10 Best Thermal Underwear & Base Layers Tested & Reviewed
We put a lot of research into what makes a great thermal base layer and laid out some serious thermal underwear options for you. Each piece of the best thermal gear offers all the newest materials and features there are in the most current designs. We made sure to also add this info in our FAQs and Criteria sections.
All this information is there to help you find the best products for your next outdoor excursion. Whether you need some wicking wool or just some simple layers, we are sure what we gathered will accommodate any of your needs.
In a Hurry? The test winner after 22 hrs of research
- Warm, yet light
- Very comfortable
- Looks good on and feels even better on
- Great quality
10 Best Thermal Base Layers
1. Smartwool NTS Mid 250 Zip T
- Warm, yet light
- Very comfortable
- Looks good on and feels even better on
- Great quality
- Dries slowly
Smartwool NTS Zip T is an affordable option to your thermal underwear arsenal that doesn't skimp on the warmth and cozy option either. The natural moisture-wicking merino wool, polyester and spandex combination will keep you dry and warm without the itch.Read more
As we mentioned, SmartWool 250 is made from 84% polyester, 11% Merino wool and 5% Spandex. Each part of the mix offers a different aspect to the soft and warm material.
Polyester breathes and adds durability to the structure of the material while the merino wool’s natural moisture-wicking pulls the sweat away from the skin and keeps you dry without holding in the moisture. The spandex allows the fabric to hug the skin and gives it just enough elasticity to not chafe while moving with the body. It sits well under other garments and doesn't slide around.
That small percentage of merino wool adds a large amount of breathability to the Smartwool NTS Zip T material. Merino wool helps temper the body while you are warming up or cooling down. It uses the vapors to help keep your temperature consistent while using the air to dry so you don’t get any sweat build up from activity.
A great addition to the breathability factor is the front zipper that hits midway through the chest. If you find yourself getting too warm and don’t want the neck up, just un-zip and you have more heat release, making a more arid fit.
Offering this shirt in women and men’s sizes give options to body styles and fit preferences. SmartWool NTS is a long sleeve, athletic fit, T-shirt design that hugs the body, which is due to the added spandex. It does not restrict but sits nicely under other clothing without chafing or discomfort.
As an added layer of skin, you won’t be bothered by friction. The Polyester gives the thickness to the material and keeps it durable as well. This gives a softness to the fit of the shirt that 100% wool sometimes doesn’t offer.
You're going to pay a little more for this one but you are getting you're getting more. It offers so much warmth and comfort and fits like a body glove.
You won’t have to stress about putting it through some activity either. Smartwool NTS Zip T is blended for versatility and durability. Each thread works together to stay together while keeping you warm.
2. Duofold Mid-Weight
- Mid-weight and warm when layering
- Quality fabric
- Size runs true to fit
- Very affordable
- Not as stretchy
- Can be loose around the legs
Duofold Mid-Weight has a two-ply cotton construction blend that will keep the consumer warm, and flatlock seams and a moisture-wicking waistband. It has rib-knit cuffs and consumers won’t have to worry about chaffing with this option. This is among the most popular and highly-ranking base layer bottoms because of its warm, comfort and quality and affordability.Read more
Soft and comfortable, Duofold’s base layers and thermal underwear are 60% cotton and 40% polyester. It has flatlock seams for no chafing and moisture management tech that wicks away moisture to keep the skin dry without losing heat retention.
Since it has two layers of fabric blended together, consumers can rely on these thermal pants keeping them toasty. This is a mid-weight pant, ideal for layering under jeans for outdoor work hiking or camping, under jogging pants for running or other workouts.
This thermal pant has a close-to-body fit that is slim and has a convenient front fly. It comes in a few color options including black and winter white.
