18 Best Thermal Underwear & Base Layers Tested & Reviewed

Material

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.

Breathability

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.

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.

Value

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.

Construction

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.

Breathability

These are moisture-wicking and dry quickly--and their odor prevention tech will ensure your tights stay smelling fresh.

Durability

These are really expensive but they are perfect for those of you who need something that will keep you warm during all of your runs. They are durable and, while they don't have any reflective features, they are the perfect base layer for you serious runners out there.

Fit

Their quick-dry construction will help keep you cool and dry and their 4-way stretch ensures full range of motion.

Weight

No matter how much you layer, you will find that this base layer is really lightweight and won't retain sweat, so they won't get soaked and weigh you down.

Materials

These leggings are made of 100% polyester and their thermal grid fabric will keep you warm.

Breathability

The fantastic Merino wool content of this base layer means that you’ll stay warm without overheating or dealing with excess sweat. Merino wool naturally wicks moisture and is ultra-breathable, as well as odor-resistant.

Compared to other base layers made with Merino wool, this one is very thin and lightweight, so you can wear it under practically anything or as a sheer top over a camisole or sports bra. It’s the perfect layer for if you just need a little bit more warmth and coverage without needing a heavy-duty undershirt.

Durability

If you can afford to invest in this base layer, you will find that it is worth every penny. Not only is it lightweight and effective, but it is also incredibly durable. The materials it uses and the construction ensures that it is reinforced in all of the right areas.

Fit

When it comes to fit, this base layer fits snuggly and tightly. It is easy to layer this one because it is not bulky. Since it is so lightweight and thin, this is the perfect base layer for those of you who get cold and need to add more.

Weight

As far as the weight of this base layer, this one is incredibly lightweight. Since it has moisture-wicking properties, you will also find that this base layer won't weigh you down if you sweat a little or get wet.
Materials

Made with 100% Merino wool, it is soft and comfortable as well as non-itch. The neckline is accommodating to whatever you may want to wear over the layer and will allow room to move and breathe if you’re active. The fit is slim so it isn’t bulky or hard to wear underneath other tops, but it also runs a bit small and short.

Also, the material isn’t blended with any spandex or Lycra so it doesn’t have a lot of stretch and may easily lose its shape if stretched out.

Breathability

The Stabilyx tights are much more known for keeping in their heat over their warm weather wear. They are also remarked on having remarkable compression, preventing muscle pain and fatigue after extended activity.

Another attribute of note is these leggings provide knee support and stability, so issues with injury, recovery, or problems with chronic leg conditions can be mitigated by the CW-Xs support web. The Stabilyx also sports a support panel to help with abdominal and lower back support.

Durability

These are on very high end as far as prices go for tights, but they deliver on their price in both product quality and performance. If you are looking for a year-round base layer, the CW-X Insulator Stabilyx Tights may not be a perfect fit, as they tend to keep a runner pretty warm.

They are a remarkable pair of tights in that the support and compression they provide makes them very valuable to the runner who needs that specific type of gear: If they fit your niche, they are well worth the cost.

Fit

These running tights are made seamlessly to optimized wearer comfort and prevent and abrasiveness and discomfort that the repetitive motion can cause. Now the one negative with the Stabilyx Tights that a lot of wearers warned about is that they can sometimes be very difficult to put on.

Weight

When we took a look at the overall weight of this base layer, we found that despite how much warmth they provide they are still really lightweight. If you need to travel you will find that these pack light and when you run or workout in them you will find that they are great at wicking away moisture.

Materials

The general consensus is that once they are on, though, they perform more than satisfactorily. The CW-X Insulator Stabilyx Tights are made from 80% Coolmax and 20% lycra.

Breathability

The material blend is great for wicking moisture away and there are mesh panels for ventilation in the back and sides, keeping you cool and dry. It does offer a little more warmth when layered with other gear, but it’s a better choice for temperature regulation while running in any season than to keep warm while doing things like hiking and skiing. It also will help keep you protected from UV rays with UPF 50+.

