The 7 Best Base Layers for Men

Best Overall Base Layer

Smartwool Classic Thermal Merino 1/4 Zip

Smartwool comes out with another winner, especially in colder temps, with the Smartwool Classic Thermal Merino 1/4 Zip. We found this layer warm, breathable, and versatile — not to mention extremely handsome to wear. “Classic” may be in the name, but this base layer comes with a few new features built upon the rock-solid legacy of its brethren. A front quarter zip helps dump any excess heat you may have built up trouncing around a winter wonderland. The top shoulder panel moves the seamlines so they don't chafe when wearing a backpack. “The high collar is one of my favorite features on this top,” our lead reviewer notes. Wool is an almost perfect natural fiber to use for base layers, and the 100% Merino wool utilized in the Classic Thermal Merino is some of the highest quality we've tested.

Fabric Weight Class	Midweight
Measured Weight (Size Large)	11.3 oz
Material	100% Merino wool
Fit	Semi-fitted
Measured Shirt Length (Size Large)	28.0 in

This top excels in colder temps. “This is THE base layer I grab when conditions get really cold,” Simoni says, “but it will feel like overkill when worn in the heat.” When it's beginning to warm up outside, store this base layer in the closet until the first new flakes start to fall again, and pick out a more appropriate layer, like the Smarwool's Classic All-Season Merino, which is great when temps are a bit higher. Despite all the amazing characteristics of Merino wool, one of its weaknesses is durability: wearing it around town for an aprés ski drink will be fine, but pit it against anything abrasive, and you'll earn yourself a night watching movies while sewing on patches. Be mindful when washing and drying too, as improper care can cause undue wear to the Classic Thermal, shortening its lifespan. A synthetic top may be a better choice if you're super tough on gear. The Arc'teryx Rho LT Crew is as heavy and warm as a synthetic base layer could get in our lineup.

Read more: Smartwool Classic Thermal Merino 1/4 Zip review

Best Value for Merino

Merino.tech Crew

We love to sing the praises of Merino wool, but the price can be a real-world barrier to owning a quality Merino piece. For those who want to dip their toes into wool, we wholeheartedly recommend the Merino.tech Crew, a lightweight, 100% Merino wool top knitted with ultra-fine fibers, which give it a soft, itch-free feel. The tight fit makes it excellent for layering below your mid and outer layers during cold outings or for wearing alone while snuggled into a sleeping bag while camping in brisk conditions. “The lighter fabric weight of the Merino.tech Crew is usually what I prefer on my chillier runs. I tend to build up a lot of heat, so a lighter base layer like this works the best for me,” notes our lead reviewer.

Fabric Weight Class	Lightweight
Measured Weight (Size Large)	6.8 oz
Material	100% Merino wool
Fit	Semi-fitted
Measured Shirt Length (Size Large)	29.0 in

The price is great, but there are some trade-offs: the *Merino.tech Crew's 100% Merino wool will be less durable than many other Merino blend tops, like the Smartwool Intraknit Thermal Merino. The addition of polyester to wool helps bump up the abrasion resistance. You'll have to be careful with washing and drying as well. Overlock seams are used instead of flatlock throughout, which may annoy people with more sensitive skin. Fit-wise, “It's a little tight underneath the arms for me,” admits our lead reviewer. If that's all a deal breaker, the truer to size Meriwool Merino 250 Long Sleeve is constructed with flatlock seams. It's also much thicker, warmer, and a bit more durable.

Read more: Merino.tech Crew review

Best Synthetic Bang for Your Buck

REI Co-op Midweight Half-Zip

Those looking for the best value for their hard-earned cash should take a serious look at the REI Co-op Midweight Half-Zip, which performs solidly across the board in our tests. Its thicker, 220 g/sm fabric retained a good amount of heat while we huffed and puffed up the trail, yet it is also quite breathable, meaning your perspiration gets a chance to leave your skin. The fabric is both soft and durable - a trick many of the wool-based layers have a hard time pulling off. For a more price-conscious base layer, it still packs a ton of well-thought-out features, from its stealth thumb loops and half-zipper to its high, padded collar. Flatlock seams throughout round out this well-designed base layer. “Its warmth, coupled with the impressive durability we saw after repeated use, is a winning combination in harsh conditions,” notes our lead reviewer.

Fabric Weight Class	Midweight
Measured Weight (Size Large)	10.0 oz
Material	92% recycled polyester, 8% spandex
Fit	Semi-fitted
Measured Shirt Length (Size Large)	29.0 in

Being a jack of all trades, you're not going to find the REI Co-op Midweight Half-Zip a master of any one standout role. We've tested much warmer base layers and more feature-rich options. If you'd rather have the benefits of wool, the Icebreaker Merino 200 Oasis Half Zip is another partial zip option that scores on par with the REI model. It is just as comfortable and slightly warmer but also slightly less durable. The Arc'teryx Rho LT Crew may be an even warmer synthetic base layer, but it lacks the half zip and thumb loops. For the price, the REI Co-op Midweight Half-Zip pulls off the very difficult trick of working really well in a wide variety of conditions, adding even more value to this top.