3. Paradox Performance Merino
- Blend of materials including spandex and merino wool
- Zipper pullover design
- Thumb holes on sleeves
- FreshGuard keeps odors away
- Soft and comfortable
- Helps regulate temperatures
- Athletic fit
- Sizing runs small but long
- Not much merino wool content
The Paradox Performance base layers and thermal underwear is a super comfortable, fast drying layer that is sure to keep you warm and cozy no matter where your adventures take you. It is an affordable option made with a small amount of merino wool for a soft, moisture-wicking build.Read more
The fabric of this shirt is made up of 84% polyester and 11% merino wool to wick moisture and leave you feeling dry and comfortable. The blend also contains 5% spandex, so it will have a decent stretch while retaining its shape and providing a close fit.
Warmth and Breathability
Although the amount of merino wool is small, it is helpful in keeping you warm while still being breathable without having to be too thin. It will help you stay warm when you are cold and keep you nice and cool when you are warming up.
Style and Fit
The cut of this shirt is athletic so you have a close fit and good mobility without sacrificing warmth or comfort. The sleeves have thumb holes which are great for keeping your base layer in place and providing a little extra coverage over your hands and wrists. The zipper design also allows for a little wiggle room and ventilation.
4. Carhartt Base Force
- Keep you warm in winter
- Good quality and thick
- Affordable price
- Runs longer in length
- Ankle cuffs feel too tight for some
Made from 100% cotton, these moisture-wicking leggings will keep the lower body warm and dry when sweating out in the cold weather. With its snug fit and elastic waistband, these underwear pants won’t be falling down when running. This option is thick and comfortable, an ideal for braving the cold winter temperatures for outdoor workouts or adventures.Read more
The material of this base layer pants is 100 % cotton ring-spun knit reinforced stitching. It includes rib-knit cuffs to keep the warmth in, and a tagless label to ward off neck irritation when layering. It also features stain breaker technology to help to get rid of stains when washing.
Warmth and Breathability
The Carhartt underwear pants weigh 9.5 ounces, making them heavy enough to keep the legs warm. The moisture wicking properties help to keep away sweat so that you stay dry. While being nice and toasty, they are still breathable and promote mobility when using as an underlayer.
Style and Fit
Available in both black and a neutral color, these leggings have tight fit without being like compression leggings feel. They have a simple style is that is universal across all types of consumers.
- Comes as a set of both underwear long sleeve shirt and pants
- Soft and warm
- Not as breathable
- Not as stylish as other options
- Loose around the chest and shoulders
This thermal onesie is fleece lined, soft and comfortable, and even though it will keep the consumer warm, it is also breathable so no worries about overheating when on the slopes. With moisture wicking properties and an elastic waist, this set comes in multiple colors. It’s ideal as an underwear option for outdoor sports in the winter like skiing, hiking and more.Read more
This thermal underwear top and bottom set is made with 95% cotton and 5% elastane. The long sleeve shirt is midweight and features no tags so it won’t be itching the back of the neck when used as base layers and thermal underwear. The leggings are fleece lined and are equipped with an elastic waist to keep them from sliding down.
Warmth and Breathability
The Long Johns are perfect for winter sports or activities, or can even be worn as pajamas when camping or at home for those chilly nights. This underwear isn’t too thin, or too thick—being a great mid-weight option for layering when it's freezing to add extra warmth when outside.
There are claims that are breathable, but this isn’t the best when it comes to ventilation since they are on the thick side. The fabric is moisture wicking but does take a longer time to dry than other options.
Style and Fit
Hides great under clothes with a snug fit, the Ekouaer base layering set isn’t constricting or bulky. The material is ultra-soft for optimal comfort and of good quality. It comes in multiple color options for both men and women.
6. Minus33 Katmai Expedition
Great for Extreme cold
Soft to the skin Cuffs work well
Not good with jeans.
Made with 100% merino wool, Minus33 Katmai Expedition bottoms are made to protect and keep warm in the coldest of climates. They are activewear and designed to work with you while you are hiking, running, or participating in your favorite X-treme sport. As an extra layer of cozy skin, you’ll be tempered and comfortable.Read more
400g of 100% merino wool is what Minus33 is offering in the Katmai Expedition. This ultra sweat-wicking material is machine and drier proof, making it easy to care for as well. It is extra soft and made to work in some of the most extreme temperatures.
