10 Best Men’s Thermal Underwear that’s Ultra Warm & Light

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best thermal underwear for men

Anyone who lives in a colder climate understands the struggle. You break out your warmest clothing and hope you can keep winter’s sometimes endless chill at bay.

And, hopefully, your wardrobe includes thermal underwear that keeps you toasty and protected from freezing temperatures. The best thermal underwear for men, which we’ll review here, can make all the difference to your winter comfort level.

We’ll review the best thermal underwear for 2020, including our favorite – the Minus33 Kancamagus Midweight Bottom – offer some tips for how to wear them, examine the different types of thermal underwear, and other relevant information.

Quick Summary

bb2-table__imageMinus 33 Wool Kancamagus Midweight Bottom
  • 1-year warranty
  • Suitable for any outdoor activities, even sports
  • Can be washed and dried in a machine
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bb2-table__imageTani SilkCut Thermal Underwear Set For Men
  • Great Durability
  • Micro modal fiber
  • No itchiness
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bb2-table__imageDuofold Mid-weight Double Layer Thermal Union Suit
  • Tagless neck design
  • Comfortable fit that keeps you warm
  • Suitable for moderate activities
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bb2-table__imageThermajohn Ultra-soft Thermal Underwear Long Johns Set
  • Comfortable
  • Great body movement and flexibility
  • Designed with materials that don't bunch up
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bb2-table__imageCarhartt Men’s Force Midweight Classic Thermal Base Layer Pant
  • Carhartt's fast-dry technology
  • Excellent for outdoor work
  • Maximum comfort due to its strategically-placed seams
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bb2-table__imageHanes Waffle Knit Thermal Pant With Fresh IQ
  • Shrinkage-controlled underwear
  • Sturdy seam construction that offers durability
  • Buy next larger size for looser fit
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bb2-table__imageSmartwool Base Layer Top (Merino 150 Wool)
  • UPF 30 sun protection
  • Breathable and quickly dryable materials
  • Not very tight on shoulders and back muscles
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bb2-table__imageRocky Thermal Underwear Long John Set
  • Great for layering
  • Comfortable due to its elastic waistband
  • Warm and lightweight
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bb2-table__imageTSLA Men’s Thermal Microfiber Soft Fleece Longjohns Set
  • Stylish slim-fit design
  • Great ease of movement adjusted to your body
  • Double-stitched neckline offers a nice fit
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bb2-table__imageColdpruf Basic Dual-layer Bottom
  • Great for base layering
  • The two-layered cotton/polyester keeps the body warm
  • The Merino wool provides great movement while retaining its shape
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Before you buy: 7 Things to consider when purchasing thermal underwear

The last thing you need in the dead of winter is a pair of thermal underwear that doesn’t fit, doesn’t feel right, or doesn’t keep you warm enough. And what fits and feels right for another man may not have the same fit and feel for you.

Here are some things to keep in mind when you’re buying thermal underwear, and to help ensure you find a pair that best suits you:

1. The fit

Never disregard the fit when purchasing thermal underwear. While a pair may keep you warm and cozy when the temperatures plummet, you probably won’t wear them as much as you should if the fit isn’t right.

A poor-fitting pair of thermal underwear typically distributes the warmth unevenly, i.e., there will be areas of warmth (even excessive warmth) and areas where there isn’t much heat at all.

In cold weather, a snug fit is ideal because it traps the heat generated by your body and boosts overall comfort. Thermal underwear should function as a second skin that creates a comfortable layer between the fabric and your body.

On the other hand, you don’t want a fit that’s too snug; in that case, you probably want to choose the next size up.

2. Breathability

Thermal clothing needs to breathe, which refers to its ability to let moisture out but also to prevent you from becoming over-heated. It should keep cold air out while distributing warmth evenly.

3. Material

Most thermal underwear consists of polyester, or a blend of polyester and cotton (and, sometimes, spandex).

However, more expensive brands often feature Merino wool – which is sheep wool that is warm, moisture-wicking, and which even has odor-reducing properties.

Synthetic thermal underwear fabric is ideal for extreme cold weather and, as mentioned, is often polyester and spandex, but also lycra and nylon. These materials offer a nice balance of moisture-wicking and heat-retention.

Silk is a lightweight fabric option that’s suitable for when the weather is cool but not very cold. It has a soft texture without a lot of bulk, but it’s not as good for drawing moisture away from the body quickly.

Cotton is soft and affordable, but it retains moisture more than other fabrics used in the construction of thermal underwear.

4.  Moisture-wicking

Many men rely on thermal underwear to help keep them warm during outdoor activities such as skiing or snowboard.

You can work up a sweat during those activities, however, which makes it crucial that you find a pair of thermal underwear that keeps you dry as you perspire.

Choose a pair of thermal underwear that does a superior job of wicking moisture away from the skin. A base layer – such as thermal underwear – won’t keep you nearly as warm when you’re wet with sweat, and you’ll lose heat quicker during the rest phase.