Read more: REI Co-op Midweight Half-Zip review

A Comfy, Inexpensive Option for Non-Technical Use

Carhartt Base Force Midweight Crew

For a no-nonsense, simple, comfortable, and fairly durable base layer, grab the Carhartt Base Force Midweight Crew. This is a great top for everyday use, perfect to bring along just in case the weather turns during lunch or a brisk, after-work walk. “I toss the Carhartt Base Force in my pack just in case it gets a little chilly on my bike ride home,” mentions Simoni, our lead reviewer. The polyester waffle knit isn't the warmest, but it's very soft and comfortable, and the loose cut combined with that retro pattern makes for an easy addition to your daily wardrobe. It's built tough enough to be worn as your top layer and isn't so technical that it'll look out of place in casual settings. Plus, you can wash and dry the top with the rest of your everyday clothes. “Because it's so easy to clean — especially compared to my wools — I wear the Base Force Midweight Crew more often,” says Simoni. This base layer is a good value for the performance it lends out.

Fabric Weight Class	Midweight
Measured Weight (Size Large)	9.3 oz
Material	100% polyester
Fit	Loose
Measured Shirt Length (Size Large)	28.5 in

If absolute performance is what you're seeking, the Carhartt Base Force Midweight won't tick all the boxes you're hoping for. Breathability is fantastic, but you pay for it in less warmth. The 100% Merino wool Smartwool Classic All-Season Merino 1/4 Zip will provide better warmth without sacrificing too much breathability. To stay with synthetics that don't look out of place as your top layer, the REI Co-op Midweight Half-Zip will be warmer and would be a good pick if you're going out for more extreme wintry missions in the backcountry.

Read more: Carhartt Base Force Midweight Crew review

Most Versatile Base Layer

Black Diamond Solution 150 Merino Half Zip Hoody

Of all the base layers we have at our disposal, the Black Diamond Solution 150 Merino Half Zip Hoody is the one we've been reaching for no matter the day's objective. “Hands down, the BD Solution 150 is one of my personal favorite base layers. I love all of its little features: the hood, the zip, the thumb loops,” reports Justin Simoni, our lead reviewer. The Solution is a solid 150 g/sm Merino wool blend that hits a sweet spot between a light and mid-weight layer. It has a helmet-compatible hood, half-zip, and extra long sleeves with thumb loops — all of which help you cover up or expose some skin depending on the conditions. The slim, athletic fit works well as a first layer in colder conditions, but it also works well by itself when the temps start to rise or the after-climbing beers start to go around.

Fabric Weight Class	Lightweight
Measured Weight (Size Large)	8.0 oz
Material	Nuyarn: 78% Merino wool, 22% polyester
Fit	Slim fit
Measured Shirt Length (Size Large)	29.0 in

The Solution 150 won't be a perfect fit for everyone: the slimmer cut can be too tight for some body types to wear comfortably — especially if you're worried about the sleeves being too tight around the shoulders and pits. The NuYarn wool blend is a thin, stretchy fabric, but durability is a concern if worn alone and not safely underneath a top layer. If you'd rather invest in a more durable layer, the Ridge Merino Aspect Midweight is a similarly weighted, blended, hooded model to compare this against. It's also important to mention the price of the Solution 150: this is one of the most expensive base layers we've tested. A far more budget-friendly pick is the Merino.tech Crew, although it lacks many of the great features of the Solution. If you can swing the cost of the Solution 150, you may never find yourself not wearing it from when the first flakes fall to when the last ski run closes.

Read more: Black Diamond Solution 150 Merino Half Zip Hoody review

Best Midweight Layer

Smartwool Intraknit Thermal Merino

The Smartwool Intraknit Thermal Merino wins top honors for its weight class thanks to its innovative seamless knitting technology that blends swaths of warm fabric with panels that add durability and ventilation — all without requiring additional seams, which saves on weight and bulk. We think this is a pretty cool innovation, and it seems to work. The slim, athletic fit excels as a base layer, allowing you to top it off with additional layers for a complete system to prepare you for the harshest of conditions. Extra long sleeves, torso, and a drop tail hem ensure that the Intraknit Thermal covers you no matter how you move. The midweight Merino wool blend fabric is a great “just right” weight to use for most cool to cold days outdoors. “The most surprising aspect of the Intraknit Thermal is just how lofty it feels in hand. It's almost like two layers sandwiched together,” notes our lead tester.

