The best base layers we tested
Best wool base layer: Minus33 Ossipee Women’s Midweight Wool Crew
Best synthetic base layer: Patagonia Long-Sleeved Capilene Thermal Crew
It’s officially cozy season, so it’s the perfect time to shop for a new pair of the best base layers to wear under your ski clothes or winter hiking outfits. But with so many darn options and a huge variety of price points, it can feel overwhelming to sort through them all yourself. Plus, there’s that looming, age-old question: wool or synthetic?
For one thing, wool apparel has come a long way since the days of scratchy sweaters gifted by grandma. Today, Merino wool makes up a large portion of the base layer market, featuring ultra-fine fibers that wick sweat effectively away from your body and are naturally odor-resistant. Conversely, synthetic fabrics are generally more durable and don’t raise the same animal welfare concerns as wool products. Pro tip: always look for non-mulesed wool or a note from a brand that the wool was gathered safely and sustainably.
I have to admit that when I first started playing hard in the snow, I was a Merino-only person who loved its lightweight warmth on shoulder season backpacking trips and frigid ski slopes. But there’s a wealth of uber-toasty synthetic long johns that dry quicker and often last longer because of their enhanced durability. I spent the last two months testing the top wool and synthetic base layers on backpacking trips in the Rockies, day hikes in Glacier National Park and chilly dog walks outdoors around Boulder. Below are the best wool and synthetic base layers to keep you warm all season.
Best wool base layer
You rarely find a Merino wool base layer under $100, but New Hampshire-born Minus33 has pulled it off beautifully. With a wool weight of 235 grams per square meter (gsm), this crew is warm. Plus, it proved to be durable and decently quick-drying, too. Complete the look with the Midweight Franconia Bottom.
Best synthetic base layer
With its superior sustainability, epic warmth and super-soft feel, our tester loved everything about Patagonia’s Capilene Thermal Crew, even its toasty kangaroo pocket. For more warmth, pair it with the matching Capilene Thermal Weight Bottoms.
Best wool base layer: Minus33 Ossipee Women’s Midweight Wool Crew
Simple design, superior warmth and great pricing are what stood out most when our tester assessed Minus33’s Ossipee Midweight Wool Crew, earning it the top accolade in our wool base layers lineup.
New Hampshire-based Minus33 knows a thing or two about cold weather. It’s been purveyors of affordable Merino wool base layers since 2001, with a huge roster of technical tops and bottoms to meet outdoor lovers’ winter needs. The Midweight Ossipee Crew is one of its top sellers, boasting an impressive 235 gsm of super-soft wool weight and coming in a huge swath of sizes, from XS to 3X. This 235-weight wool was on the higher end of the garments I tested (the highest was REI’s Heavyweight Crew, at 250 gsm), making it solidly insulating for winter sports while still being breathable.
As a midweight layer, the Ossipee Crew is a great fit for most winter enthusiasts’ needs, and the brand recommends it for use in temperatures of 0 to 30 degrees Fahrenheit if you’re working hard and 30 to 60 degrees if you’re more relaxed. In my cardio tests, the garment was excellent at breathability and moisture-wicking, keeping me funk-free on treadmill sprints. Need something with even more insulating material for a winter camping trip, summit bid or ice fishing afternoon? Minus33’s expedition-weight Tanana Crew (400 gsm) should do the trick.
With a UPF rating of 50+, the Ossipee Crew is fantastic to throw on at the top of a frigid peak or on a day hike in chilly winter conditions. Plus, because it has a form-fitting, next-to-skin feel, it’s easy to layer up or down as needed. One thing I would love to see in its next iteration, however, is thumb loops. If thump loops are a must for you, check out the less-warm Ridge Merino Women’s Aspect Midweight Wool Base Layer Long Sleeve Shirt ($75).
Even though its products boast a lower-than-average price point, Minus33 scored well in our sustainability category. It certifies its fabrics to the Responsible Wool Standard, using organic textiles and maintaining both bluesign and Fair Trade certifications in its manufacturing facilities. Its 1-year warranty is shorter than some of its competitors, like REI and Patagonia, but it’s a reasonable enough length of time to discern if there are defects in your product.
