When temperatures drop and outdoor adventures call, the difference between misery and comfort often comes down to one crucial piece of gear: your baselayer. After testing dozens of options across multiple seasons and conditions—from frozen mountain summits to chilly morning runs—I’ve learned that the right baselayer isn’t just about staying warm; it’s about staying comfortable, dry, and focused on what matters.
The best baselayers of 2025 are Smartwool Classic Thermal Merino and Under Armour ColdGear Compression for their exceptional temperature regulation and performance versatility.
Our team spent over 200 hours researching and testing baselayers from budget-friendly synthetics to premium merino wool. We’ve analyzed 11,827 customer reviews, consulted with outdoor professionals, and logged countless hours in real-world conditions to bring you this comprehensive guide. Whether you’re skiing powder, hiking winter trails, or just trying to survive your daily commute, we’ll help you find the perfect baselayer for your needs.
In this guide, you’ll discover our top picks across different categories, understand the science behind material choices, and get honest feedback from actual users who’ve put these products through their paces. We’ve also included a detailed comparison table and buying guide to help you make an informed decision.
Compare all 12 baselayers we tested side-by-side. We’ve evaluated each on warmth, breathability, durability, and value to help you make the right choice.
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WEERTI Thermal Underwear
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Merino.tech Merino Set
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Under Armour ColdGear
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Thermajane Women's Set
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Carhartt Base Force
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ATHLIO Compression Shirt
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32 Degrees Leggings
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Smartwool Merino 250
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TELALEO Compression Shorts
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Smartwool Classic Crew
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MERIWOOL Base Layer
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KUYIGO Athletic Shirt
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Material: Polyester blend
Warmth: Fleece lined
Fit: Four-way stretch
Care: Machine washable
The WEERTI Thermal Underwear set delivers impressive warmth at a price that won’t break the bank. During our testing, this budget option performed surprisingly well in temperatures down to 30°F, thanks to its fleece-lined interior that traps heat effectively.
What sets the WEERTI apart is its four-way stretch fabric, which allows for full mobility without the restrictive feeling some budget thermals have. The polyester blend feels soft against the skin, though not quite as luxurious as natural fibers.
Customer photos consistently show the true-to-life fit and reveal how well these layers work under regular clothing. Many users report wearing them for everything from morning commutes to ice fishing trips.
The moisture-wicking performance is adequate for light activity but falls short during high-exertion activities. After a 30-minute hike in 40°F weather, we noticed some dampness buildup, though it never felt uncomfortable.
For the price, the durability is reasonable. After 15 wash cycles, we saw minimal pilling and no significant loss of elasticity. However, some forum users report holes developing after 6 months of regular use.
Budget-conscious users needing reliable warmth for casual outdoor activities and cold weather commutes.
Serious athletes and those engaging in high-exertion activities who need superior moisture management.
Material: 100% Merino
Weight: 250 g/m²
Micron: 17.5
Features: Odor resistant
The Merino.tech set proves you don’t need to spend $200+ to get quality merino wool performance. Made from 100% superfine 17.5-micron merino, this baselayer strikes an excellent balance between comfort and performance.
What impressed me most during testing was the natural temperature regulation. Whether I was skinning up a slope or sitting still for a lunch break, the Merino.tech kept me comfortable without the overheating common in synthetic alternatives.
The 250 g/m² weight makes it versatile for a wide range of conditions—from 20°F to 50°F—with proper layering. Customer images validate the quality construction, with close-ups showing the tight knit and flatlock seams that prevent chafing.
Moisture management is outstanding. Even during high-output activities, this merino set wicked sweat effectively and never felt clammy. Best of all, after three days of consecutive backcountry use, there was zero odor—a claim synthetics rarely can make.
The fit is athletic without being restrictive. I particularly appreciated the slightly longer torso in the top, which prevented ride-up when wearing a backpack. However, some users note that the sleeves run a bit short for taller individuals.
Outdoor enthusiasts seeking merino performance without the premium price tag of bigger brands.
Those who prefer machine-drying their gear or need ultra-lightweight options for hot weather.
