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16 Best Thermal Underwear & Base Layers Tested & Reviewed

last updated: Mar 16, 2020
The best base layers and thermal underwear are going to keep you toasty and prevent sweat buildup. Fact: thermal base layers are not so well-kept secrets for those that love outdoor adventuring or that work in outdoor construction.

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

icon
Smartwool NTS Mid 250
98.8/100 our score
Breathability
99.8
Durability
99.6
Materials
99.7
Fit
99.2
Weight
98.9
Smartwool NTS Mid 250
Why is it better?
  • Warm, yet light
  • Very comfortable
  • Looks good on and feels even better on
  • Breathable
  • Great quality
In a Hurry? Editors choice:
Smartwool NTS Mid 250
Test Winner: Smartwool NTS Mid 250
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Researched Sources
4
Researched Sources
Reviews Considered
1.5k
Reviews Considered
Hours Researching
22
Hours Researching
Products Evaluated
16
Products Evaluated
Sorting Options
Breathability Durability Materials Fit Weight By Default
Rank
PictureProduct
Name
Rating
Shops
#1
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
98.8
Breathability
99.8 %
Durability
99.6 %
Materials
99.7 %
Fit
99.2 %
Weight
98.9 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#2
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
96.8
Breathability
98.9 %
Durability
98.8 %
Materials
97.3 %
Fit
96.9 %
Weight
95.8 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#3
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
96.2
Breathability
98.7 %
Durability
93.8 %
Materials
95 %
Fit
99 %
Weight
96 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#4
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
95.8
Breathability
97 %
Durability
93 %
Materials
98 %
Fit
92 %
Weight
99 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#5
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
95
Breathability
89 %
Durability
94 %
Materials
97 %
Fit
97.9 %
Weight
98.5 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#6
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
94
Breathability
96 %
Durability
89 %
Materials
92 %
Fit
98 %
Weight
95 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#7
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
93.8
Breathability
91 %
Durability
93 %
Materials
92.9 %
Fit
97 %
Weight
96 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#8
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
91.6
Breathability
86 %
Durability
91 %
Materials
90 %
Fit
95 %
Weight
96 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#9
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
90.8
Breathability
97 %
Durability
86 %
Materials
84 %
Fit
90 %
Weight
97 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#10
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
89.8
Breathability
87 %
Durability
89 %
Materials
90 %
Fit
91.5 %
Weight
92 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#11
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
88.2
Breathability
90 %
Durability
83 %
Materials
85 %
Fit
92 %
Weight
91 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#12
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
86
Breathability
89 %
Durability
85 %
Materials
89 %
Fit
84 %
Weight
83 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#13
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
85
Breathability
87 %
Durability
75 %
Materials
79 %
Fit
90 %
Weight
94 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#14
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
83.6
Breathability
81 %
Durability
92 %
Materials
91 %
Fit
71 %
Weight
83 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#15
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
78
Breathability
79 %
Durability
78 %
Materials
78 %
Fit
78 %
Weight
77 %
Price Comparison Last Updated (30.03.20)
Amazon Link
#16
The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
75
Breathability
77 %
Durability
75 %
Materials
75 %
Fit
73 %
Weight
75 %
Price Comparison Last Updated (30.03.20)
Amazon Link

16 Best Thermal Base Layers

1. Smartwool NTS Mid 250

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
98.8
Smartwool NTS Mid 250 Zip T
Amazon Link
Breathability
99.8
Durability
99.6
Materials
99.7
Fit
99.2
Weight
98.9
best offer for today
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Pros:
  • Warm, yet light
  • Very comfortable
  • Looks good on and feels even better on
  • Breathable
  • Great quality
Cons:
  • Expensive
  • 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.

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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.

2. Arcteryx RHO AR

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
96.8
Arcteryx RHO AR
Amazon Link
Breathability
98.9
Durability
98.8
Materials
97.3
Fit
96.9
Weight
95.8
best offer for today
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Pros:
  • Great for layering
  • Durable and comfortable
  • High collar and zip neck
Cons:
  • 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.

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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.

3. Under Armour 4.0

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
96.2
Under Armour 4.0
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Breathability
98.7
Durability
93.8
Materials
95
Fit
99
Weight
96
best offer for today
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Pros:

Thermal fleece for warmth

Thermal grid fabric

Quick Dry

Moisture-wicking

Prevents odor

Lightweight

Cons:

Expensive

The Under Armour 4.0 baselayer leggings are really warm and perfect for cold weather running. They are lightweight, moisture-wicking, and really comfortable--you will barely feel them there while you are running!

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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

heir 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.

4. Icebreaker Everyday

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
95.8
Icebreaker Everyday
Amazon Link
Breathability
97
Durability
93
Materials
98
Fit
92
Weight
99
best offer for today
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Pros:

Merino Wool

Moisture Wicking

Breathable and soft

More lightweight than other 100% Merino Wool layers

Close fit

Odor-resistant

Wear as a base layer or a top

Cons:

Runs small and short

Not much stretch

This Icebreaker model is perfect for everyday wear, as the name might suggest. It is 100% Merino wool but is more lightweight than most Merino wool options, so you can wear it under hiking gear, running clothes, or your office blues without having to worry about it being too bulky or uncomfortable.