I’ve spent dozens of hours walking my dog around Colorado in 45-degree weather, wearing the Ossipee Crew over a simple t-shirt as though it was a lightweight sweater. This fabulous little base layer has kept me warm for over two months now, and I can’t wait to get it onto the ski slopes when the temperatures dip. Match it with the Midweight Franconia Bottom, and you’ll be all set.
Best synthetic base layer: Patagonia Long-Sleeved Capilene Thermal Crew
We’re big fans of Patagonia’s eco-friendly ethos and apparel designs, so it was no surprise when one of the brand’s base layers scored the top spot in our synthetic showdown. With its warm, fleece-like Power Grid fabric, sophisticated color choices and excellent range of motion, we awarded it the best synthetic base layer.
The first thing I noticed when I slipped the Capilene Thermal Crew out of its packaging and onto my torso was its incredibly soft feel against my skin. It reminded me of a toasty fleece jacket with fewer microfiber bits that could shed. Because of the brand’s proprietary Polartec Power Grid fabric, which looks like a waffled grid on the inside of the top, this garment delivered superior warmth compared to every other synthetic layer we tried.
Even though it boasts a fleece-like grid interior, this base layer was still incredibly lightweight and packable, weighing 6 ounces. This made it significantly lighter than the warmest wool layers on our list. This lightweight profile doesn’t mean you’ll sacrifice mobility, though. I could easily complete a 5-minute series of yoga poses in this layer, and I loved tossing it over jeans to wear around my hometown of Boulder.
The top goes on just like a pullover sweatshirt, complete with a cozy pass-through pocket on its front, perfect for warming numb fingers if you forget your gloves. I appreciated this little accent, as every other base layer we tried out lacked a way to warm your hands.
On a particularly blustery day at Mt. Princeton Hot Springs, I took my dog, Marla, for a 5-mile hike near Chalk Creek. Since the forecast was supposed to be a mild 60 degrees, I didn’t even think to bring gloves, and, of course, the unexpected wind meant that I ended up with freezing hands. The kangaroo pocket on the front of the Capilene Thermal Crew saved my precious fingers so I could play fetch with my pup all afternoon, instead of heading straight back to the hotel.
Perhaps best of all, Patagonia’s eco-friendliness is unparalleled in the outdoor industry. Not only is this garment made with recycled polyester and free of harmful PFAS, but it’s also Fair Trade and bluesign-certified. The brand is also excellent about repairing or replacing any item for any reason should it get damaged within its product lifespan. It’s one of the best warranties, ever.
If you’re looking for something just as Earth-friendly but less insulated, check out Patagonia’s Midweight Capilene Crew, which is cheaper at $89. But, if you want to stay extra warm on the slopes or snowy trail this season, we heartily recommend the Thermal Crew, paired with the matching Capilene Thermal Weight Bottoms.
How we tested
Our team did extensive research before making our testing parameters for the best wool and synthetic base layers available online and in stores. They made a selection of the 12 best base layers, then put together a demanding testing rubric of in-the-wild and controlled, at-home tests to see how each one performed.
The base layers that made it into our top handful were put through a series of day hikes in the Rocky Mountains, dog walks around town, overnight backpacking treks, late-season Montana and Utah road trips and controlled, in-home tests to determine which ones were worth your money.
Performance
- Warmth: We took all 12 base layer tops to an elevation of 10,000 feet, where temperatures ranged from 40 to 45 degrees Fahrenheit. Then, we did jumping jacks, stretched our arms, marched in place and stood still for 15 minutes for each top. Top-performing base layers were taken on hikes in Colorado and Montana for additional testing.
- Durability: We noted the types of fabrics used in every base layer we tried, and then every top was washed once in a standard-issue coin-operated washing machine, dried in a commercial dryer, and then examined for signs of wear. The base layers were also each scuffed as hard as possible, ten successive times, against the same rock wall in Boulder. They were then inspected for damage, marks and holes.