Merino wool is known for keeping the body tempered and sweat-free no matter what you are doing. However, the material isn’t light and is made fo getting in extreme activity in extreme environment. This is the reason they are called Expedition, they are Minus33’s expedition weight bottoms.
To add to the soft, sweat-wicking, durable merino wool, these offer 50+ SPF rating. When your out, you get sun and it helps when you don’t have to worry about a burn while your clothed. You never know what elements you’ll find yourself in when you’re having fun.
The KatamaiExpedition is also sewn with flat seems and doesn't have any togs to cause irritation. You’ll also enjoy the convenience of the stretchy ribbed cuffs. These ensure you're not bunching up and can out that top layer on without any interference.
Retaining heat is the name of the game and Minus33 does that while still allowing room for air. This teamed up with the wicking properties create a consistent layer or warmth.
Furthermore, their slight compression design helps blood flow. Good circulation keeps you warmer as well. The colder you are the slower your blood flows, just another reason why good circulation is important. It also helps prevent cramping and other running and high activity ailments.
With a large range of sizes in both men and women's models, you get a large selection to get the most customized fit possible. We also mentioned the ribbed cuffs, which offer a secure fit around ankles.
You’ll also know the fit is right in these when they fit you snug without restriction. Thermal underwear should hug, warm and feel good against the body and the Katmai Expedition does all of this well.
Worth the money is what consumers are saying. We like that kind of feedback and from what we have gathered, those words can’t be truer. Whether you're hunting, skiing or working out in the elements, Minus33 is offering you a soft warmth made of 100%softened merino wool. You won’t want to take them off,
7. Arcteryx RHO AR
- Great for layering
- Durable and comfortable
- High collar and zip neck
- Takes time to dry when really wet
- Not as breathable as other options
With its trim fit and zip neck design, this underwear top features moisture-wicking fabric with plenty of ventilation. It’s comfortable, warm, durable and layers well. It’s available in multiple colors and even has a chest pocket for storage.Read more
Made from 90% polyester and 10% elastane, this base layer features Polartec Power Stretch. This means the material can stretch with movement, yet resilient enough not to lose its shape. This high-performance fabric wicks moisture, and it also features a flatlock construction that improves next-to-skin comfort.
Warmth and Breathability
Because of its Polartec Power Stretch material, this zip neck shirt is supposed to be breathable but is lacking when compared to other Arc'teryx base layers. It does do a decent job when it comes to moisture management, but also not as well as the previous options on this list. While the zip neck adds to its ventilation, its tall collar helps to ward off the weather elements like the wind. The mid-weight fabric is heavy (at 10 oz.) and warm, and its trim fit further aids to its thermal efficiency.
Style and Fit
Its design makes this one of the most stylish options on this list. It has a single laminated chest pocket for holding personal items like money when going for a long run or hike. It has a trim fit that is next-to-the-body without being constricting and is perfect for layering. Its high-performance weather protection makes it versatile across various outdoor activities.
8. TSLA Men's Thermal
- Great insulation
- Fits well
- Can run small for bigger builds
- Fabric stretches after multiple washes
Looking for a good pair of thermal underwear to add to your wardrobe this winter? Runners need t stay warm and dry but adding too many layers can make it hard to run. That is why the TSLA Men's Thermal leggings are a perfect bottom layer to put on!Read more
These thermals are made to be used by runners and other active individuals who need an added layer of protection from the cold but who do not want to be impeded by bulky layers. The TSLA Men's base layers and thermal underwear are great for cold weather protection.
The design of these thermal leggings is such that it easily traps body heat where it belongs while still allowing full range of movement in the legs and torso. It will protect you against the cold chill of winter weather!
These pants are made from 90% Polyester and 10% Polyurethane. Excellent elasticity with an enhanced range of motion is the key to their popularity among runners and athletes of all skill levels. The material is soft and comfortable and hugs you tightly for compression control that makes your runs more enjoyable.
The TSLA Men's Thermals do tend to run a little small so it is advised to buy one size up to ensure a good fit. They are designed to be compression legging so you can expect a snug fit so if this is not what you are looking for then this might not be the ideal choice for you.