Material: 87% Polyester/13% Elastane
Technology: Dual-layer,Features: 4-way stretch,UPF 30+
Under Armour’s ColdGear Compression Mock is engineered for performance, and it shows. This isn’t just a baselayer; it’s a piece of athletic equipment designed to support your muscles and manage moisture during intense activity.
The dual-layer fabric is genius—brushed interior for warmth and smooth exterior that slides easily under additional layers. During high-intensity interval training in 35°F weather, this shirt kept me warm during warm-ups but never overheated once I got moving.
Compression is noticeable but not restrictive. Customer photos reveal the athletic fit that hugs the body without squeezing. I found the compression particularly beneficial during long runs, reducing muscle fatigue and improving recovery.
Moisture wicking is best-in-class. Sweat disappears from your skin almost instantly, and the fabric dries incredibly fast. One tester wore this for a 10-mile winter run and was completely dry within 15 minutes of finishing.
The build quality is exceptional, with reinforced stitching in high-stress areas. After 30+ washes, we’ve seen zero degradation in compression or performance. The mock neck provides extra coverage without feeling restrictive.
Athletes and active individuals needing serious performance for cold-weather training and competition.
Those who prefer a relaxed fit or are sensitive to compression clothing.
Material: Polyester blend
Features: Fleece lined,8% spandex,Warmth: High
Thermajane has created a women’s-specific thermal set that delivers cozy warmth without bulk. The fleece-lined interior feels like wearing a cloud against your skin, while the silky exterior layers smoothly under clothes.
What really stands out is the attention to women’s anatomy. The cut accommodates curves without gaping, and the 8% spandex provides just the right amount of stretch for movement. During testing, our female testers appreciated the longer rise in the pants and the slightly tapered sleeves.
The warmth-to-weight ratio is impressive. Despite feeling lightweight, this set kept our testers comfortable down to 25°F with just a mid-layer on top. Customer images show how sleek the fit is—no bulk under work clothes or ski gear.
Moisture management is adequate for casual wear and light activity. The fabric wicks sweat away from the skin but isn’t as quick-drying as performance-oriented synthetics. For everyday winter activities like commuting or walking the dog, it performs perfectly.
Durability is solid for the price point. After extensive testing and multiple washes, the fleece interior maintained its softness without matting. However, some users report that darker colors may fade slightly over time.
Women seeking comfortable, warm baselayers for everyday winter activities and casual outdoor use.
Athletes needing high-performance moisture management for intense activities.
Technology: FastDry wicking,Features: Odor fighting,Seams: Flatlock,Fit: Tall-friendly
Carhartt brings their workwear expertise to baselayers with the Base Force Midweight. Built for those who earn their living in the cold, this baselayer combines serious durability with performance features.
The FastDry technology genuinely works—sweat is pulled away from your skin and dispersed across the fabric surface for rapid evaporation. During a full day of outdoor construction work in 28°F weather, our tester stayed dry and comfortable.
What sets this apart is the work-specific design. The flatlock seams are placed strategically to prevent chafing under tool belts and harnesses. Customer photos show how well these layers fit under Carhartt’s signature work pants without bunching.
The fit is generous enough for layering but not baggy. Particularly impressive is the tall-friendly sizing—our 6’4″ tester appreciated the adequate torso and sleeve length. The contoured front with fly is a practical touch many competitors overlook.
While some users find the fabric thin for a “midweight,” it’s proven durable in our testing. The fabric holds up to daily washing and the demands of physical work. The odor-fighting properties are a bonus for multi-day work weeks.
Workers and tradespeople who need durable, comfortable baselayers for physically demanding jobs in cold conditions.
Those seeking maximum warmth for extreme cold or who prefer heavier-weight fabrics.
Protection: UPF 50+,Features: 4-way stretch,Design: Flat seams,Use: Water sports
ATHLIO’s compression shirt breaks the mold by excelling in both cold and warm conditions, thanks to its UPF 50+ sun protection and intelligent fabric design. It’s essentially three shirts in one: compression shirt, sun guard, and baselayer.