- Breathability: We hiked uphill in each of the base layers and assessed how breathable and moisture-wicking each one was and ranked them accordingly.
- Dry time: We submerged every base layer in a bathtub of water, then wrung them out and placed them in the shade to dry in a climate-controlled room set to 74 degrees. We checked every hour to ascertain how quickly they dried, then scored them based on drying time.
Design
- Comfort: We felt the interior and exterior fabrics of each base layer top and noted how it compared to the others on our list.
- Fit: We tried on all 12 base layers on our list and noted how well they fit, relative to standard women’s sizing metrics and relative to their competitors in our rubric. We made extra notes as to whether or not a top was available in more inclusive sizes. We also performed five arm stretches in each layer to assess the mobility they provide in each design while performing athletic tasks.
- Sustainability: We researched each brand’s company-wide sustainability initiatives, and then ranked them against each other. We also noted responsibly sourced wool or recycled materials used in each product we tested.
- Extra features: We also noted the “X-factor” features that some base layers provide, like pockets, thumb loops and a zippered neck. The tops were then ranked by the number of extras provided.
- Price: We considered the standard price for every base layer we tested, and then weighed these prices against each other to determine overall value.
- Warranty: We researched each base layer brand’s warranty information, then scored them according to the overall length, ease of use, repair options and terms.
How to choose the best base layers
The two things you should consider when selecting a new base layer are fabric type and overall warmth. Merino wool and alpaca fabrics make up a massive portion of the base layer market, featuring lightweight fibers that wick sweat effectively away from your body and are naturally odor-resistant. Items containing Nuyarn are even thinner and softer than traditional Merino wool. However, synthetic fabrics are a bit more durable and cheaper, while still wicking away unwanted moisture and insulating when wet. To ensure proper animal welfare, we suggest always looking for non-mulesed wool or a note from a brand that the wool was gathered in a certifiably safe way.
If you plan to travel by plane or go backpacking, check the base layer’s total weight, too, as thicker fabrics, while warm, might not dry as quickly or pack down as small. For wool-based products, there is usually a gsm (grams per square meter) listing that can help tell you how thick and, ultimately, warm the clothing in question is. The higher the number, the thicker and warmer the weave.
Other wool base layers we tested
A warm 250 gsm rating made this one of the warmest layers we tested, though it cost $20 more than our overall wool winner.
We love the silky-soft feel and great durability of REI’s Heavyweight Merino Crew, which comes in a modest three colorways. However, its thicker weight means it might be too warm for many cold-weather cardio enthusiasts, and it costs $20 more than our top prize winner, the Minus33 Ossipee. If you’re a diehard REI member, it’s worth checking out these top and matching bottoms, which are made in a Fair Trade Certified factory.
Smartwool’s Classic Thermal Merino Base Layer is a time-honored favorite, with loads of fun colors and great warmth.
Our tester adored the whopping 26 color options Smartwool offers for its Classic Thermal Merino Base Layer. On trips to Glacier and Conundrum Hot Springs, this layer kept her cozy on subfreezing nights in her sleeping bag. The only downsides were its higher price point and longer drying time, due to the weight of the fabric. Pair with the Classic Thermal Merino Base Layer Bottom for a complete look.
Ridge Merino’s Aspect Midweight Wool Base Layer was cute to wear around town and excellent at quick drying, just not as toasty as some others.
We loved how easy it was to toss on Ridge Merino’s long-sleeved baseball tee-style shirt over jeans for a night out after hiking. Though its fabric was one of the softest we tested in the wool category, our tester found it wasn’t as warm or durable as our overall winner.
Blending function and fashion, Kari Traa’s Rose Baselayer Top boasted excellent warmth at a premium price point.
Read our review
We’re big fans of the vintage Scandinavian floral designs featured on Kari Traa’s legendary Rose base layers. With a gsm of 240, this was one of the warmest wool base layers we tested for this guide. However, its higher price point kept it out of winning our overall category. If you want a warm base layer set, we’d recommend pairing this with the Kari Traa Rose Baselayer Pants.