Fabric Weight Class	Midweight
Measured Weight (Size Large)	8.0 oz
Material	53% Merino wool, 45% polyester, 2% elastane
Fit	Slim fit
Measured Shirt Length (Size Large)	29.0 in

The Intraknit Thermal isn't without its weaknesses. We've noticed more pilling of the Merino wool blend than we'd like to see on a base layer of this price. The higher price point alone may be enough to dissuade you from purchasing this one. Also, stouter builds may find its slim fit may be too tight for comfort, especially around the shoulders, where pinch points can develop when worn under additional layers. Smartwool's Classic Thermal Merino 1/4 Zip has a more relaxed fit. We're a little surprised that the Intraknit tech doesn't extend to the shoulders, where there are some not-so-awesome seams instead. These can rub and cause chafing where pack straps come in contact. If this is a big issue for you, the REI Co-op Merino 185 Long-Sleeve Half-Zip features a shoulder panel design that completely moves the seam out of the way. Despite these flaws, there's no question about how warm, comfortable, and lofty the Intraknit Thermal Merino is out in the elements.

Read more: Smartwool Intraknit Thermal Merino review

Excellent Value for Cold Winter Days

Meriwool Merino 250 Long Sleeve

You may be surprised to discover that you actually don't have to pay an arm and a leg for a superb Merino wool top. The Meriwool Merino 250 Long Sleeve offers near-top-quality performance at a fraction of the cost of most of the 100% Merino tops we tested. Even though it is firmly in the midweight category, the extra-fine spun wool used to create this layer is more breathable than other directly comparable models, making it a great option for folks engaged in high-output activities like ski touring. Couple that with a slim, stylish fit, and you have a layer you can take from the mountain straight to après-ski. “At the end of the day, I like to keep things simple. I want gear that works without too much fluff. The Meriwool top accomplishes this objective perfectly,” notes one of our lead reviewers.

Fabric Weight Class	Midweight
Measured Weight (Size Large)	8.6 oz
Material	RWS Merino wool
Fit	Slim fit
Measured Shirt Length (Size Large)	30.0 in

Though soft, the Merino wool is slightly itchy initially. “My heart sank a little when I first wore the Meriwool Merino 250 as I felt a little itchy. Once I wore it a bit and after a wash, the fabric began to soften and became far less of an issue,” our reviewer reports. We hope that a future design of this shirt moves the seams off the shoulder top, which can rub when wearing a heavy pack. The more expensive Smartwool Classic Thermal 1/4 Zip has these offset seams. One thing you lose with the low price of the Merino 250 is durability: the extra-fine fibers are no match for anything abrasive, so keep this base layer away from your rock climbing and canyoneering trips. Go with a synthetic base layer, like the Under Armour ColdGear Base 4.0 Crew for something far more durable. Beyond these small critiques, this layer presents a reasonable entry point into all-natural base layers. It is the perfect companion for cool-weather camping during spring and fall, works well for both resort and backcountry skiing, and is certainly stylish enough to be worn casually.

Read more: Meriwool Merino 250 Long Sleeve review

Compare Products

Compare select up to 5 products to compare

	Score	Product	Price
	80	Smartwool Classic Thermal Merino 1/4 Zip Best Overall Base Layer	$120
	77	REI Co-op Midweight Half-Zip Best Synthetic Bang for Your Buck	$60
	77	Black Diamond Solution 150 Merino Half Zip Hoody Most Versatile Base Layer	$145
	77	Smartwool Classic All-Season Merino 1/4 Zip	$95
	75	Smartwool Intraknit Thermal Merino Best Midweight Layer	$130
	75	Patagonia Capilene Midweight Crew	$89
	75	Icebreaker Merino 200 Oasis Half Zip	$115
	74	Under Armour ColdGear Base 4.0 Crew	$100
	74	Arc'teryx Rho LT Crew	$100
	73	Meriwool Merino 250 Long Sleeve Excellent Value for Cold Winter Days	$60
	73	REI Co-op Merino 185 Long-Sleeve Half-Zip	$90
	72	Carhartt Base Force Midweight Crew A Comfy, Inexpensive Option for Non-Technical Use	$35
	72	Patagonia Capilene Cool Lightweight L/S	$59
	71	Ridge Merino Aspect Midweight Merino Balaclava Hood	$90
	71	Outdoor Research Alpine Onset Merino 150 Crew	$99
	70	Helly Hansen Lifa Stripe Crew	$45
	68	Ortovox 185 Rock'N'Wool Long-Sleeve	$110
	67	Merino.tech Crew Best Value for Merino	$50
	67	Outdoor Research Echo Long Sleeve	$52
	64	Access Heavyweight Thermal Crew	$13
	62	Thermajohn Long Sleeve Thermal Compression	$25

How We Tested

For this review, we identified the key metrics essential to effectively grading a base layer top. Then we developed appropriate tests to carry out in the field and lab to test each metric individually. For metrics such as warmth, testing is as straightforward as wearing the garments in cold weather and noting the relative differences. Other metrics, like durability, call for a combination of field use (i.e., chimney climbing and bushwhacking) and lab testing (repeated dry and wash cycles and an abrasion test). From the high desert of the US Southwest to the craggy peaks of the Pacific Northwest, we wore these tops through a variety of activities — mountain biking, climbing, uphill and downhill skiing, trail running, backpacking, and more — testing and assessing their relative strengths and weaknesses along the way.