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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.

5. CW-X Insulator Stabilyx Tights

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
95
CW-X Insulator Stabilyx Tights
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Breathability
89
Durability
94
Materials
97
Fit
97.9
Weight
98.5
best offer for today
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Pros:

Provides knee, hip, and back support

Keep heat well

Helps with pain

Can mitigate post run issues

Compression

Cons:

Can be difficult to put on

The CW-X Insulator Stabilyx Tights strengths are twofold, as it will support its wearer both by keeping them at optimum running temperature while providing them with all the stability an athlete will need. The Stabilyx tights are a perfect base layer for the runner in need of the extra support.

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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 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.

6. Tesla Compression

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
94
Tesla Compression
Amazon Link
Breathability
96
Durability
89
Materials
92
Fit
98
Weight
95
best offer for today
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Pros:

High-quality blend of materials

Compression fit

All-season wear

Moisture wicking

Affordable

Lots of colors to choose from

Good temperature regulation

Side and back mesh panels for ventilation

Sun protection UPF 50+

Cons:

Runs small

Tesla Mesh Compression is a very affordable option for runners who want something with good temperature regulation that isn’t thermal. The compression is a great feature that will help with circulation and muscle recovery, especially if your workouts are a little more diverse.

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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.

7. Helly Hansen

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
93.8
Helly Hansen
Amazon Link
Breathability
91
Durability
93
Materials
92.9
Fit
97
Weight
96
best offer for today
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Pros:

Lifa T3 insulation and cooling

Performance Merino Wool

Low bulk cuffs for easy layering

Cons:

Refer to size chart; fits snug some run a size up.

The right base layer is both high performing and great looking. It fits so well and functions so right that except for the fact that you’re warmer when you need to be and cooler when you should be, you forget you’re even wearing it. Meet the Helly Hansen HG Warm Ice!

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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.

8. CompressionZ

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
91.6
CompressionZ
Amazon Link
Breathability
86
Durability
91
Materials
90
Fit
95
Weight
96
best offer for today
Amazon Link
Pros:

Best compression fabrics

Wicking, breathable

Anti-odor technology

Cons:

Compression fit will run snug, see size chart

The CompressionZ Women’s Legging looks great every day for every type of activity. Couple these leggings with cute tops for dinner out, hoodies for evening neighborhood walks or your favorite workout gear when you’re serious about training. No matter how or where you wear these stylish bottoms, you’ll reap endless health and fitness benefits while looking beautiful.

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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.

9. Duofold Mid-Weight

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
90.8
Duofold Mid-Weight
Amazon Link
Breathability
97
Durability
86
Materials
84
Fit
90
Weight
97
best offer for today
Amazon Link
Pros:
  • Mid-weight and warm when layering
  • Quality fabric
  • Size runs true to fit
  • Very affordable
Cons:
  • 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.

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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.

10. Paradox Performance Merino

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
89.8
Paradox Performance Merino
Amazon Link
Breathability
87
Durability
89
Materials
90
Fit
91.5
Weight
92
best offer for today
Amazon Link
Pros:
  • Blend of materials including spandex and merino wool
  • Zipper pullover design
  • Affordable
  • Thumb holes on sleeves
  • Quick-dry
  • FreshGuard keeps odors away
  • Soft and comfortable
  • Helps regulate temperatures
  • Athletic fit
Cons:
  • 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.

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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.

11. Tesla Thermal

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
88.2
TSLA Men's Thermal
Amazon Link
Breathability
90
Durability
83
Materials
85
Fit
92
Weight
91
best offer for today
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Pros:
  • Great insulation
  • Fits well
  • Stylish
  • Affordable
Cons:
  • 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!

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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.

12. Minus33 Katmai Expedition

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
86
Minus33 Katmai Expedition
Minus33 Katmai Expedition
Minus33 Katmai Expedition
Amazon Link
Breathability
89
Durability
85
Materials
89
Fit
84
Weight
83
best offer for today
Amazon Link
Pros:

Great for Extreme cold

Fit snug

Move well

Hold heat

Breathe well

Soft to the skin Cuffs work well

Cons:

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.

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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,

13. Ekouaer

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
85
Ekouaer
Amazon Link
Breathability
87
Durability
75
Materials
79
Fit
90
Weight
94
best offer for today
Amazon Link
Pros:
  • Comes as a set of both underwear long sleeve shirt and pants
  • Soft and warm
  • Affordable
Cons:
  • 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.

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Construction

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.

14. Carhartt Base Force

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
83.6
Carhartt Base Force
Amazon Link
Breathability
81
Durability
92
Materials
91
Fit
71
Weight
83
best offer for today
Amazon Link
Pros:
  • Keep you warm in winter
  • Good quality and thick
  • Affordable price
Cons:
  • 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.

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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.

