the mountains any time of year or in the desert in the late fall, winter or early spring) long underwear is one of the most important layers to get right. Otherwise known as the “base layer,” long underwear provides multiple important functions including wicking moisture away from the skin, providing the first layer of insulation, and serving as dry camp or sleep wear.

Below you’ll find our top recommendations for the best long underwear for trekking and backpacking adventures. We have included the best wool options, the best synthetic options, the best budget options and more.

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QUICK LIST OF RECOMMENDATIONS

Best all around long underwear comboSmartwool Merino 250 Baselayer Top & Bottom

#2 best all around long underwear comboPatagonia Capilene Midweight Base Layer Top & Bottom

Top budget long underwear comboREI Co-op Lightweight Base Layer Long-Sleeve Crew Top & Bottom

Best lightweight, short sleeve long underwear topSmartwool Merino 150 Base Layer Top (Short Sleeve)

Best 3/4 long underwear bottomsSmartwool Merino 250 3/4 Base Layer Bottoms

KEY CONSIDERATIONS

Wicking Capability

One of the most important attributes of your base layer is that it is wicking, or moves moisture away from your skin. Wicking is a safety function that will help keep you warm and dry while hiking hard in the wilderness.

Quick Drying

Wicking and quick drying are very similar, because the faster a material moves moisture away from the skin, the quicker it dries. However, some wicking materials dry slower or faster than others, so we are treating this as a separate consideration.

Insulation

Long underwear should provide insulation as well as next-to-skin wicking. Long underwear comes in different thicknesses as well as different fabrics, all of which affect its level of insulation.

Weight

As with all items and clothing on a hiking or backpacking trip, weight is an important consideration. The lighter your backpack is, the more comfortable your hiking will be and the less likely you will be to sustain an injury. However, balancing weight and warmth deserves thought and research to find the right clothing.

Durability

Durability of long underwear varies. In general, the more synthetic material a base layer has, the longer it will last. Wool tends to be the least durable of our recommended fabrics. Silk is even less durable. Many long underwear options have combinations of natural fibers and synthetic fibers, which make for wide ranging levels of durability.

Feel

Because the base layer is next to your skin, it should be smooth and comfortable. We have only selected long underwear that has a very nice feel, but still rate each one as there is still some variability. Wool is notoriously scratchy, which is why we recommend Merino wool, which is much softer and smoother than standard wool but with all the same benefits. Silk probably has the best feel, but lacks other properties so finding the balance is key.

Odor Retention

Long underwear is worn against your skin and some times for days without being laundered. Certain fabrics easily house bacteria and others have natural properties that discourage bacterial growth. No one expects to smell good after hiking for days in a row without showering or laundering, but some fabrics will smell bad even after laundering. Others will smell ok out of the washing machine, but within minutes of wearing again the odor returns. Odor retention is an important consideration with your base layers.

Cost

Cost is of course always a consideration for most people. We list the Manufacturer Suggested Retail Price (MSRP) for each recommendation below. This is the price the manufacturer recommends, but it doesn’t mean every retailer will charge that rate. There is also always a chance you’ll find a product on sale.

Smartwool Merino 250 Baselayer

Best All Around Long Underwear Combo

SHIRT MSRP: $100

PANTS MSRP: $100

FABRIC: 100% Merino Wool

COMBO WEIGHT: Mens 20 oz / Womens 15 oz

PROS: comfortable feel, excellent wicking, excellent odor resistance, excellent warmth

CONS: expense, durability

STRAIGHT TALK: Merino wool is at the top of our list for excellent base layer fabrics, 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, giving these items good feel on the skin. They are light in terms of weight, but they are moderate in terms of warmth. Downsides of the Smartwool 250 Baselayer tops and bottoms are their higher price and less durability than synthetic long underwear. (Smartwool maintains high ethical standards for the treatment of the sheep used in their wool production.)

Mens Top

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WoMens Top

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Mens Bottoms

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WoMens Bottoms

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Patagonia Capilene Midweight Base Layer Top & Bottom

#2 Best All Around long underwear Combo

SHIRT MSRP: $59.00

PANTS MSRP: $59.00

FABRIC: Recycled Polyester

WEIGHT: Mens 12 oz / Womens 10 oz

PROS: lightweight, comfortable feel, excellent wicking, quick drying, durability, sun protective, environmentally ethical product

CONS: odor retention

STRAIGHT TALK: Patagonia’s Capilene line of long underwear is one of the USA’s most popular brands, and an excellent choice. In terms of performance, it excels in almost every area. It is effective at wicking, quick drying, insulating with a special design that traps heat, breathable, lightweight and durable.  The price tag is reasonable and significantly less than Merino wool. Our favorite aspect of Capilene base layers though is that they’re made 100% from polyester derived from recycled plastic. The only downside is odor retention, which is common with synthetic base layers. Patagonia treats their fabric with an antimicrobial treatment that inhibits the growth of odor-causing bacteria, but its effectiveness is temporary and odor will inevitably become a negative factor.

Mens Top

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WoMens Top

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Mens Bottoms

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WoMens Bottoms

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REI Co-op Lightweight Base Layer Long-Sleeve Crew Top

Top Budget Long Underwear Combo

SHIRT MSRP: $39.95

PANTS MSRP: $39.95

FABRIC: 92% polyester/8% spandex

WEIGHT: Mens 10 oz / Womens 8 oz

PROS: lightweight, comfortable feel, inexpensive, excellent wicking, quick drying, durability, sun protective

CONS: odor retention, warmth

STRAIGHT TALK: REI’s Lightweight Base Layer tops and bottoms are an excellent budget choice that excel especially at wicking moisture away from your skin. Less than 50% of the cost of their Merino wool or similar name brand synthetic counterparts, they compare very well in terms of performance. Made entirely of synthetic materials (polyester and spandex), they are lightweight with excellent wicking and quick-drying effects. The fabric also offers sun protection with a UPF rating of 50. The main downsides of these garments are their odor retention (which is common with synthetic fabrics) and less amount of insulation due to their lightweight nature and lack of lycra (the most insulating synthetic material.)

