Best Base Layers for Hiking & Backpacking 2026

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After 1000s of nights in a tent across the Triple Crown trails on the PCT, AT, CDT and the Te Araroa, I’ve learned that the layer next to your skin makes or breaks a cold, wet day in the backcountry. When combined with a high-quality hiking mid-layer, fleece jacket, down jacket, and rain jacket to form part of your backpacking layering to protect you from the elements. This is my guide to the best base layers for hiking and backpacking, written for thru-hikers and serious backpackers who care about warmth-to-weight and honest performance, not lifestyle styling.

As a former outdoor retail store manager who now runs BikeHikeSafari independently with no sponsored reviews, I judge these on real trail use. My current top pick overall and best lightweight layer is the Smartwool Merino Classic All-Season, with the Smartwool Merino Classic Thermal as my best midweight option. The core decision is merino versus synthetic: merino wins on odor and warm-when-damp comfort, synthetics win on weight, drying speed, and durability. For how I research and field-test gear, see the Gear Review Policy.

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Quick Picks – Best Backpacking Base Layers

• Best Overall: Smartwool Merino Classic All-Season – my go-to all-rounder. Merino comfort and odor control with a touch of nylon for durability, light enough for three-season backpacking.
• Best Midweight: Smartwool Merino Classic Thermal – more warmth for shoulder seasons and cold camps without going full expedition weight.
• Best Lightweight (Hot/Dry): Patagonia Capilene Cool Crew – fast-wicking for hot, dry desert miles where merino feels clammy.
• Best Premium Merino Base Layer: Icebreaker Merino Oasis Crew – High quality 100% midweight merino that is comfortable and offers several great colors.
• Best Base Layer for Australia & New Zealand: Macpac Prothermals – Polartec Power Grid warmth that’s easy to buy locally in AUS/NZ. My winter base layer for early-morning runs.
• Best Budget Lightweight: REI Co-op Lightweight Crew – solid synthetic performance at a fraction of the premium-brand price.
• Best Budget Midweight: REI Co-op Midweight Crew Top – the cheapest way to add real warmth to your kit.
• More Quality Base Layers: Patagonia Capilene Midweight Crew Top – Heavily discounted and the highest Patagonia quality makes this a good midweight base layer buy right now.

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How We Tested

The base layers in this guide are researched and, where possible, field-tested by an experienced long-distance hiker and former outdoor store manager. Across thru-hikes, shoulder-season trips, and bikepacking trips, I judge base layers on warmth-to-weight, moisture wicking, breathability, odor resistance, packability, durability, and value for serious backpacking. Some of the items were supplied by the manufacturer and some were purchased by the author for this review. For more on how we research and review gear, see the BikeHikeSafari Gear Review Policy.

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Hiking Baselayer Comparison Table

Brand	Weight	Material
Smartwool Merino Classic All-Season Base Layer	150 g/m²	88% merino wool, 12% nylon
Smartwool Merino Classic Thermal Base Layer	250 g/m²	100% merino wool
Patagonia Men’s Capilene Cool Crew	5.4 oz	100% polyester
Icebreaker Merino Oasis Long Sleeve Crew Top	200 g/m²	100% merino wool
Macpac Prothermals	6.7 oz	90% polartec powergrid fleece, 10% elastane
REI Co-op Lightweight Crew	6.4 oz	94% polyester, 6% spandex
REI Co-op Midweight Base Layer Crew Top	9.7 oz	92% polyester, 8% spandex
Patagonia Capilene Midweight Crew Top	6.2 oz	100% polyester

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Best Backpacking Base Layers 2026 – Detailed Reviews

This is the base layer I keep coming back to. The nylon content gives the 150 weight merino enough durability to survive a long trail, and the all-season weight wicks well without overheating on the climbs.

It suits three-season backpacking. It is warm enough for cool mornings, breathable enough for sustained output.

In real use, it manages odor far better than synthetics; I can wear it many days before I start to offend others. The trade-off is that pure-feeling merino blends like this dry slower than full synthetics after a sweaty climb or rain shower.