Our base layers testing is divided among six rating metrics:

• Warmth (25% of total score weighting)

• Breathability (20% weighting)

• Comfort and Fit (20% weighting)

• Durability (15% weighting)

• Drying Speed (10% weighting)

• Layering Ability (10% weighting)

Why Trust GearLab

Our expert for all things comfortable and cozy is Aaron Rice. Growing up on the Atlantic coastline and living up and down the Rocky Mountains for more than a decade, he knows all about making the most out of cold-weather playtime. A passion for winter weather led him to a bachelor's degree in snow and climate science. As a ski patroller and avalanche educator, you can often find him huddled in a snow pit, happily freezing his butt off to discuss the finer details of stellar dendrites. Tester and review author Justin Simoni lives for the rarefied air of his backyard mountains in Colorado and keeps his wits sharp with year-round ascents of Longs Peak — usually with a bike-from-town approach. Simoni has been taking part in long-distance bikepacking races and chasing mountain FKTs for over a decade, including the Tour Divide, Colorado Trail Race, and his own self-powered 14er challenges. If there's one thing he knows, it's being on the right side of chilled on some desolate ridgeline at 13,000', waiting for the warmth of the rising sun and wearing a big grin while he sleeps. Together, these two make a base-layer dream team.

Analysis and Test Results

As a workhorse for thermoregulation, we understand the importance of having the right base layer for your outdoor pursuits. That's why we start with only the best tops on the market and then proceed to field-test the heck out of them. By submitting them to the wear-and-tear of everyday use and a variety of outdoor activities across a spectrum of temperatures and environments, we are best able to dial in which types of layers work best in what situations. We target the most important qualities to analyze and test these layers side-by-side according to these metrics. We offer this comprehensive review to help you land on the best base layer for your own needs.

It is important to note that the scores we assign are determined relative to the other products in the review. We purposefully choose to test the best layers on the market, so a low score in our testing does not mean a product is not worth its mettle. It simply means that it performed poorly in relation to the competition. We understand that your own personal needs will dictate which metrics are most important to you. By testing and rating each of these layers relative to one another, we can highlight which products score highest in the metrics that are significant for how you intend to use your base layer.

What's the Best Value?

The balance between price and value is a fine line to walk when researching a product. The synthetic vs. all-natural fibers argument is a perpetual battle in the recreational apparel world, and we'd like to think of ourselves as conscientious objectors. However, for the sake of producing quality reviews, we must decide from time to time what materials are the best for certain situations. There are certainly pros and cons to each material type.

Synthetic fabrics tend to be less expensive, a touch more durable, and pack down smaller. They also tend to hold onto moisture, retain odors over time, and often don't provide the same warmth-to-weight ratio when compared to their natural-fiber companions. Merino wool tops are typically more expensive and bulkier, but they offer benefits like superior body temperature regulation, moisture-wicking ability, and odor resistance. Merino blends add positive characteristics like durability and stretchiness and can allow thinner fabrics to be made, but they're almost always more expensive than 100% wool. Silk, while incredibly valuable in terms of warmth-to-weight-to-thickness, is a hard sell based on durability alone.

If you're value-minded but want the benefits of Merino, add a little warmth with an all-natural option like the Meriwool Merino 250, a 100% Merino wool layer that is very reasonably priced compared to its direct competition. It is a standout for 3-season recreation and works quite well as an athletic base for the coldest months. For synthetics, we've been very impressed with the values provided by the REI Co-op Midweight Half-Zip. It's fairly heavy, 220 g/sm, which is good enough for wintry excursions, and its price tag will allow you a budget for some aprés ski/snowshoe libations.

The Outdoor Research Echo Long Sleeve is also one of the most value-packed synthetic layers on the market today. This top is versatile as a standalone shirt for activities like running and performs impressively well as a technical base layer. The Helly Hansen Lifa Stripe Crew is one of the more affordable base layers we've tested and is a great layer for high-output activities in cold weather, like cross-country skiing. For a casual layer, the Carhartt Base Force Midweight Crew is affordable even if it's less well-suited to sweaty exercise sessions than a comfy top layer for afternoons cruising around town on your bike or dog walks.

Warmth

As the foundation of your layering system, warmth is one of the most essential qualities to consider in your base layer decision. It is not just about simple heat retention but rather the complex system of thermoregulation. A good base layer should trap heat to keep you warm in cold temperatures while also allowing excess heat to escape when your heart rate climbs and body temperatures rise. It also involves wicking away sweat to keep you dry and protected from evaporative cooling. All of these ingredients are essential to a layer's ability to keep you warm and dry through a range of temperatures. An intensely warm top that doesn't breathe well may work for ice fishing, but it will likely leave you dangerously wet and cold during high-output activities like backcountry skiing.