Mens Top

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WoMens Top

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Mens Bottoms

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WoMens Bottoms

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Smartwool Merino 150 Base Layer Shirt

Best Lightweight, Short Sleeve Long Underwear Top

SHIRT MSRP: $75.00

FABRIC: 92% polyester/8% spandex

WEIGHT: Mens 6 oz / Womens 5 oz

PROS: lightweight, comfortable feel, odor resistance, excellent wicking, quick drying, versatility

CONS: expense, durability

STRAIGHT TALK: Some hikers and backpackers prefer a short sleeve base layer for versatility, comfort, 3-season use, more conducive front country use (like jogging), lighter weight and other reasons. A short sleeve long underwear top like Smartwool’s Merino 150 Base Layer Top still provides all of the wicking and quick drying properties of a long sleeve top, but can be more comfortable to hike in during the day if it’s going to be warm. Merino wool is comfortable against the skin, and the 150 weight makes it firmly on the lighter side of options. As we mentioned above with the Smartwool 250 Base Layer, one of the biggest benefits of Merino wool is its resistant to odor-causing bacteria. This shirt is almost mysterious in its ability to not smell, which is a wonderful attribute on longer trips (especially if you’re sharing a tent with someone else.)

Mens Top

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WoMens Top

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Smartwool Merino 250 3/4 Baselayer Bottoms

Best 3/4 Long Underwear Bottoms

PANTS MSRP: $95

FABRIC: 100% Merino Wool

COMBO WEIGHT: Mens 8 oz / Womens 6 oz

PROS: lightweight, comfortable feel, odor resistance, excellent wicking, quick drying, versatility

CONS: expense, durability

STRAIGHT TALK: There are some nice benefits to 3/4 length long underwear bottoms. They are lighter weight, cooler if hiking in warm temperatures during the day, better suited for use with ski boots, more conducive to front country use (like jogging), and overall more comfortable for some people. Smartwool’s Merino 250 3/4 Base Layer Bottoms enjoy all the benefits of Merino wool (comfortable feel, great wicking, fast drying and resistance to odor-causing bacteria.) The major downside with these long underwear bottoms is the price, which is expected with most Merino wool products.

Mens Bottoms

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WoMens Bottoms

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More Information About Base Layers

Why Your base Layer is Important

Your long underwear or base layer is what will often be next to your skin while hiking, which is precisely what makes this layer so important. The bottom line is that it’s critical in cold (or potentially cold) conditions to keep your skin dry. If the fabric next to your skin is wet, you will be susceptible to rapid cooling in the case of gradual or sudden drops in temperatures. If your skin is wet, wind alone can drop your body temperature in an amazingly short amount of time through evaporative cooling.

Fabric Options for Long Underwear

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

1. Wool (Recommended)

Wool, a natural fiber, is the warmest fabric for long underwear, and makes excellent base layers. It is wicking (i.e. moves moisture away from your skin), insulating, lightweight and odor-resistant. Its biggest downsides are feel (can be scratchy against the skin) and limited durability.

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; and the more lycra there is, the more insulating it will be. Synthetic long underwear is wicking (moves moisture away from the skin), quick drying, insulating and lightweight. It is also the most durable option. The main drawback with synthetic fabrics is its odor retention, which is a considerable downside.

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 can be used for moderate outdoor activities. It is slightly wicking, not very durable, and has some odor retention but not as much as synthetic fibers.

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, which makes it a potentially very dangerous fabric to have next to your skin. The one caveat to our advice to avoid cotton is that 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.

Cotton scenario: imagine you’re on a mountain backpacking trip, and you’ve been hiking all day with cotton long underwear (i.e. shirt and pants) next to your skin. Your perspiration has been absorbed by the cotton fibers, which are now wet. As you get to camp the temperatures plummet, the wind kicks up and it starts raining. You’re no longer exercising, so your body is generating less heat. You’re hesitant to set up your backpacking tent or change clothes because of the rain, and while you wait it out, the evaporative cooling against your skin begins dropping your body temperature. You have a fleece layer and rain gear over the cotton layers, but the moisture is next to your skin and the wind and cold feel like they are cutting through everything else directly to that layer. You begin shivering and start to lose dexterity in your hands, which makes it difficult to perform basic tasks. It begins to get dark. You start to set up your tent despite the rain, but your lack of dexterity makes it time-consuming, and your tent gets soaked. You begin shaking uncontrollably and start to panic… What happens from here depends on multiple choices, but the point is this situation is entirely avoidable. Rapid cooling can happen quickly and can be difficult to recover from. Bottom line – avoid cotton base layers in the mountains.

 

Why Trust Us?

Choosing the right outdoor gear and apparel can be difficult. At Wildland Trekking, we live and work with gear on a day to day basis. It’s an integral part of what we do, and we understand better than anyone how important it is to have the right equipment. Some of the reasons to trust us include:

  • 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 are always paying 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. 

MORE GEAR RECOMMENDATIONS

Check out our Wildland Gear Guide for more recommendations about hiking, trekking, camping and outdoor gear. We are always adding new products to help our guests and readers make the best choices to outfit their adventures.