The bottom line is the TSLA Men's Thermal base layers and thermal underwear is a good choice for runners looking for a good underlayer to add to their winter running wardrobe.
9. WuhouPro Women's Long-John Set
Protection from cold
Stretch for FIT and flexibility
Ensure you choose the correct size for you
Comfort, warmth, and protection can all be yours with the WuhouPro Women's Long-John Set! Available in any bright and cheerful colors this is a great set to add to your winter run workout gear collection. Check it out today for yourself!Read more
These thermal tops and bottoms are made to be used by runners needing a great layer of soft and warm comfort added to their winter running gear. WuhouPro Women's Long-John Sets are great for cold weather protection while still allowing you the chance to show off your unique style.
These thermals are made to be a little looser and worn as a middle layer for your cold weather runs. They are resistant against the cold and wind but are not waterproof and will absorb water if they get wet.
These base layers and thermal underwear are made of 92% Microfiber and 8% Spandex so they are ultra soft, warm, comfortable and are perfect to wear at home for your indoor workout session or as an extra layer of warmth under your clothes when you brave the frigged winter chill outside.
The WuhouPro Women's Long-John Sets are made to fit well and are comfortable to wear under other clothes without a lot of shifting and bulking and bunching in uncomfortable places!
The bottom line is that the WuhouPro Women's Long-John Set is a great option for beginners and experienced runners alike who want an added layer of warm and comfortable protection for their wintertime runs!
10. Just Love 2-Piece Thermals
- Keeps cool when hot, warm when dry
- Overall good quality, making it great value for price
- Runs small accoding to some users
- Material is prone to stretching
Another great option for two-piece thermal underwear sets for women is the Just Love set. These thermals are made to be comfortable against the skin, easy to wear long term, and effective at trapping body heat.Read more
These base layers and thermal underwear are perfect for cold weather runs when you still want to get out for that run but the weather is a little less than ideal. The Just Love 2-Piece base layers and thermal underwear are basic in design but are easy to use and do exactly what they are meant to do!
While base layers and thermal underwear is not as stylish as some of the others on our list they are still a good choice for a cozy underlayer to wear under your running jacket and pants. Keep the shivers at bay and enjoy your runs even more with these weather resistant and insulating thermal underwear.
Made from a cotton and polyester blend, these thermals are made to last and will help fight back the bite of winter’s chill while you are out for a run or simply out running errands.
The Just Love 2-Piece Thermals are made to be a little on the looser side so they can function as the under later or a middle layer if you are getting really bundled up for an exceptionally cold run. Consider how you will use them to determine if you need a bigger size to accommodate an underlayer.
The bottom line is that the Just Love 2-Piece Thermals are a smart choice that any runner can take advantage of and benefit from using!
Criteria Used for Evaluation
It seems obvious that consumers should be looking for a base layer and thermal underwear that keeps the cold away.
How warm the clothing isn’t the only thing that matters when looking for the best item to purchase.
The price range varies among base layers and thermal underwear so it’s important that the consumer knows whether or not that they are buying a high-quality option. Sometimes this means investing in a more expensive item, but there are affordable options that still perform well - even though they might have to sacrifice on a few features.
The following criteria we used to find the best thermals are explained below.
First and foremost, the thermals should perform well when it comes to keeping the consumer warm.
What types of materials are used? Some fabric like merino wool is extremely warm, while spandex options may not cut it in freezing temperatures. How thick is the material? Is it midweight or heavyweight? Is it easy to layer?
While being warm is crucial, the last thing anyone wants is to be too hot. This causes sweating, meaning the consumer is wet and can get a chill. How breathable is the fabric? Does it offer ventilation like a zip down in the front to help regulate body temperature?
The materials used in these garments is an important feature that must be carefully considered.
Thermal layers are made from various materials, with the most popular being merino, polyester cotton, and even silk. Some may even feature blends of fabric to get the functionality of whatever that specific material has to offer.