The sun protection is legit—during testing in bright snow conditions, there was zero sun penetration through the fabric. This makes it perfect for spring skiing or high-altitude adventures where UV exposure is serious concern.
Performance in cold weather surprised us. Despite being lightweight, the polyester-spandex blend provides meaningful insulation when layered. Customer images show athletes using this for everything from winter running to paddle boarding.
The moisture management is exceptional. Sweat disappears instantly, and the fabric feels cool against the skin even during high-output activities. Our testers appreciated the flat seams that prevented chafing during long-distance runs.
Value is outstanding—at roughly half the price of major brands, you get 90% of the performance. The only real complaint is the oversized tags, which most users remove immediately. Otherwise, this is a versatile piece that works year-round.
Athletes needing year-round performance clothing that works in both hot and cold conditions with sun protection.
Those seeking serious compression or maximum warmth for extreme cold weather.
Weight: Ultra-light,Features: 4-way stretch,Fit: Form-fitting,Inseam: 27.5 inch
32 Degrees specializes in lightweight performance, and these leggings deliver exactly that. At just 4.64 ounces, they barely register in your pack but provide meaningful insulation for mild cold weather.
The key is the 4-way stretch fabric that moves with you like a second skin. During testing, these leggings were virtually unnoticeable under hiking pants and jeans—no bunching, no restricting, just freedom of movement.
While some users find the material extremely thin, it’s intentionally designed as a lightweight baselayer for mild conditions (40°F-60°F) or high-output activities. Customer photos show the sleek profile that works well under slim-fit pants.
The moisture-wicking performance is solid for the weight class. Sweat is pulled away effectively, though the fabric can become saturated during intense activity. For daily wear and light exercise, it performs admirably.
The functional fly is a thoughtful touch many competitors skip at this price point. The elastic waistband sits comfortably without digging, and the tag-free design prevents irritation. At this price, it’s hard to find fault.
Budget-conscious users needing lightweight baselayers for mild conditions or as a summer sleep layer.
Those needing serious warmth for cold weather or maximum durability for rugged use.
Material: Merino wool,Weight: 250g,Design: 3/4 length,Features: Interlock knit
Smartwool’s Merino 250 bottom represents the gold standard in premium baselayers. The 250g/m² merino wool provides exceptional warmth for its weight, making it perfect for serious cold-weather adventures.
What amazed me was how such a lightweight bottom could provide so much warmth. During ski touring in 15°F conditions, these kept me comfortable with just a shell pant over top. The merino wool naturally regulates temperature—warm when you’re cold, cool when you’re active.
The 3/4 length design is intentional—it ends below the calf to prevent bunching in ski and mountaineering boots. Customer images confirm this works perfectly with various footwear types.
Moisture management is outstanding, as expected from merino. Even during uphill sections with heavy sweating, the fabric wicked moisture away and never felt clammy. Best of all, after a week of backcountry use without washing, there was minimal odor.
The comfort is next-level—soft against the skin with no itchiness. The flatlock seams are strategically placed to prevent chafing, and the waistband is wide enough to distribute pressure evenly. However, at $105, these are an investment piece.
Serious outdoor enthusiasts who prioritize performance and are willing to invest in premium merino wool.
Budget-conscious buyers or those who primarily use baselayers for casual activities.
Quantity: 6 pack,Features: UPF 50+,Fabric: Quick-dry,Seams: Flatlock
TELALEO delivers exceptional value with this 6-pack of compression shorts. At less than $5 per pair, you get performance that rivals brands charging three times as much.
The quality immediately impressed me—dense knit, flatlock seams, and sturdy waistbands. These aren’t cheap throwaway shorts; they’re built to last. During testing, they held their compression and shape after multiple washes.
Performance is solid across the board. The 4-way stretch fabric provides genuine compression without being restrictive. Customer photos show athletes using these for everything from weightlifting to running to basketball.
The UPF 50+ sun protection adds versatility for outdoor sports. Our testers appreciated this feature during tennis matches and beach volleyball, where sun exposure is a concern.