We wore these layers through the varying temperatures of Fall, Winter, and Spring to test every quality that results in you successfully staying warm and dry. We wore them as we skinned up windblown ridges in the Northwest, rowed through desolate canyons in the Southwest, slept on the frozen dirt after climbing sunny sandstone cracks, and explored trails by bike and foot in Colorado and New Mexico. We also tested them indoors in our pop-up labs to compare them as similarly as we could. The standout tops for well-balanced warmth are the Smartwool tops, the REI Co-op Merino 185 Long-Sleeve Half-Zip, and the Icebreaker Merino 200 Oasis Half Zip. These tops consist of thicker, cushy fabrics that seal in heat while maintaining excellent breathability and moisture-wicking abilities.

For the deep cold of winter, we recommend the SmartWool Classic Thermal. It's the heaviest 100% Merino layer we tested and designed specifically with snow sports in mind.

As an intriguing option to split the difference between light- and mid-weight, the Black Diamond Solution 150 Merino is as equally suited to working hard in the skin track as it is to working all day in the snow. Also, take a look at the Ridge Merino Aspect Midweight Merino Balaclava Hood, which is hooded and has thumb loops, similar to the Solution 150. The Ortovox 185 Rock'N'Wool Long-Sleeve is a bit heavier than the Solution and is very similar in terms of offering a nice middle ground to split the seasons.

Those seeking a layer for highly aerobic activities or versatility across seasons will likely benefit from choosing a lighter-weight, more breathable layer. One of our testers' favorite aerobic layers is the Outdoor Research Echo, which is perfect for 3-season activities like backpacking or trail running. For cross-country and backcountry skiing, we would opt for lightweight layers that still offer a bit of warmth, like the Outdoor Research Alpine Onset Merino 150 Crew or the Helly Hansen Lifa Stripe Crew. If you're a rock climber anticipating long belay stances and short bursts of energy, check out the Icebreaker Merino 200 Oasis Half Zip, which provides a solid level of warmth but still offers impressive breathability.

Some specific features enhance warmth and may help narrow your search for the perfect base layer. Tops like the Icebreaker 200 Oasis, Smartwool Intraknit Thermal Merino, and the REI Lightweight Crew have a drop-tail hem. When skiing, we particularly appreciate the ability to keep our shirts tucked in and snow out of our pants. These design features can also keep your top from rising up and exposing your back and belly when bending over to put on your climbing skins or reaching for that next crimper when climbing. The Ridge Merino Aspect Midweight hoody doesn't feature a drop hem, but both the front and back of this base layer are extra long to make it easy to tuck in.

Breathability

Breathability is the yin to warmth's yang. Alongside warmth, it is arguably the most important quality of an effective base layer. Breathability is tied mainly to the moisture-wicking capability of a fabric. Effectively, this is the ability to collect moisture (sweat) and move that moisture to the outside surface of the fabric, where it can freely evaporate. The breathability of a garment is determined by how quickly and efficiently a fabric can convert sweat to free water vapor. A quality, breathable layer will help regulate your body temperature through a range of environments, regardless of your energy output. A great base layer will effectively work to keep you dry and warm or dry and cool, depending on how it's designed.

Breathability is an extremely important quality during active pursuits and stop/start activities like backcountry skiing, backpacking, or rock climbing. A breathable shirt will allow the moist air hovering over your skin to escape through the material without saturating the fabric, thus keeping you warm and dry. A non-breathable shirt will prevent that moisture from escaping, leading it to condense on the inside of the garment. This leaves you wearing a sweat-saturated shirt that is wet, heavy, and potentially dangerous in cold conditions.

We assess each layer's breathability systematically to back up our findings after months of use hiking, running, skiing, climbing, and biking. We test each layer side-by-side in temperature-controlled indoor environments and use the same short, rigorous exercise routine to work up a sweat. After stopping, we time how long it takes for our skin and the inside of our shirts to dry.

Not surprisingly, the top that earns our highest scores for breathability - the Outdoor Research Echo L/S - is also made from the lightest weight fabrics. It's great for warmer weather and high-exertion activities. As a bonus, it also can be used as a sun shirt since it has a UPF sun protection factor of 15-20, depending on the color.

The Thermajohn Long Sleeve Thermal Compression also scores well for breathability, but we didn't find it as warm as its name suggests. Good breathability was found for the Access Heavyweight Thermal Crew, although its ratio and how warm it is make us feel this top is best for milder conditions. The Carhartt Base Force Midweight Crew also scores well in breathability and is still reasonably warm compared to several other lower-cost synthetic choices. Exceptional breathability scores were returned by the Merino.tech Crew — a 100% merino wool base layer — care of its very lightweight fabric.

