Apr 7, 2022 9:00 AM

The Best Hiking Shirts and Base Layers for Outdoor Fun

Regulate your body temperature and wick away sweat on your adventures with these blended, merino wool, and synthetic tops.

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Now that we've exited what was seemingly the longest winter ever and entered spring, our thoughts turn to all the warm-weather adventures we're going to have across national and state parks, campsites, climbing walls, and day trails. You might think a snug-fitting top is a garment only for chilly days, but it can be a vital piece of gear for sunny-day treks too.

The base layer (outdoor industry-speak for "undergarment") is the foundation for your entire outdoor clothing system, and it all starts next to the skin. From the choice in fabrics to the location of the seams, a lot of engineering goes into an outdoor base layer that sets it apart from a common cotton undershirt. It has to be comfortable and non-chafing, and it needs to wick away sweat to the outer clothing layers so you won't stay damp. Even on comfortable 70-degree days, you can get hypothermia if you stay wet for too long in a breeze or over the course of a chilly night. There are a lot of undershirts and base layers; few are terrible, but few really stand out. These are our favorites.

Updated April 2022: We've added short-sleeve base layer picks for your warm-weather adventures. We've added the Patagonia Capilene Cool Daily, Smartwool Short Sleeve, and Smartwool Merino Short Sleeve, and we've updated pricing and availability throughout.

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Best Synthetic Short Sleeve
Patagonia Capilene Cool Daily Shirt
While merino wool may get all the accolades for its softness next to the skin, the Patagonia Capilene's 100-percent polyester fabric feels downright luxuriously silky. The Capilene Cool Daily is my day hiking and climbing base layer of choice whenever the sun is out and the mercury is pegged above 65 degrees. It's snug but not at all restricting, no matter how awkwardly I'm craning myself on a rock wall to grab the next handhold. And at such a low price, you can afford to buy several and rotate through them so you always have a fresh one.
$55 at Patagonia (Women's Sizing)
$55 at Patagonia (Men's Sizing)
$55 at Backcountry (Women's Sizing)
$55 at Backcountry (Men's Sizing)
Photograph: Smartwool
Best Wool Short Sleeve
Smartwool Merino Short Sleeve Tee
Wool isn't a cold-weather-only fabric. On a warm hiking day, thin wool base layers can be just as comfortable as a polyester base layer, and this crew-neck shirt from Smartwool is made of very thin merino. It has bit of nylon in it—13 percent, to be exact—but it's in the form of a nylon core that the wool fibers are wrapped around, so what rubs against the skin is all merino. As a welcome touch, the seams are positioned so that they don't run along the tops of the shoulders. That means that pack straps won't have such a tendency to dig into the seams and cause uncomfortable chafing.
$75 at Smartwool (Men's)
$75 at Smartwool (Women's)
$75 at Backcountry (Women's)

Photograph: Smartwool
Best Blended Short Sleeve
Smartwool Short Sleeve Tee
This Short Sleeve's blend of 56 percent merino wool and 44 percent polyester combines the best aspects of merino wool and synthetics. It affords some insulation when the fabric gets wet, which is useful even on hot days if you pass into a shady forest, yet it dries out more quickly than a purely wool garment, thanks to its polyester content. The downsides are that, unlike the merino wool version, the sleeve seams are not set away from where pack straps tend to rest, so you might experience some uncomfortable rubbing during longer hikes.
$50 at Smartwool (Men's)
$50 at Smartwool (Women's)
Photograph: Mountain Hardwear
Best Synthetic Long Sleeve
Mountain Hardwear Ghee Zip-Top
This one's purely synthetic: 85 percent polyester and 15 percent elastane. It's snug-fitting and very soft. Like the Smartwool undershirt above, it's an ideal weight for a base layer. Rather than thumb loops in the sleeves, it has slits in the cuffs for your thumbs to fit. On the one hand, I like that there are no loops to get in my way and annoy me when I'm not using them. On the other, slits make me worry a bit about long-term durability.
The seams don't run across the top of the shoulder, but they do run along the rotator cuff. If your pack straps shift while you hike, they may cause a touch of discomfort on a long trip, but for the most part, this is all the base layer anyone needs. It's more affordable than most of the competition yet doesn't feel or perform worse.
~~$75~~ $52 at Amazon (Men's)
$75 at Bob's Sports Chalet (Women's Hoody)