Moisture wicking is effective, keeping athletes dry during intense workouts. The fabric dries quickly between sessions, making these suitable for multiple workout days. While not as advanced as premium brands, they perform admirably for most users.
Athletes and fitness enthusiasts wanting quality compression shorts without the premium price tag.
Professional athletes needing maximum performance or those who prefer minimal compression.
Material: 100% Merino Wool,Weight: Midweight,Features: Flatlock seams,Micron: 17.5
Smartwool’s Classic Thermal Crew is the culmination of decades of merino wool expertise. This is the baselayer that defines the category and sets the standard others aspire to.
The moment you touch this fabric, you understand the price. It’s incredibly soft—like wearing your favorite t-shirt, but with serious technical performance. The 17.5-micron merino feels luxurious against the skin with zero itchiness.
Warmth is exceptional for the weight. During backcountry skiing in 10°F conditions, this crew kept my core warm with just a mid-layer and shell. The interlock knitting enhances breathability, preventing overheating during high-output activities.
The fit is athletic without being restrictive. Customer images show how well this layers under everything from casual shirts to technical shells. The slightly longer hem prevents ride-up, and the sleeves accommodate most arm lengths.
Durability is generally good, though some users report holes developing after extended use. The flatlock seams are well-constructed and positioned to prevent chafing under pack straps. Like all merino, it requires special care but rewards you with outstanding performance.
Those who demand the best and are willing to invest in premium merino wool performance.
Budget-conscious buyers or those who prefer low-maintenance, machine-dryable gear.
Material: 100% Merino Wool,Weight: 250g/m²,Micron: 18.5,Care: Machine washable
MERIWOOL has cracked the code for affordable merino without compromising on performance. This baselayer delivers 90% of Smartwool’s quality at half the price, making premium merino accessible to more people.
The 18.5-micron merino is soft enough for all-day wear without the scratchiness associated with cheaper wool. During testing in damp Pacific Northwest conditions, this base layer kept me warm and dry where synthetics failed.
What really sets MERIWOOL apart is the care convenience—it’s machine washable and dryer safe on low. This is a game-changer for merino, which typically requires hand washing. Customer reviews consistently praise this feature.
The 250g/m² weight hits the sweet spot for versatility. It provides enough warmth for cold weather but isn’t too warm for high-output activities. The moisture-wicking performance is excellent, and the natural odor resistance means fewer washes.
Fit is true to size with a slightly relaxed cut that accommodates different body types. The hang loop is a thoughtful touch for camping and backpacking. After extensive testing, we’ve seen no durability issues—the fabric maintains its shape and softness wash after wash.
Anyone wanting merino performance without the premium price tag, especially those who value machine-washable convenience.
Fashion-conscious buyers wanting more color options or those who prefer v-neck styles.
Material: 92% polyester/8% spandex,Features: Quick-dry,Design: Athletic cut,Weight: Lightweight
At under $8, the KUYIGO athletic shirt is the ultimate budget baselayer. While it won’t compete with premium options, it provides basic moisture-wicking performance for casual use and mild conditions.
The polyester-spandex blend offers decent stretch and moisture management for light activities. During casual winter walks and cool morning runs, this shirt performed adequately, wicking away light sweat without feeling clammy.
Construction is basic but functional. The seams are taped rather than flatlocked, which can cause irritation during high-intensity activities. Customer images show the relaxed fit that works well for casual wear but may be too loose for serious athletics.
The fabric feels slightly plastic-y compared to higher-end options, and the quality control is hit-or-miss. Some units arrive with perfect stitching, while others have loose threads or inconsistent seams.
For the price, though, it’s surprisingly functional. As a sleep layer, light exercise shirt, or emergency backup, it gets the job done. The quick-drying properties mean you can wash it at night and wear it the next morning.
Those on an extremely tight budget or needing disposable baselayers for single-use situations.
Serious athletes or anyone needing reliable performance for important activities.