Durability

This base layer is made of high-quality material that many other base layers use as well. It is really durable and built to last--so you can keep it around for many seasons to come.

Fit

Customers expressed dissatisfaction with the fit and not often did they all have the same complaint. Some said it was too long while others said the sleeves were too short, some expressed it didn’t have enough compression and others complained it was too tight to wear. The issues are inconsistent and wide-spread, but this inconsistency may mean that they are outliers for an otherwise useful product that many others loved.

Weight

It does offer a little more warmth when layered with other gear, but it’s a better choice for temperature regulation while running in any season than to keep warm while doing things like hiking and skiing. It also will help keep you protected from UV rays with UPF 50+.

Materials

The material make-up is 87% polyester and 13% spandex for a great combination of elasticity and function. The fit is unfortunately where this base layer falls short.

Breathability

The lean design and low bulk cuffs make throwing your layers over easy-breezy. Flatlock stitching adds essential smoothness with anti-chafing and less irritation. With warm wool and wicking properties together, you’ve found your perfect long sleeve base layer!

Durability

This is the solution for you, functions are wide and regulate temperature at any given time provides insulation and drying capabilities while simultaneously forgetting you’re wearing it at all.mmIf you are an all-weather runner we have what you are looking for, one that can keep you warm when need be and can also help you cool down when there is need to due to its thermoregulatory function.

Fit

This wool base layer is available in 18 colors and dual tones, each as sleek as the next - Black with Flag Red and Racer Blue with Evening Blue are exceptional. Sophisticated technologies contrasted with a classic design fuse to create a high functioning, aesthetically pleasing base layer.

Flatlock stitching and low-bulk cuffs mean comfortable fabrics and fit next to the skin. You need your base layer to work for you and look great, while simultaneously forgetting you're wearing it at all. With the NH Warm Ice, mission accomplished!

Weight

The best part about this base layer is that it is really lightweight! Since it doesn't absorb sweat, you won't have to worry about it weighing you down either.

Materials

Coupling merino wool with 43% polypropylene makes for an excellent fabric that thermoregulates and feels right next to the skin while also providing both insulation and drying capacities. Patented Lifa T3 hollow fiber engineering keeps athletes even warmer during hardcore workouts in the coldest climates.

Breathability

The patented Smart Moisture Management system eliminates moisture and sweat and protects the body from chafing and abrasions or irritation. We love the antibacterial/anti-odor technology fused into the fabric.

Durability

When you don’t have time to shower between the gym and lunch, you don’t have to worry - between the microbial protective system and the wicking fabric, you’ll feel fresh and ready for anything.

Fit

We love the on-trend appearance of these sleek compression leggings. They fit snug in all the right places, offering excellent support and an attractive fit. With go-to, all-occasion capability, the CompressionZ Leggings are certain to be a favorite. Reasonably priced, we’re pretty sure you’ll want one in each color (nine, to be exact)!

Choose Leopard Blue to appease your wild side or sophisticated Ferns Silver for day outings that transition into a night at the gym. With odor free fabric, not only are they the perfect “everything” pant, you’ll love the way you can wear them from gym to park-and-play to dinner without missing a beat!

Weight

Average priced, but this pant does its duty as your go-to fashion legging and compression gear. Well worth it! The pants stand on their own hence eliminating the need to buy other compression clothing. Quite amazing as it provides just the boost that your lower half needs and craves for.

We have to admit that not everyone likes to put on shorts, reasons best known by them that is why we feel that this compression pants will be your go to. They act as support on your lower half eliminating the need to shop for a number of compression clothing, they are a perfect choice since they also have a number of advantages with them.

Materials

Sit back and relax - this may take awhile. The CompressionZ Legging helps to reduce unwanted muscle motion during runs or hard workouts. This assists in energy waste-reduction, ultimately improving your workout and stamina. The compression fabric also works to improve circulation and reduce muscle fatigue and pain during and after your training.