Trade-off: durability and odor control at a small weight penalty versus pure synthetics.

Best for: thru-hikers wanting one merino layer that does almost everything.

When I want more warmth than the All-Season, this is the step up. Full merino, noticeably warmer next to skin.

Best for shoulder seasons, cold camps, and sleeping warmth.

I love using a merino top like this for sleeping, it doubles as a sleeping bag liner and keeps your ultralight quilt or sleeping bag clean of body oils. Honest trade-off: 100% merino is less durable and slower-drying than blends.

Trade-off: warmth and next-to-skin comfort vs added weight and slower drying.

Best for: cold sleepers and shoulder-season trips.

My pick for hot, dry conditions. I love hiking in this fabric in warm weather such as a hot dry desert, it wicks fast and dries quickly.

Best for desert and summer hiking where heavy merino feels clammy.

If you’re passionate about the environment, Patagonia’s recycled content and repair program are a genuine plus, and it comes in several colors and styles including hoodies and short sleeve.

Trade-off: fast drying and breathability vs merino’s odor control.

Best for: hot-weather hikers and desert sections.

The 200 Oasis is the merino top I keep recommending when someone wants one wool layer that simply works. The 200 gsm jersey sits in that sweet spot between too thin to be warm and too heavy to layer, and the 18.9 micron wool feels soft straight out of the bag rather than scratchy like cheaper wool. It is a best-seller for good reason: it does the basic job of a merino base layer better than most.

This is a three-season workhorse. It earns its keep on cool mornings, cold camps, and as a sleeping layer, and it slides easily under a fleece or down jacket without bunching. It is happiest in dry cold; in tropical humidity, like all merino, it can feel sticky and slow to dry.

What I value most is the odor control. I can wear this for many days on trail before it starts to offend, which means fewer stops to rinse and a lighter pack. It doubles nicely as a sleep top and keeps your quilt or sleeping bag cleaner from body oils and sweat. The honest downside is durability: pure merino this fine wears through faster than a wool-nylon blend, so treat it gently and expect a shorter trail life than a synthetic.

Trade-off: you gain superb odor control and next-to-skin comfort, but pure merino is less durable and slower-drying than a blend or synthetic.

Best for: thru-hikers and backpackers who want a do-everything merino layer and value odor control over outright durability.

Polartec Power Grid is one of my favourite synthetic base fabrics, and Macpac makes it easy to buy in Australia and New Zealand. The fabric allows any sweat to be wicked away from the skin thus keeping you warm and dry, it does this better than merino.

It is my current base layer of choice for thru hiking the Te Araroa Trail in New Zealand or hikes in Tasmania, Australia. I also wear it all winter as my base layer on early morning runs and cool morning hikes. All I need is an outer layer like a windbreaker or rain jacket and I am well protected and quite warm.

Trade-off: warmth and only available in AUS/NZ vs odor control which is not as good as merino.

Best for: AUS/NZ backpackers wanting grid-fleece warmth.

If you’ve found the base layers above a little expensive, the REI Co-op Lightweight Crew may be the better option for you. Solid synthetic performance for the price.

Best for budget-conscious hikers and warm-to-cool conditions.

I like the drop-tail hem for better coverage and the raglan sleeves with underarm panels that give a full range of motion.

Trade-off: low price vs premium-brand refinement vs not so good odor control.

Best for: first base layer on a budget.

The REI Co-Op midweight base layer is very reasonably priced. You may even argue that it’s a bargain.

As a midweight base layer, it’s a little thicker and hence warmer than its lightweight counterparts. But you don’t have to worry about getting sweaty while wearing it because the fabric is designed to wick sweat away. Same comfortable cut as the lightweight base layer listed above; honest trade-off is the usual synthetic odor issue on multi-day trips.

Trade-off: warmth for the money vs merino comfort and odor control.

Best for: budget hikers needing extra warmth.

The Capilene Midweight is the warmer and slightly heavier version of the Capilene Cool. The diamond-grid double knit is the clever bit: the raised grid traps warm air against your skin while the channels between the grid move moisture out fast, so you get a surprising amount of warmth for only 176 grams. It punches well above its weight on the warmth-to-weight front.

