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The Best Base Layers for Runners

Don’t be scared off by the cold. A versatile long-sleeve base layer will get you out the door and keep you warm in the harshest of conditions.

best base layers for runners
Staff, Courtesy of Under Armour

When the temps drop, runners might be inclined to grab that marshmallow puff jacket and then regret the decision several sweaty and too-far-to-turn-back-now minutes later. Staying comfortable while running in cold weather is all about layering. It’s a fine balance—you want to be warm and dry from the outset without overheating or drowning in sweat after the first mile.

Tucking a good base layer under an outer layer is the best way to split the difference. A wool or tech layer snug against your skin wicks sweat away so you don’t come home damp and shaking, and you can wear it on its own if you miscalculated the forecast. Here’s how to become the ace of base of layers (sorry, we had to).

The Art of Layering

The best base layers for running are relatively lightweight and sit close to the skin. That way, you can add more layers as necessary, including a waterproof or windproof jacket. A thin base layer under a light windproof shell might be the magic formula for warmth on a 40-degree day; on a below-freezing day, that same light layer might work just as well under a bulkier jacket. For temperatures below 20, look for a midweight or heavier-weight base layer. If you’re new to running in winter, check our guide to dressing for running in any weather.

The Best Base Layer Fabrics

Start your layering with moisture-wicking fabrics that draw sweat away so you stay dry and cozy. Cotton won’t do it—it absorbs too much water, which is why it takes so long to dry. However, synthetic fabrics, like polyester and nylon, fall into this category; these hydrophobic materials resist water, so they won’t retain moisture against your body.

Natural wool is also one of your best bets. Not only is it odor-resistant and warm, but it also wicks sweat through capillary action, releasing the moisture through small openings in the fabric. If you’ve ever worn a wool sweater, you’ve probably noticed that it doesn’t get wet very easily. You’ve probably also noticed it’s a bit itchy, which is why soft Merino is generally the best option for a layer that sits close to your skin.

How We Tested and Evaluated

There’s nothing I love more than crisp fall morning runs, and yes, even biting cold winter runs. My favorite running attire? A long-sleeve base layer, shorts, and gloves. But in my nearly 20 years of running experience, I’ve run in just about everything. Over the course of those years, I’ve learned what material wicks best, keeps me warm but not too warm, washes well, feels comfy, and stands the test of time. (Ahem, Merino, ahem.)

Every base layer here has been thoroughly evaluated and vetted by me and the Runner’s World test editors. We research the market, survey user reviews, speak with product managers, and use our own experience wearing and running in these base layers to determine the best options. If we haven’t tested a piece of gear ourselves, we’ve chosen ones based on their value, technical fabrics, comfort, looks, and ability to wick sweat and keep you warm and dry when the temp dips. Here are the 13 best base layers for runners.

—Best Overall—

Tracksmith Brighton Base Layer

Brighton Base Layer

  • Lightweight
  • Merino wool blend for performance and odor control

  • Pricey
  • Started pilling after the first few washes

Key Specs

  • Material: 52% wool, 28% nylon, and 20% polyester
  • Special Feature: Seamless construction for a smooth, chafe-free fit

    I will never not include the Brighton Base Layer on a list of the best base layers, because it tops the charts every single time. The Merino wool serves as a wicking base (and naturally wards off odors) making this my go-to base layer on super cold days and single layer on perfect fall days. The construction is seamless, which means no chafing, and the fabric is smooth and comfy so you’ll never (I mean never) want to take it off.

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    —Best Value—

    32 Degrees Heat Performance Mesh Baselayer Tee

    Heat Performance Mesh Baselayer Tee
    32 DEGREES

    • Very inexpensive
    • Lightweight

    • Less durable than more expensive base layers

    Key Specs

    • Materials: Acrylic, polyester, rayon, and spandex
    • Special Feature: Anti-static

      We wear this snug tee on just-below-freezing days with another long-sleeve tech shirt, and the combination keeps us warm for miles. It fits snugly without clinging or feeling uncomfortable, and it does a great job of retaining body heat—especially for the price.