Several warmer options made of a Merino blend allow lightweight yet strong fabrics to be spun up into beautifully breathable base layers. These thicker and loftier fabrics are often also airy and easily allow water to move through the fabric. These include the 150 g/m² Outdoor Research Alpine Onset Merino 150 Crew as well as several base layers that also feature front zippers allowing for enhanced thermoregulation like the 150 g/m² Smartwool Classic All-Season Merino 1/4 Zip and the 185 g/m² REI Co-op Merino 185 Long-Sleeve Half-Zip. These all make excellent options when layering up for colder conditions while keeping relatively dry and fresh.

Comfort and Fit

When choosing between options, comfort and fit are usually at the top of the list for many consumers. If a layer excels in all other categories but fits poorly or is uncomfortable, you probably won't wear it. This may be the toughest metric to rate because comfort and fit are ultimately subjective and are dictated by preference and body type. We try our best to give as subjective an opinion as possible when considering all the factors that play into a layer's comfort and fit. We scrutinize each layer and ask the following questions: How does the fabric feel next to skin? Is it soft, itchy, stretchy, static, warm, or cool? Does it glide against your skin or cling too tightly? Is it loose, tight, or constricting in key areas? Are there gusseted underarms, purposeful stitching patterns, or articulated zones to help freedom of movement? You get the idea.

The Black Diamond Solution 150 Hoody reaches the echelons of our ratings for slim, athletic-fit base layers. What sets it apart from the pack is its Merino wool fabric, which we found to be thin yet soft. Long sleeves with thumb holes and a drop tail hem keep longer limbs and torsos covered when reaching for those distant handholds on the warmup route. If you're looking for a similarly weighted athletic fit base layer without the hood or thumb loops, the REI Co-op Merino 185 Half-Zip is a top choice. The gusseted pits give great freedom in the shoulders, which is especially helpful when you layer up and want to avoid pinch points.

For stretchy Merino blends, the Smartwool Classic All-Season Merino 1/4 Zip is the king of the hill. It's the lightest Merino top Smartwool makes and has stitching designed to get out of the way of pressure points while carrying a loaded backpack.

If softness can never be secondary, look no further than the 100% Merino Smartwool Classic Thermal Merino ¼ Zip. The high collar keeps your neck warm, and the quarter zip gets it out of the way when you need some fresh air to circulate. The sleeves are perfectly sized to allow you to roll them up past the elbows and shoulder panels, and the flatlock seams have been moved off the crest of your shoulders. The Ortovox 185 Rock'N'Wool Long-Sleeve also gets five stars for being soft and comfortable next to the skin and is a perfect pick if you're looking to wear something a little lighter.

If you need something synthetic and cozy, try out the Arc'teryx Rho LT Crew, which has a nice soft fleece inner that feels nice against your skin. We also found the Patagonia Capilene Cool Lightweight L/S comfy just because of how svelte it is.

Durability

Durability is a characteristic that we search for in all of our outdoor gear: we often spend more on high-quality products to own less in hopes that what we own will both last us longer and stay out of the landfill. Base layers should adhere to the same purchasing ethics that we apply to all of our consuming habits: buy less, buy quality, and repair when possible. When that's not possible, opt for post-consumer products — many of the polyester layers included in this review are at least made in some part with recycled fibers.

To test durability, we inspect the strength of the fabrics, the quality of the stitching, and the construction of the pieces as a whole. We also drag them up against rocks, roll them in the dirt, bushwhack through manzanita and chaparral to get to beautiful places, and subject them to merciless amounts of washing and drying cycles. To test abrasion resistance in a controlled environment, we grind the fabric a set number of times across a one-foot distance of gritty sandstone to see how it fares (think washboard technique). This specific test gives us a very clear idea of how certain tops will hold up to long-term abrasion.

In general, our test results show that base layers made of thick synthetic fabrics are the most durable. In contrast, 100% Merino wool base layers — no matter the thickness — tend to test as the least durable. Some base layers are made with a Merino wool blend with polyester, nylon, and/or elastane spun with wool fibers. The higher the percentage of other materials blended in, the more durable the fabric becomes. However, the durability never matches that of pure synthetic. Thin fabrics, no matter the fabric type, show lower results in our durability tests.

The Under Armour ColdGear Base 4.0 — a thick synthetic — was our absolute standout, seemingly unaffected by our harsh abrasion test. It would be a good choice for those who are doing heavy work outside. Almost as tough and just as warm is the REI Midweight Half-Zip. It features fabric with a slightly softer hand, and we found it quite comfy for all-day treks and all-day movie-watching sessions. Another durability standout is the Access Heavyweight Thermal Crew. It's an inexpensive option that may be perfect for using on dirty outside jobs.