This helps athletes to feel less soreness even days after strenuous workouts, too. The patented Smart Moisture Management system eliminates moisture and sweat and protects the body from chafing and abrasions or irritation.

Material

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.

Breathability

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.

Fit

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.

Construction

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.

Use

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.

Weather Resistance

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!

Materials

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.

Fit

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.

Bottom Line

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.

Material

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.

Breathability

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.

Fit

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.

Value

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,

Construction

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.

Materials

Omni-HEat thermal reflective lining incorporated into the fabric increases overall warmth you can retain throughout the body. It is a versatile product that works very well on its own or as a layer underneath other clothing. The fabric is treated with anti-odor technology to keep you fresh.

Weight

This is a great product of the most active people who enjoy exercising outdoors in all weather, even extreme cold. Runners, hikers, rock climbers, and the avid skier can gain a lot of heat with the heat entrapment technology this top provides.

Fit

You will spend a couple of bucks on this top but it has an incredible ability to retain heat, which is what you want on chilly days. It can work well for an average workout as well as benefit you on the slopes. It is a great piece of clothing to have in your closet that you can use whenever you will be in cooler temperatures.

Materials

The coldest days to the best with layers, and having a layer that will lay on the skin without sliding or bunching up and one that won’t add extra bulk makes it a great product that will work with almost any top clothing. The breathability will help your skin stay dry and also keep in the warmth close to your skin.

Weight

This shirt is light but still makes an ideal under layer for those cold days

Fit

This top fits like a second skin so it will easily fit as a base layer under pretty much any type of clothing. Even though it provides a close fit it doesn’t feel restrictive at all. It also has plenty of stretches so you will have no problem with the range of motion or movement. This is a very soft to that has excellent moisture wicking abilities.

Materials

The cotton two-layer engineering is really something. It is set up to trap your natural body heat between the layers. You effectively act as your own furnace. This allows the outer portion of the pant to shield from the cold while the inner portion is circulating warm air. The polyester textile will do it’s magic keeping the pant very strong, almost tear resistant, and will help it hold its shape as it isn’t a fabric that is prone to shrinkage.

Weight

The tagless labeling is a thoughtful feature that will allow this product to sit well on your body without any annoying itching or irritation from a flapping piece of fabric

Fit

The front and back rise gives a great amount of coverage and very smooth wearing when you are engaged in outdoor activity. The front fly is another practical feature.

Materials

This product is naturally perfect. Merino wool is breathability and can help with moisture management, it is a four-season fiber as it can keep you incredibly warm while also maintain your coolness, it is odor resistant as well as strong, and this is all in its natural makeup. It is amazingly soft as well, beating out the cliche of itchiness when one thinks of the feel of wool.

Weight

this baselayer offers such tremendous functionality as mentioned above due to this special, natural material, it also offers a rating of UPF 50+ so that it can protect your skin from intense sun rays, especially those that are magnified by reflecting off of crystalline white snow.

Fit

Literally, there aren’t any sizes that are not covered by this brand. The smallest XS to the largest 6XL can go out with protection. When you need to wash your product, this one will be cleaned with ease. It is safe to use in the machine to wash and it will dry well. This is a product that can be used in three seasons, making it very useful for a wide variety of outdoor activities that require a solid base layer.

Materials

A very important feature about this product especially for those that are going out in the wilderness for some time and need to pack light, pack smart, and not have access to amenities for some time, these are going to serve you well. They can actually last for a couple of days on without developing a build-up of odor making yourself a bit too ‘ripe’ for others or yourself

Weight

In addition, if you find yourself sweating, these won’t keep that moisture in making your skin clammy, they will wick it away and dry quickly so you can maintain a comfortable feel and dryness that will aid in containing essential warmth.

Fit

This Is a product that will move with you, handle the elements, and legit keep you set with temperature regulation and comfort for days should you need to use them on a long term basis like that. This makes these an ideal pair for hunters or especially for through hikers that go on long hikes with stops for quick camps where packing light and effectively is most essential.