5. Function

Consider the reasons why you need thermal underwear before buying.

Will you need it for everyday use, such as to keep you warm during those moments when you happen to be outside? Or, do you need it for outdoor activities, such as skiing or snowmobiling, or if you work outdoors in the winter?

Keep the weight of the fabric in mind as you choose a pair of thermal underwear based on your activity. The weight determines the level of warmth the underwear provides.

6. Styles

Thermal underwear comes in a variety of styles – from a one-piece suit to two pieces bought separately (but perhaps as part of a set).

You can also purchase thermal underwear in a variety of colors. thermal underwear is meant to wear under other clothing, so its color may not be that important to you.

7. Care

Pay close attention to the care instructions that come with your thermal underwear.

Synthetic fabrics require simple care, for the most part. You can machine wash them, they’re dryer-safe, and they’ll maintain their original shape.

You’ll want to wash cotton blends in cold water to prevent shrinkage. Cotton takes longer to dry, and you’ll get the best results if you air-dry them. You can care for wool blends the same way.

It’s best to machine-wash silk blends, or you can machine-wash them on a delicate cycle.

The 10 best thermal underwear for men in 2020

1. Minus 33 Wool Kancamagus Midweight Bottom

Minus 33 Wool Kancamagus Midweight Bottom

Best features:

  • Exceptional warmth
  • Nice fit
  • Breathable

The best thermal underwear for:

Men looking for the best thermal underwear for extreme cold


There are plenty of contenders for the title of the warmest thermal underwear. But one that rises to the top is Minus 33’s Merino Wool Kancamagus Midweight pant; it’s warm enough to wear when temperatures fall below 0°.

The Kancamagus is toasty thanks, in part, to its 100% Merino wool construction. Gathered from the wool of Merino sheep, it’s among the finest, most comfortable wool in the world.

Many types of warmest thermal underwear for extreme cold feature Merino wool construction and, as the folks at Minus 33 put it, their midweight pant combines the “warmth of a blanket with the functionality of a pant.”

Those are helpful attributes when you spend a lot of time outdoors in the cold, or even for when you don’t spend much time outside but temperatures have dipped to single digits.

But the Kanamagus Midweight pant isn’t so warm that you can’t wear it in warmer temperatures, because it’s a three-season thermal bottom that many men consider an essential part of their outdoor gear.

The Midweight pant isn’t itchy like some wool garments either, and you have a variety of sizes from which to choose. While they may shrink just a tad in warm water, they’re stretchy enough to maintain a regular fit.


  • It’s suitable for a variety of activities, including sports and outdoor work.
  • Minus 33 offers a 1-year warranty that covers material and manufacturing defects.
  • The Merino wool is machine washable and dryable.


  • Some reviewers say the stitching could be more durable.

Bottom line

If you want to remain warm and comfortable in the coldest weather, you need a layer of clothing provided by garments such as the Minus 33 Kancamagus Midweight Bottom.

2. Tani SilkCut Thermal Underwear Set For Men 

Tani SilkCut Thermal Underwear Set For Men

Best features:

  • Micro modal fabric
  • Natural, biodegradable materials
  • Highly elastic and comfortable

The best thermal underwear for:

Supreme comfort and ethical contentment


Micro modal Air is a specialized type of fabric that is unusually soft and resists shrinkage extremely well. Given the obvious benefits of such a fabric, it’s hardly a surprise Tani loves to shout from the rooftops that their SilkCut Thermal Underwear Set is the only thermal underwear on the market that’s made from it.

The reality is, that isn’t just marketing hype: the fabric really is finer than silk and just as soft as you might imagine. But it’s also incredibly durable, resilient and brilliantly cosy, making you feel wrapped up and safe at all times.

This is because the good people at Tani have mixed in a good bit of Elastane in with the Micro Modal Air fabric (6% and 94%, respectively), to ensure you can move about as much as you like whilst staying warm, comfortable and safe.

It’s great for any kind of outdoor activity in cold climes. But it’s also a great luxury product to wear to bed or just around the house during the colder months.

Shockingly, given its luxury, Tani have also ensured that their thermal underwear is produced ethically, and is fully biodegradable, leaving you with a clean conscious as well!


  • Believe the hype – micro modal fiber is as warm, soft and cosy a fabric as you can find.
  • The price is offset by its brilliant durability
  • No itchiness and adjustment will be needed!


  • Sizing is not standard – be aware before you buy!

Bottom line

Tani have made some of the absolutely thermal underwear you will find, with unbeatable softness that is kind to your most sensitive parts.

3. Duofold Mid-weight Double Layer Thermal Union Suit

Duofold Mid-weight Double Layer Thermal Union Suit

Best features:

  • Provides excellent warmth
  • Excellent insulation
  • Stretchy

The best thermal underwear for:

For hunters and outdoorsmen


Warmth and mobility are a must for any many who engages in outdoor activities. Duofold has that in mind with its mid-weight double-layer thermal suit, which keeps you warm while allowing for a full range of movement.