Featuring body-mapped mesh zones for venting heat in highly active winter sports, Smartwool’s Intraknit Thermal was a bit too spendy to take home our top prize.
With excellent prints and smart thermoregulating technology, we were prepared to fall head over heels for Smartwool’s Intraknit series. However, in practice, our tester found that it performed similarly to the company’s Classic Thermal Crew, which cost significantly less.
As the softest top on our list, Paka’s Everyday Base Layer was easy to pair with trousers and wear around town, it just wasn’t as warm as our top winner.
We love Paka’s ultra-sustainable approach to fashion, which features traceable, sustainably harvested alpaca fabrics from Peru and employs over 200 female artisans. This base layer is unbelievably soft to the touch and lightweight, but it wasn’t the warmest or the most durable on our roster. We’d suggest this top for shoulder season hikes or layering around town.
Other synthetic base layers we tested
With a great price point, excellent product warranty and seasonally rotating color options, REI’s Midweight Base Layer Top is a great budget pick.
Made with bluesign-approved recycled polyester, this form-fitting midweight layer was unbelievably soft to the touch from the moment I first put it on. It could wick sweat while remaining breathable on big cardio days. Its UPF 50+ rating means it will keep your skin protected from the sun, should you bag a peak above the tree line, and its added thumb loops are great for easy layering in truly freezing weather. Though it wasn’t as cozy and warm as our top synthetic prize winner, we highly recommend this top if you’re on a strict budget.
At a stellar price point, this plain Jane, lightweight base layer top was great at wicking moisture when we needed it.
Weighing in at 4.5 ounces, this was the lightest base layer top we tested (the Paka was an impressive 5 ounces). It delivered decent warmth for such a small package but we wish it came in more colors. It also felt constrictive in the chest area, so we recommend sizing up if you’re above a B cup. Our tester also noted that it took all night to dry, even though it was a lightweight fabric.
Patagonia’s Midweight Capilene is a fantastic, eco-friendly choice for high-output activities or warmer winter days in the mountains, as it’s a good deal thinner than our overall synthetic winner.
Our tester loved the great colors and prints Patagonia offers for its lighter Midweight Capilene Crew. This is, essentially, the cooler cousin of our top synthetic winner, sporting a diamond-grid backing to help trap warm air close to the body. It’s also great at wicking away sweat, though not as stink-free as the wool products we tested.
Feeling more like a fleece jacket than a traditional base layer, the Rho Zip Neck delivered impressive warmth.
We tested the brilliant orange Solaris color of Arc’teryx’s Rho Zip Neck and loved it when we needed a high-visibility top for cycling or road running. It wasn’t the cutest or the quickest-drying synthetic layer in our lineup (that prize goes to the Capilene Midweight), but we appreciated its excellent warmth and fleece-like softness on frigid mountain town mornings.
FAQs
Wool is a natural fiber that excels at wicking moisture and repelling gross odors. However, synthetic fabrics are generally more durable and can last longer. Even so, Merino wool is still considered the holy grail of base layer materials, because it is lightweight and insulates even when wet.
Merino wool comes from a specific kind of sheep, and it’s known for being much softer and less scratchy-feeling than ordinary wool fabric. It is naturally antimicrobial, so it doesn’t stink up and it naturally wicks sweat and moisture away from your skin when you exercise.
It’s recommended that a base layer has a slim, next-to-skin fit to effectively trap heat against your body and efficiently insulate you when you’re out in the cold. More space between you and the garment means more ventilation and less warmth.
Why trust CNN Underscored
CNN Underscored editors thoroughly test all the products we cover and provide full transparency about how we test them. We have an experienced team of writers and editors who have many years of testing experience and ensure each article is carefully edited and products are properly vetted. This guide’s writer, Emily Pennington, has been writing and reporting for seven years, has visited every national park and backpacked on five continents. For this story, Pennington got her hands on all 12 base layers and wore them around Colorado, Utah and Montana.