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      —Best Synthetic Base Layer—

      Craft Active Extreme X

      Active Extreme X

      • Versatile
      • Slim fit to remove added bulk

      • Not soft compared to other base layers

      Key Specs

      • Materials: 40% SeaQual polyester, 39% Coolmax polyester, and 21% recycled polyester
      • Special Feature: Waffle-knitted design for comfort and moisture-wicking

        I’ve always associated the Swedish Craft brand with skiing and in-the-mountain extreme sports. Its products are high-quality, durable, and worth the price. But Craft also specializes in running gear, and its base layers go the distance for cold-weather running.

        The Craft Active Extreme X checks all the boxes when it comes to long-lasting warmth: It fits close to the skin, isn’t restrictive, and regulates body temperature while on the move. (Hat tip to the breathable waffle-knit fabric.)

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        —Best Merino Wool Base Layer—

        Smartwool Merino 150 Base Layer Long Sleeve

        Merino 150 Base Layer Long Sleeve
        $68.00 (20% off)

        • Nylon core adds durability
        • Soft

        • Pricey

        Key Specs

        • Material: 87% Merino wool and 13% nylon core
        • Special Feature: Stretch stitching enables movement

          Smartwool is known for its performance Merino wool socks—we’re huge fans. It also takes the cake for its base layer pieces, like this 150. Wait, what’s 150? It means the top has 150 grams per square meter of Merino wool wrapped around a nylon core. (Smartwool also has a thicker 250 model, too; it’s less of a base layer unless you’re marathoning in the Arctic.)

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          —Soft Fabric—

          REI Co-op Merino 185 Long-Sleeve Base Layer

          Merino 185 Long-Sleeve Base Layer
          REI Co-op

          • Soft and itch-free
          • Sweat-wicking

          • Pricey, but on par with other Merino wool shirts

          Key Specs

          • Material: Merino wool
          • Special Feature: Ultrafine material for lightweight warmth

            Yes, REI is one of the go-to outdoor activewear stores for big name brands like rabbit, Nike, Patagonia, and Brooks. But its own REI Co-op line has yet to disappoint. It features affordable, sustainable, and high-quality products, like the Merino 185 Long-Sleeve Base Layer. It’s slightly heavier than the Smartool 150 but not as heavy as the Smartool 250. The soft top is durable, warm, and for those midday, sunny fall runs, it boasts a 30 UPF.

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            —Warm Yet Lightweight—

            Ibex Journey Long Sleeve

            Journey Long Sleeve

            • Comfortable
            • Breathable
            • Lightweight

            • Expensive
            • Looser fit than other base layers

            Key Specs

            • Material: 89% Merino wool and 11% nylon
            • Special Feature: Incredibly lightweight

              Buttery soft, this Merino wool base layer is incredibly lightweight and comfortable, with a barely-there feel. It’s pricey, as most Merino wool is, but it’s a simple, no-frills top that will withstand miles and miles to come. Ibex also makes an incredibly comfortable Merino sports bra (!) and underwear. I’ve got my winter base layers all lined up.

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              —Reflective Design—

              Adidas Own the Run Long Sleeve Tee

              Own the Run Long Sleeve Tee

              • Lightweight
              • Reflective
              • Good value

              • Doesn’t provide enough warmth on its own

              Key Specs

              • Material: Polyester
              • Special Feature: 360-degree reflectivity

                Worn on its own, this lightweight, slightly loose-fitting layer doesn’t provide much winter warmth, despite its long sleeves and thumbholes. But worn under a jacket, it’s the perfect quick-drying intermediary—capable of retaining your core heat while releasing all your sweat and moisture. As the days grow shorter, you’ll also appreciate that the shirt has 360-degree reflectivity for early morning or night running.

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                —Best for Cold Days—

                Under Armour ColdGear Compression Mock

                ColdGear Compression Mock
                Under Armour

                • Stretchy for restriction-free movement
                • Knit fabric lends breathability

                • Not soft compared to other base layers

                Key Specs

                • Materials: 87% polyester and 13% elastane
                • Special Feature: Mock neck for added warmth

                  I bought this Under Armour top more than 15 years ago for high school cross-country. The design has changed a little bit; today’s model is thinner because the company figured out how to provide incredible warmth without added bulk. On brutally cold days, I still bust this top out to serve as a base layer.