Merino wool is the fan favorite material used for base layers. That’s because of how warm, yet breathable its fibers are. It is just as thick as synthetic fabric, yet warmer. But don’t think it will feel itchy like traditional wool. Instead, merino wool is soft on the skin. It is odor-resistant since it has natural antibacterial properties. It is the more expensive of the materials but is so worth it.
Polyester is also a popular material used. It is much less expensive than merino wool, while still being comfortable. It has moisture-wicking functionality and does a decent job of regulating body temperature.
Also affordable, cotton is warmer than polyester and soft. However, its main drawback is that it soaks up a sweat, so isn’t the warmest option for outdoor sports.
The general rule of thumb is the colder the weather, the tighter the underwear should fit.
A snug fit prevents air from reaching the skin. It serves as a second skin, so should fit as close to the body as possible without being uncomfortable.
The thickness of the layer will help determine how warm it will be. This is measured by insulation weight, g/m². Lightweight base layers usually fall around the 150g/m², whereas mid-weight thermals are about 250g/m².
Lightweight options are ideal for things like hiking and running where some warmth is needed, but the consumer still wants breathability. Midweight options are better for skiing and are versatile enough to even be worn as a top layer in warmer weather.
Of course, there are even heavier choices, but the consumer should not want to go too heavy to overheat depending on the weather and their activity.
Consider what you want and need and make sure you spend enough time looking at all the options available to you.
The type of thermal layers and thermal underwear we’re looking at includes shirts and leggings that are worn close to the body, acting like a second skin to protect you from the cold.
If you’re into winter sports like skiing, snowboarding, or hiking, or if you just like to keep up your running routine when the weather starts to turn you definitely need to invest in gear like this.
We’ve put together a selection of the best options out there to give you a place to start, whether you’re new to base layer clothing or you’re looking for something to replace your old gear. Check out our FAQ for info on sizing and materials, or take a look at our custom criteria to get a better idea for what makes our list the best of the best.
Expert Interviews & Opinions
Depending on the material used in your base layers, care instructions vary. For example silk materials should be hand washed or delicate cycle, synthetic fabrics dry quickly and are safe to wash in warm water. Wool should be washed in cold water and laid on a towel to air dry. Cotton materials should be washed in cold water and air dried on a towel.
Consider looking at a thermal base layer that has bacteria resistant properties. This will add in your clothing staying fresher longer.
Other Factors to Consider
All of the factors that have been discussed here in this buying guide are important and needs to be carefully considered as you shop around. It is also important to keep in mind that there are some things a consumer should know when shopping for thermals. It is our hope that you find the base layers and thermal underwear that are right for you and that will serve you well and keep you warm and comfortable while you are out and about this winter.
Frequently Asked Questions
q: What is the best material for a base layer?
Merino wool is arguably the best materials because it is super soft and comfort is its main selling point. It is also warm which is important but is more expensive. Other synthetic fabrics like polyester also work well.
q: How are thermal layers supposed to fit?
Base layer and thermal underwear are supposed to have a snug fit, as close to the skin as possible to keep the body warm. It is important to keep this in mind when sizing; many base layers will run small or have a slim fit to ensure they lay close to the body.
q: What temperature are these recommended for?
While the quality and overall performance vary among thermal underwear and base layers, all the options on this list are ideal to wear during winter and cooler temperatures. Just make sure to wear as a base or mid-layer for optimal warmth.
q: What does a moisture-wicking base layer mean?
A base layer with moisture-wicking properties means that the fabric pulls the moisture from the body to the outside of the shirt or pant where it evaporates more easily instead of being soaked within the fabric.
q: What is the best base layer for skiing?
Skiers should look for a midweight base layer with moisture-wicking for when they work up a sweat.
- How to Choose Long Underwear (Base Layers), Outdoor Consumer Website ,
- Power Stretch, Fabric Manufactuer Website ,
- How To Choose The Perfect Base Layers To Keep You Warm This Winter, News Website ,
- Man’s Guide To Buying Thermal Underwear | 5 Points To Consider When Purchasing Thermals, ,