Photograph: Smartwool
Best Wool Long Sleeve
Smartwool Merino Classic Long Sleeve
I like this base layer from Smartwool a lot. Polyester outdoor wear is getting to be pretty soft these days, but merino wool like this is still supremely comfortable. This shirt is an ideal weight, and the tight weave kept me warm but not too warm. The seams are a tiny bit bulkier than the competition, but not so much that it caused any discomfort—they lie flat and sit off the shoulder, as any half-decent base layer should. The only big drawback? There's no version with a hood.
$90 at REI (Men's)
$90 at REI (Women's)
Photograph: Patagonia
Best Blended Long Sleeve
Patagonia Capilene Air Hoody
After a brief absence, Patagonia's Capilene Air Hoody is back, and it remains a favorite. It's a blend of 51 percent merino wool and 49 percent recycled polyester. All base layers stretch to some extent, but the Air Hoody is particularly stretchy and form-fitting.
Because the material is knit, I expected wind to cut through it, but I was wrong. It's surprisingly good at blocking air for a base layer. It's also nearly impossible to feel the seams. That means no chafing when you're carrying a pack. The Air Hoody is true to its name: very light yet warmer than other lightweight base layers. That can be a positive or a negative, depending on whether your body runs hot or cool.
When the hood is up, you can bring the lower part over your mouth. When it's down, it fits tightly around your neck to trap warmth. I prefer a separate buff, but it's a nice feature. Size up: When I tried one on in my usual size, I looked like Randy Quaid with his belly bursting out of his sweater in Christmas Vacation.
$149 at Patagonia (Women's)
$149 at Patagonia (Men's)

Photograph: Ibex
Best Wool Hoody
Ibex Indie Hoodie
Somebody finally went and put a hood on a good 100 percent merino base layer. Because it has no elastane blended into the fabric, the fit isn't as snug as most of the other base layers in this guide. It is fully featured, though, with thumb loops, a quarter-zip for venting, and lay-flat seams situated away from the contact points of backpack straps and hip belts.
At 185 grams per square meter, the Indie is a bit thicker than the 150-GSM Smartwool 150 merino base layer, but it's still lightweight enough to keep you from sweating too much, as long as you pace yourself. Because it's all merino wool, it actually feels a little less soft than Smartwool and Ibex merino-majority blended base layers. That might sound counterintuitive, but wool feels softer if a bit of nylon is blended in. Still, the Indie Hoodie is a winner. If you're ready to discover the joys of having a hood on your base layer top, but you're also a merino fan, this one's for you.
$170 at Ibex (Men's)
$170 at Ibex (Women's)
Photograph: Icebreaker
Honorable Mentions
Other Base Layers
We've tested more than a dozen base layers. The following are a few others we like, though not enough to give them a slot above:
Tracksmith Harrier Long Sleeve Top for $84 (Women's, Men's): Another blend of merino wool and synthetic, the Harrier is a basic base layer without fancy details or offset stitching. It is senior associate editor Adrienne So's go-to for outdoor runs. The fabric hangs perfectly without clinging or riding up, and it dries within a few hours.
Ibex Woolies Tech Long Sleeve Crewe for $115 (Women's, Men's): This 81-percent merino/19-percent synthetic base layer would be a contender for best merino base layer, except the Smartwool is cheaper. But the fit of the Woolies is great, the flat seams sit away from parts of the shoulders that rub on backpack straps, and the fabric is pillowy soft.
Uniqlo Heattech Crew Neck Long Sleeve T-Shirt for $20 (Women's, Men's): This long-sleeve base layer blend of polyester, acrylic, rayon, and spandex isn't technically an outdoor garment, as the seams are in the wrong places for an outdoor base layer and there are no bonus features, such as thumb-loops. But for a casual day hike or car-camping trip, these sticking points don't matter as much.
Helly Hansen Lifa Merino Seamless Top for $110 (Women's, Men's ($77)): Senior associate editor Adrienne So says it's incredibly stretchy and light, and thin enough to fit under the snuggest mid-layer. It uses a unique two-layer construction where the outer layer is 100 percent merino wool and the interior is synthetic. Ventilated mesh panels on the body and under the arms help with overheating, though it may feel chilly if you're wearing it during low-intensity activities.
Ridge Merino Aspect Midweight for $75 (Women's, Men's): Another blend, the Aspect is made of merino wool spun around a nylon core (84 percent merino, 16 percent nylon). It has offset shoulder seams, flat seams under the arms, and thumb holes that are hidden under a triangular piece of cloth in each sleeve cuff. It's a versatile layer that handled the transition well from walking around in 30-degree-Fahrenheit temperatures to a hot and crowded house party.

Matt Jancer is a staff writer for WIRED who focuses on reviewing outdoor gear. Previously, he spent a decade as a freelance writer covering automobiles, motorcycles, and lifestyle stories for magazines. Some of his longest gigs were at Car and Driver, Outside, Esquire, Playboy, and Popular Mechanics.

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