This is a versatile cold-weather layer. It works as a stand-alone top on cool spring and autumn days, and as the base of your kit for high-output winter activity where you’ll sweat and need it to dry before you stop moving. Being made from recycled polyester, it is more durable than merino.

In use, the grid fabric is the highlight and works similar to Polartec grid fleece in the way it breathes better than a flat synthetic knit and wicks away sweat quickly, which is exactly what you want on big climbs. The HeiQ Mint treatment keeps odor in check better than untreated polyester, but it will never be as good as merino at odor control.

Trade-off: you get fast drying, strong breathability, and a great warmth-to-weight ratio, but it holds odor more than a merino top on multi-day trips.

Best for: high-output hikers, fast-and-light backpackers, and anyone who prioritises quick drying and breathability over wool’s odor resistance. Note that these have been heavily discounted, so get them quick before they sell out.

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Other Base Layers

The following items are good quality and worth considering.

• Arc’teryx Rho LT Heavyweight Zip-Neck
• Patagonia R1 Air Crew
• Ibex Woolies Pro Tech Crew

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Base Layer Buyers Guide

Size and Fit

You must get the right size base layer for your frame. Base layers that are too tight will be particularly uncomfortable, and base layers that are too baggy will allow the breeze to get to your skin and make you too cold.

As a general rule, the next-to-skin layer should be a snug fit. As they are incredibly stretchy it should not restrict movement too much. Some also have thumb holes or thumb loops to ensure the sleeve will stay down to the cuff when needed.

If you are buying online rather than in-store, I would strongly recommend that you check out the size charts and whether the garments are true to size.

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Fabric Properties

What fabric you use should be your second consideration after size and fit. You need fabrics that will keep you comfortable during your backpacking trip, whatever the weather happens to be doing. I have both Merino and Synthetic as my thermal underwear and each has advantages and disadvantages.

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Merino Wool

Merino is a natural wool fabric that is well known for its anti-bacterial qualities and ability to reduce odor. It also has a natural ability to regulate body temperature. I love hiking in this fabric in warm weather such as a hot dry desert. It can keep me warm when needed and cool me down when needed. But in the tropical humid heat, they are horrible.

I also like using this fabric as a hiking base layer for many days before I start to offend others with my body smell.

But it does have some downsides. It tends to be heavier than synthetics for the same level of warmth and it is not as durable. They can also stick to your skin when you get sweaty and leave wet patches that stay there until they dry. They do not wick as well as most synthetics.

I love to use a Merino Wool Base Layer for sleeping. They make a great alternative to a sleeping bag liner and do a great job of keeping your sleeping bag or ultralight backpacking quilt clean and free of body oils, sweat, and dirt.

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Synthetics

Synthetic Base Layers are improving year on year. One of my favorite materials for a synthetic layer is the Polartec Grid fabric and the newer styles of blends that mix synthetics and wool.

This means that the base layer should help to maintain a comfortable temperature by locking in heat. At the same time, however, they also have to be breathable, and if necessary, offer excellent moisture wicking of sweat and moisture. And if it can also resist body odor, that’s a great plus, too.

Synthetic material does not make good warm-weather base layers. They are best suited to cold weather.

There are other materials such as a silk base layer or bamboo. Silk is great for sleeping in but not much else.

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Odor Resistance

Merino Wool baselayers have an amazing natural resistance to body odor control. The natural anti-bacterial properties lend it well to being used on hiking and backpacking trips which tend to make most people stinky. For that reason, merino wool has no equal odor resistance.

Synthetics tend to hold in bad body smells and don’t do well for odor resistance. But in recent years some fabrics have added polygiene which reduces the growth of smelly bacteria that cause body odor. Having used many items with polygiene I can advise that it works well, but not quite as well as Merino Wool.

Most high-end fabrics used in this review will do a good job of reducing the chances of making your body smell offensive to others.

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Wicking

Wicking is the ability of the fabric to take moisture present on the skin and transfer that moisture to the outside of the fabric so it can evaporate and ensure the body does not cool down in cold weather. It is the moisture-wicking ability of the fabric that makes it best for use close to your skin.