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                  —Thermal Heat Retention—

                  Columbia Midweight Stretch Baselayer

                  Midweight Stretch Baselayer

                  • Reflective thermal warmth
                  • Snug fit

                  • Not a running-specific top

                  Key Specs

                  • Materials: 85% polyester and 15% elastane
                  • Special Feature: Retains body heat

                    This versatile shirt has a thermal-reflective silver lining to reflect and retain your body heat, much the way those post-marathon foil blankets do. It finds a balance between feeling warm yet remaining breathable and lightweight, fitted but also loose and comfortable. Wear it solo in the fall and as a base layer in the winter. If you need something warmer for 20-degree days, try the brand’s heavyweight version.

                    And for a cheaper option that still boasts the Columbia integrity and performance, try the Columbia Thistletown Park Long Sleeve Crew. Although not specifically designed for running, its versatility means you can layer it for a workout or keep it in your bag for a comfy, dry post-run wardrobe change.

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                    —Best Women’s Only Base Layer—

                    Athleta Speedlight Top

                    Speedlight Top

                    • Soft and flattering
                    • Cozy thumbholes

                    • No men’s equivalent

                    Key Specs

                    • Material: Nylon and spandex
                    • Special Feature: Hem-grippers for stay-put fit

                      This is the first long-sleeve running shirt in one tester’s post-laundry lineup because of its soft, comfy, and flattering fit. It’s UPF 50+, so it works as a sun-protective outer layer on 40- or 50-degree days or under a vest when the temperature dips below freezing. It almost always feels dry—even when it has no right to, thanks to a lightweight nylon-spandex blend that wicks away copious sweat. And it’s one of the few running shirts our tester owns with long-enough sleeves to cover her wrists, complete with thumbholes that let you hide your hands inside when it’s only slightly too warm for gloves.

                      —Best for Short Torsos—

                      Hoka Merino Blend Long Sleeve

                      Merino Blend Long Sleeve

                      • Great length for people with short torsos
                      • Barely there feeling

                      • Sleeves might be too long on some people

                      Key Specs

                      • Material: 67% wool, 22% Tencel, and 11% nylon
                      • Special Feature: Wide collar for added warmth

                        Shorter folks like me—or anyone with a short torso—know the struggle of finding a proper fitting shirt. Most running tops drop past my hips, but I loved the cut of this extremely lightweight Merino Blend Long Sleeve from Hoka, which hit at my hip bones. The wide collar isn’t quite a mock neck but lent enough protection from gusts. Still, it wasn’t a perfect fit. The sleeves were a touch long, but I was able to fold the cuffs to rest on my wrist. For a breathable, easy-to-layer piece, this won’t disappoint.

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                        —Convenient Watch Hole—

                        Oiselle Flow Long Sleeve

                        Flow Long Sleeve

                        • Lightweight
                        • Thumb and watch holes
                        • Easy to layer

                        • Rough material against skin
                        • Women’s only

                        Key Specs

                        • Material: Nylon and polyester
                        • Special Feature: Thumb and watch holes

                          At first touch, I was skeptical about this top. It’s not buttery soft or cozy like some of my favorite base layers, but never judge a book by its cover, right? I wore this as a single layer for a short, easy run in low 50-degree weather (hi, fall!), and it was a wonderful surprise. No, the Flow isn’t soft, but it’s two-knit texture wicks away sweat and provides warmth. Full disclosure: I heated up in the first half of the run so I took the top off for the back half. It’s so light that I easily carried it a half-mile in my hand. I’m no stranger to a good thumb hole, but the Flow offers a watch hole, which is uncommon enough that I’ve never seen before. The cut of the Flow was great for my 5-foot-2 frame, falling right at my hip bones. Although the top isn’t form-fitting, it’s not too loose, either. I’m looking forward to chillier temps to don the Flow, both as a single layer and a base layer.


                          Mammut Trift Long Sleeve

                          Trift Long Sleeve

                          • Material blend optimizes body temp regulation

                          • Pricey considering it’s only 39 percent Merino wool

                          Key Specs

                          • Material: 59% nylon, 39% Merino wool, and 2% spandex
                          • Special Feature: Versatile across activities

                            This Merino wool blend top is designed for optimal body temp regulation—that’s thanks to a specific arrangement of materials, including Merino wool, nylon, and spandex. The athletic fit sits comfortably on the skin and can easily be layered on blustery cold days. Although not a running-specific brand, Mammut is known for its high-quality products for outdoor activities, including skiing and hiking, making this base layer a must-have for anyone who ventures into the cold.

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