15. WuhouPro

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
78
WuhouPro Women's  Long-John Set
Amazon Link
Breathability
79
Durability
78
Materials
78
Fit
78
Weight
77
best offer for today
Amazon Link
Pros:

Protection from cold

Stretch for FIT and flexibility

Cons:

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!

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Use

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.

Weather Resistance

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.

Materials

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.

Fit

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!

Bottom Line

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!

16. Just Love 2-Piece Thermals

The rating is based on the average rating (1-100) from all the criteria in which we rated this product.
75
Just Love 2-Piece  Thermals
Amazon Link
Breathability
77
Durability
75
Materials
75
Fit
73
Weight
75
best offer for today
Amazon Link
Pros:
  • Keeps cool when hot, warm when dry
  • Overall good quality, making it great value for price
Cons:
  • 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.

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Use

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!

Weather Resistance

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.

Materials

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.

Fit

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.

Bottom Line

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

Breathability

Of course, when it comes to running, it’s not only about the running shoes. There are so many other variables to improve your endurance and overall workouts. A base layer is a prime example that can set you apart to become your best.

How warm the clothing isn’t the only thing that matters when looking for the best item to purchase.

There are some factors to consider when you’re looking to buy a new base layer. We don’t only look for the best and new base layers, we also look for the biggest trends and the best reviews. Breathability depends on many factors. It starts with the quality used in the products that allow for the right ventilation and thickness vs lightweight in the material.

A great example of a lightweight breathable material is the Merino Wool fabric. This fabric keeps away bad odors and keeps you warm, that’s why it’s best to use in cold climates. Other fabrics that offer great breathability are synthetic fabrics that offer wicking properties. This means that the base layers don’t really absorb the sweat, rather they transfer it away from your skin. Unlike other fabrics, this is best used in humid and wet climates

Durability

Another important factor that we take into consideration is how durable the base layer will be.

In order to save on cost and keep wearing the same base layer for a long time, we need to take into account the test of time. Merino Wool has been questioned because it is soft and will most likely develop holes with its usage. Therefore, it’s not as durable as the other fabrics.

It’s crucial to read the washing instructions as it will help you extend the gear's lifetime. This will allow you to ensure that the fabric remains intact and durable. Some manufacturers are mixing different fabrics together in order to get one product that is stronger. Of course, there are also some other variables such as how comfortable the product feels on the skin, the technology used and how these products are designed is what keeps them durable without compromising its quality.

Materials

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.

This defines the durability, breathability, and comfortability of the gear. The material is most likely what will keep you cool or warm, therefore, be careful and don’t pick your base layer based on a style by compromising the quality of the material. Merino Wool is usually the higher costs because of its ability to be soft and comfortable, it has superior temperature regulation and anti-odor ability, but it’s expensive and less durable than polyester.

Even though it is the most expensive, it is worth the buy. Then we have the blends. Manufacturers mix different materials to acquire the desired quality. Some brands like Arc’teryx and Patagonia provide a mix of materials and provide the comfort of merino wool and the long-lasting trait of polyester.

Fit

Base layers should fit more snuggly--hence the leggings and tighter shirts.

For the best performance, base layers must fit in tightly which will help the material to pull the moisture from your skin. Some people like to use it as an additional layer and that makes the product less functional. Consider getting a base layer that fits in tightly and avoids looking at the style because of looks.

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. Make sure to size accordingly and plan ahead base on how you plan to layer up as well as the weather you are in.

Weight

When measuring the warmth of a base layer, consider its weight.

There are different types of weight – lightweight mid-weight and the heavyweight. Depending on your level of activity and different times of seasons will determine what type of base layer you will need. Lightweight is the best for breathability, for example, however, it does not allow you to stay warm.

If you’re looking to stay warm and use a base layer in colder climates, then you might consider the Merino Wool fabric as it offers a great deal of temperature control. Mid-weight is right in the middle. It has just enough weight for the cold weather and also breathable quality for the hot, summer months.

Be prepared and make sure you have everything covered. You might want to get one of each in order to be prepared.

Expert Interviews & Opinions

Most Important Criteria (According to our experts opinion)
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Proper care is essential.

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.

Going on trip off the grid?

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

Features

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.

Weather Resistance

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?

Bottom Line

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.

Frequently Asked Questions

q: What is the best material for a base layer?

a:

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?

a:

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?

a:

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:

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?

a:

Skiers should look for a midweight base layer with moisture-wicking for when they work up a sweat.

q: Which is the best anti-odor base layer?

a:

The best factor in avoiding odor is choosing the right material. Merino wool is one of the best fabrics available for this purpose. It pulls sweat away from the body and allows for proper ventilation which will limit the build-up of the bacteria that cause body odor.

q: How does a base layer regulate your body's temperature?

a:

A proper base layer is both moisture resistant and well ventilated. Keeping you dry when its cold will allow your body to more easily regulate its body temperature. Proper ventilation and air flow will allow your body to only keep the heat it needs and remain cool in excesses of that. A well-made base layer can easily accomplish both of these goals and be useful to a runner year round.

The fabric best suited for quality construction, moisture management, and temperature regulation is merino wool. This is the material we would recommend for your base layer, no matter the season.