For how thin it is, the synthetic Patagonia Capilene Midweight Crew also scored well for durability. It would work well as a top layer for warmer days. The Helly Hansen Lifa Stripe Crew held up almost as well and would fit well for a variety of outdoor activities, be it hitting the slopes, going on a snowshoe, or exploring some slot canyons. When choosing Merino, stick with the blends if durability is tantamount.

The Smartwool Classic All-Season also scored as one of the most durable blended tops we tested and should suffice for most activities if worn under a more durable layer and cared for properly when washing.

Natural materials fall behind their 100% synthetic counterparts. Merino wool and silk are notorious for their lack of durability. Both tend to wear holes through quickly and/or shrink and lose their shape after repeated washings. Merino wool has come a long way in terms of durability, and weaving polyester into a Merino to create a natural/synthetic blend increases fabric longevity. For many folks, the performance benefits of Merino wool outweigh the lack of durability, and if you take proper care of your Merino top, it can serve you for a long time. Despite its reputation as a relatively short-lived fabric, several of our testers have gotten many years of use out of theirs. That said, they try to be careful to hang them dry and not wear them every single day (they are certainly comfortable enough to want to do just that in the winter).

Drying Speed

Staying dry is a foundation of being comfortable in the outdoors. Not only can a wet top severely inhibit your ability to find happiness and joy, but it can also be downright dangerous under the wrong conditions. Sometimes, the moisture comes from outside sources, like rain or snow. Other times, it comes from working hard and pushing yourself — aka sweat. No matter where it comes from, a top's ability to dry quickly on the body is important.

The drying speed of a fabric can differ depending on whether it is being worn or left out to dry. But based on our collective experience, we expect a strong correlation between drying speeds and breathability — that is, tops that dry faster on the clothesline also tend to dry faster on our bodies. When dealing with dry times, you may also want to cross-reference them with warmth, as lightning-quick dry times of thinner base layers may also mean a less warm base layer.

Our drying speed test is a simple one. We run all our base layers on a wash cycle, then hang them out, periodically checking when they're completely dry. We give slightly more significance in our scores to thicker base layers that we find have dried at the same time as thinner base layers. To precisely gauge how dry these fabrics have reached during our tests, we weigh the tops to determine how much water is still retained in the garment, rather than relying solely on feel, and then we compare this to the dry weight. Thinner fabrics dry faster than thicker ones.

Our tests revealed that thinner, synthetic shirts like the Patagonia Capilene Cool Lightweight L/S dry super quickly. The synthetic Patagonia Capilene Midweight Crew and Thermajohn Long Sleeve Thermal Compression were not that far behind when it came to drying speed. The polyester Carhartt Base Force Midweight Crew impressed us with its drying speed, adding to its appeal as a casual grab-and-go layer for regular daily outings.

Merino wool claims that it can absorb up to 30% of its weight in moisture before feeling wet to the touch. This seems reasonable, as we have to agitate and compress the wool layers while submerged for the fibers to become saturated — a plus if you are planning to wear these layers alone in wetter, milder climates.

The Merino wool/polyester blend of the Black Diamond Solution 150 Merino Hoody does a great job at resisting moisture absorption. On a backpacking trip, we personally experienced hand-washing this garment in a bubbling creek, hand-wringing it, and hiking in it to have it dry to the touch within an hour.

A surprising finding in our dry test was the Under Armour ColdGear Base 4.0, the thickest synthetic we tested. Despite its thickness, its dry times were more similar to a thinner, midweight layer. Notably, the Merino wool Ortovox 185 Rock'N'Wool Long-Sleeve and Meriwool Merino 250 dry quicker than other 100% wool layers of similar weight.

Layering Ability

The ability to layer well is an often overlooked consideration but is important for practical outdoor use. One of the greatest qualities of a base layer is its versatility, which allows it to be worn as a standalone top or layered in a myriad of ways to keep you warm and comfortable in any temperature or situation.

To test the layering ability, we consider all the ways a top can be layered, and we try all of the combinations with every piece. We note how easily they layer as well as how they fit and feel: next to skin, over a t-shirt, over another base layer, under a sticky and tight fleece mid-layer, a sweatshirt, a puffy, a rain shell, as well as stacked in a full layering system of first (base) layer, mid-layer, puffy, and hard shell. While all of the tops in our review perform well next to skin, a few work great layered in other ways, too.

One of the most impressive in this metric was the Black Diamond Solution 150 Merino Hoody, which comes packed with more features than any other base layer we've tested: thumb loops, long sleeves you can roll up, a hood, and a front zip all provide a plethora of options to regulate temperature. Thanks to the stretchy and soft Merino wool blend and athletic fit, it's easy to toss a layer on top.

We were also impressed layering up with the REI Co-op Midweight Half-Zip, which has a high collar and a front zip to help keep warm and dumb any unneeded heat quickly. The front-facing fabric is smooth and won't catch on any upper layers.

Another standout for its layering ability is the Ridge Merino Aspect. Its balaclava hood adds coverage and stores away easily, staying out of the way of your other layers. The extra-long sleeves are anchored by thumb loops, so this layer won't disappear up your sleeve when you put on an additional mid or outer layer.