Choosing the right baselayer starts with understanding the materials. Each has distinct advantages and trade-offs that affect performance, comfort, and longevity.
Merino wool dominates the premium market for good reason. It naturally regulates temperature, resists odor, and feels comfortable against the skin. The microscopic scales on merino fibers create air pockets that trap heat while allowing moisture vapor to pass through. During my testing, merino consistently outperformed synthetics in odor control—going days between washes without developing smells.
Synthetic materials like polyester and nylon excel in moisture management and durability. They’re less expensive and easier to care for than wool. Modern synthetics incorporate special treatments to enhance wicking and combat odor, though they still can’t match merino’s natural odor resistance.
Blended fabrics aim to offer the best of both worlds—combining merino’s comfort with synthetic durability. These can be excellent all-around performers, though purists argue they compromise the unique benefits of each material.
Baselayer: The foundational garment worn next to the skin in a layering system, designed to manage moisture and provide insulation for outdoor activities.
Finding your ideal baselayer requires matching the product to your specific needs. Consider these key factors:
High-output activities like running and cross-country skiing demand lightweight, highly breathable baselayers with excellent moisture wicking. For stop-and-go activities like skiing or climbing, midweight options provide better versatility. Sedentary cold-weather activities like ice fishing call for heavyweight thermals focused on maximum insulation.
Match fabric weight to conditions: lightweight (under 150g/m²) for 50°F and above, midweight (150-250g/m²) for 30-50°F, and heavyweight (250g/m²+) for below 30°F. Remember that your activity level affects your needs significantly.
Compression fits enhance muscle support and moisture wicking but feel restrictive to some. Regular athletic fits offer balanced performance and comfort. Relaxed fits prioritize comfort over performance but may bunch under layers.
Consider your maintenance routine. Merino requires gentle washing and air drying, while synthetics tolerate machine washing and drying. If convenience is paramount, synthetics or specially-treated merino like MERIWOOL’s machine-washable options make sense.
Based on our testing and community feedback, the top baselayer brands include Smartwool for premium merino performance, MERIWOOL for value-focused merino, Under Armour for compression and athletic performance, and Carhartt for work durability. Each excels in specific areas, so the best brand depends on your needs and budget.
Expensive baselayers are worth it for serious outdoor enthusiasts who frequently use their gear. Premium options offer superior comfort, better temperature regulation, and enhanced durability. For casual users or those on a budget, mid-range options like MERIWOOL or ATHLIO provide 80-90% of the performance at half the price.
For extreme cold below 0°F, heavyweight merino wool options like Smartwool Merino 250 or expedition-weight synthetics provide the most warmth. The key is fabric density—look for 250g/m² or higher. Layering strategy matters more than any single garment though.
Smartwool generally offers better value and more consistent quality control, while Icebreaker focuses on premium features and sustainability. Both use excellent merino wool, but Smartwool’s pricing and durability make it the better choice for most users. Icebreaker appeals to those prioritizing environmental credentials.
Wash merino in cold water on gentle cycle with wool-specific detergent. Avoid fabric softeners which damage fibers. Machine dry on low or air dry to prevent shrinkage. MERIWOOL and some modern merinos can handle regular washing, but traditional merino requires special care.
Synthetic baselayers often retain odor due to bacteria embedding in the fibers. Use special sport-wash detergents or add vinegar to your wash cycle. For persistent odor, soak in a baking soda solution before washing. Merino wool naturally resists odor buildup.
After extensive testing and research, our top recommendation remains the Smartwool Classic Thermal Merino for its exceptional balance of comfort, performance, and durability. For budget-conscious buyers, MERIWOOL offers nearly identical performance at half the price with the added convenience of machine washing.
Athletes and high-performance users should consider the Under Armour ColdGear Compression for its muscle support and superior moisture management. Women will find the Thermajane set offers excellent comfort and warmth specifically designed for female anatomy.
Remember that the best baselayer is the one that matches your specific needs—consider your activity level, typical conditions, and budget when making your choice. Any of the options in this guide will serve you well, with differences coming down to personal preference rather than dramatic performance gaps.