Wicking and breathability work together to allow the sweat to move from the skin to ensure you do not cool down too quickly. But in mild weather, it also serves to allow the moisture to move to the outer fabric to let the wind evaporate and therefore cool you down.

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Breathability

A lightweight layer on your skin serves the purpose of keeping you warm and wicking moisture from sweat away from your skin to allow it to evaporate.

The base layer is the item of clothing next to your skin and it is required to allow the skin to breathe. Therefore, the base layer material should be weaved in such a way to have a moisture-wicking capability that allows moisture to move from the skin to the outer fabric. The more open the weave the better.

In practice, wool layers are not as breathable as most synthetic layers.

When you want to prevent the fabric from becoming too breathable you should use a layering system.

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Base Layers and the Layering System

A lightweight base layer is the first item to be considered when talking about layering. As it is the layer touching the skin it should be comfortable, have good breathability, good temperature regulation, and the ability to wick moisture. They can also be used as a warm weather base layer.

Mid Layers

After the base layer, a hiker needs a good mid-layer for cooler temperatures. Synthetic materials in Mid Layers and Fleece Jackets make good use of fabrics to keep you warm. In very cold weather, warm Down Jackets or Down Vests will be better. All serve the purpose of keeping you warm in cold weather and all come in varying degrees of warmth.

Outer Layers

The outer shell layer should be windproof and protect against the weather. A good waterproof rain jacket is the best option. It will protect against the cold wind and like most backpackers I often use the rain jacket over the top of a base layer to protect against the cold winds.

The quality outer layer will also be very breathable to allow any build-up of sweat, heat, and moisture to transfer through the fabric to the atmosphere. The outer layer also protects against rain and snow.

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Aesthetic

Even when you’re out in the backcountry, it’s nice to be color-coordinated. It’s always a good idea to choose new clothing against how well it goes with what’s already in your wardrobe. Most people, myself included, spend a lot of time in base layers either at home or while in town. So having something that looks a little bit presentable is a good thing.

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Women’s Baselayers

All of the items in the gear review above are available as men’s base layers or Women’s Base Layers. Women’s thermals usually have a slightly different cut than men’s to suit the body shape a little better.

They usually have a much better color selection so your women’s base layer will match up with your favorite color.

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Value for Money 

I would argue that “more affordable” does not always translate to better value for money. Better-quality clothing tends to cost more money than lower-quality items.

But if you do have to be budget-conscious, by all means, check prices as you go along. The REI Co-Op options represent great value for the budget backpacker.

A good set of Base Layers will last a very long time, for most people years. I still have a heavyweight synthetic base layer I bought in Canada in 1996! And I still wear it!

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Care of Base Layers

Base layers are a little more delicate and less durable than a lot of other outdoor clothing. They require a little more thought when washing and drying the clothing.

I once destroyed an expensive set of merino tops and bottoms by washing them with a pair of jeans. The zipper on the jeans managed to rip a series of small holes in all of the thermals. These lightweight base layers need a little extra care when washing.

If possible wash them in a fabric bag or bra bag. This will prevent damage when washing with other items of clothing. Also, consider using a special fabric wash such as wool wash. I don’t bother with this but I know many people do.

A front-loading washing machine will be more gentle than a top-loading machine and try to avoid using a dryer, especially on high heat which may cause the fabric to shrink to an unusable level.

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Conclusion

Overall, here are the best hiking base layers of 2026:

• Best Overall: Smartwool Merino Classic All-Season
• Best Midweight: Smartwool Merino Classic Thermal
• Best Lightweight (Hot/Dry): Patagonia Capilene Cool Crew
• Best Premium Merino Base Layer: Icebreaker Merino Oasis Crew
• Best Base Layer for Australia & New Zealand: Macpac Prothermals
• Best Budget Lightweight: REI Co-op Lightweight Crew
• Best Budget Midweight: REI Co-op Midweight Crew Top
• More Quality Base Layers: Patagonia Capilene Midweight Crew Top

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Frequently Asked Questions

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