For a warmer option, the Smartwool Classic Thermal Merino is both handsome and functional. The quarter zip and cuffs that are loose enough to roll up aid in regulating temperature. Its casual fit means there's room for another thin base layer underneath for added warmth on the coldest days. The Smartwool Intraknit Thermal lacks a front zipper, but the Merino blend lofts up well to be warm yet light all on its own, or it can easily be layered with something else.

For lighter synthetics in warmer weather, the Outdoor Research Echo is ready to be worn on an all-day hike as a sun shirt as well as your base layer under a jacket while you wait for more sunshine and warmth. It's super easy to layer underneath almost anything.

How to Choose a Men's Base Layer

Base Layers play an important role in keeping you comfortable while you enjoy your outdoor passions. Since they're next to your skin, they're what you'll feel when you're hiking a long trail, enjoying a brisk morning bike ride, or traversing over a mountain range on skis.

What's the Difference Between the Types of Fabric?

Natural and synthetics, cotton/wool/polyester — blends! All the different types of fabric can get confusing! When designing a base layer, the goal is to choose fabric that will keep the wearer warm, be breathable, wick away moisture, and hopefully be durable enough to have a long life in your gear closet.

Wool

Wool is one of the most popular choices. Natural wool fibers are spun up into threads and knitted into a soft fabric that naturally traps warm air and prevents it from escaping while also having water-repellant qualities to move moisture away from your skin. And even when wool does get wet, it retains much of its warmth, meaning you won't start shivering once you build up a sweat. Wool can be finely spun to be incredibly soft and comfortable next to your skin. Most of the warmest base layers we highlight are made of wool.

Wool Blends

One of the biggest downsides to wool is its relatively low durability. You'll have to be a little more careful with wool when you're wearing it as a top layer and when laundering. Wool blends counter this fragility, often weaving synthetic fibers with the wool fibers for a more durable material that's resistant to abrasion and getting stretched out, all while minimally impacting the warmth and softness of the wool itself.

Polyester

Excellent base layers can also be found made out of polyester. Depending on how the fabric was manufactured, a polyester base layer can have all sorts of different qualities. When compared to wool, one of the biggest benefits of polyester is better durability, usually at the cost of absolute comfort and warmth for the weight of the fabric. Polyester can also be knitted into a much lighter-weight fabric, and you'll see many base layers that are designed to be worn in warmer summer-like conditions.

Cotton Blends

Cotton blend base layers are the last type of fabric you'll find in our lineup. Cotton is a soft, comfortable, and inexpensive material with which to make a base layer, but it can be problematic and even dangerous in certain situations. When wet, it loses much of its heat retention qualities and breathability. To enhance some of the qualities it lacks, polyester is usually blended into the cotton so that it performs a little better in areas like moisture-wicking and drying speed. You'll find budget pieces and more casual choices in our lineup that use a cotton blend, but overall, this is not the material we would encourage you to select if you need to stay warm in the elements.

What Seasons Are You Shopping For?

Most of the base layers in our review are meant to keep you warmer as the foundation for your layering system. If you're looking for a base layer to be worn outside in the winter, consider a heavier-weight base layer that will retain more heat. Wool layers are usually sold with the weight specified in grams per square meter (g/sm), while synthetics are usually just labeled as lightweight, midweight, and heavyweight.

If you're planning to be actively moving rather than just standing still, look for a base layer that's highly breathable. Sometimes, these two qualities aren't found in the same base layers: warmer tops just don't breathe as well as less warm tops, so the base layer that works great for skiing won't be best for backpacking in August.

How Much Do You Want to Spend?

We're not always blessed with an unlimited budget, so price plays a big role in our choice for any of the gear we rely on to pursue the things we love. By and large, the most expensive base layers are the wool and wool blends, with polyester base layers filling out the midfield. Cotton blends are found ultimately in the lower end of choices when it comes to price.

If budget is extremely tight, look into the cotton blends, but be realistic about the performance they'll give you. They may be best for more casual wear where you won't be putting yourself in a potentially serious situation high up a snowy mountain ridge. The best value for the price could come from the polyester base layers, especially when you factor in how durable the fabrics usually are. For a small weight penalty over wool, they can be almost as warm as the warmest wool. For the absolute best performance, look at wool, but be aware that wool is going to also be one of the most expensive options. However, some manufacturers are starting to produce more affordable wool options.

Conclusion

With such a wide array of options out there, it can be tough to narrow your search down to the layer that best suits your body type, internal temperature inclination, and intended uses. We conduct all of our tests and summarize our experiences to try and help you choose the layer that will become your adventure sidekick for years to come. You need to consider activities, temperature ranges, features, and qualities when choosing a new base layer top. We wish you luck in your honorable pursuit of having fun outside.