That makes it among the best thermal underwear for hunters who, while often spending a lot of time remaining still, are frequently on the move, as well. They need a layer that keeps them warm but also offers an excellent fit and breathability.

The inside layer of the Duofold Union Suit consists of 100% cotton, while the outer layer features a blend of cotton, Merino wool, and nylon. The two layers offer excellent comfort and insulation and keep you warm in all temperatures.

The Union Suit features a long-sleeve coverall design with a full-button placket and a tagless crew neckline.


  • It keeps you warm without restricting mobility and movement.
  • Tagless neck design contributes to its overall comfort.
  • It’s excellent for a wide variety of low-impact activities.


  • It does shrink a little, so size accordingly.

Bottom line

The Duofold Union Suit combines the softness of cotton with the natural warmth of Merino wool to provide excellent thermal insulation in colder temperatures. It’s also the best thermal underwear for hunting.

4. Thermajohn Ultra-soft Thermal Underwear Long Johns Set

Thermajohn Ultra-soft Thermal Underwear Long Johns Set

Best features:

  • Lightweight
  • Odor control
  • Stretchable

The best thermal underwear for:

Men looking for a warm, stretchable set of long johns.


Thermal underwear has to keep you warm – if it doesn’t, what’s the point? But that doesn’t mean you must sacrifice comfort for warmth, either.

Thermajohn’s thermal long johns offer an excellent example of how warmth and comfort can mesh seamlessly in lightweight thermal underwear that gets the job done.

Made from a poly-spandex material, the Thermajohn long underwear is decidedly lightweight, stretches easily, and offers full mobility no matter what your activity. It fits snug – almost like a second skin – but is soft.

The poly-spandex material works to wick away moisture while keeping you dry even during heavy activity. The long johns also have smart odor control that prevents the spread of smells and absorbs odor-causing enzymes, so they don’t stick to the skin.

You’ll also love the flexibility of these long johns. You’ll enjoy full mobility, and the fabric doesn’t hinder your movements, whether you’re outside, at home, or in the office.

Other essential features include:

  • They feature a fly opening that’s convenient for whenever nature calls.
  • They have a flexible waistband that stretches with your body as you move and won’t dig into your midsection.
  • They don’t have tags, which can cause skin irritation.

Thermaljohn’s long johns are also durable with strong seams that won’t rip or tear prematurely.


  • A unique construction pattern offers natural flexibility and body movement.
  • You can wear them for any activity comfortably.
  • You don’t have to worry about the material bunching up and becoming uncomfortable.


  • Check sizing carefully – they may run small.

Bottom line

There’s a lot to love about Thermaljohn’s long johns – from their breathability and comfort to their durability.

5. Carhartt Men’s Force Midweight Classic Thermal Base Layer Pant

Carhartt Men’s Force Midweight Classic Thermal Base Layer Pant

Best features:

  • Flexible
  • Moisture-wicking
  • Enhanced comfort

The best thermal underwear for:

Men who work outside


Carhartt built its brand name on the strength of its durable, rugged workwear. They make more than just that these days, but products such as their men’s Force Midweight Classic Thermal Base Layer Pant take you back to the company’s roots.

While the Force Midweight Classic Thermal pants are suitable for men of all walks of life, they’re ideal for anyone involved with physical labor. They’re among the best thermal underwear for construction workers, for one, and great for anyone who works outdoors.

The Force Midweight pants consist of 100% polyester that offers easy flexibility without hindering movement. They follow your body’s natural movements instead of going against them.

Their waffle-knit design traps heat nicely and wicks moisture away from the skin. It’s also fast-drying and fights odor.

You’ll love the comfortable feel of these thermal pants, as well. As mentioned, the material flexes along with your body’s natural movements, while smooth flat-lock seams – along with a tagless label – enhance comfort.

There’s also a concealed, low-stitch waistband and contoured front for further comfort.


  • Strategically-placed seams offer maximum comfort and reduced chafing.
  • Carhartt’s fast-dry technology wicks away sweat and fights odor.
  • Their rugged design makes them excellent for outdoor work.


  • Sizing may run small.

Bottom line

Men who work outdoors in the winter need thermal underwear that’s warm and rugged enough to keep up with the demands of their job. Carhartt’s Force Midweight Thermal Base Layer pants do that and more.

6. Hanes Waffle Knit Thermal Pant With Fresh IQ

Hanes Waffle Knit Thermal Pant With Fresh IQ

Best features:

  • X-Temp technology
  • FreshIQ technology
  • Moisture control

The best thermal underwear:

For anyone who loves the Hanes brand


As advertising jingles go, the Hanes “Makes you feel good all under” was about as memorable as it got several decades ago. But it wasn’t just idle talk.

Hanes does make comfortable undergarments, after all, including comfortable thermal underwear. Their Waffle-Knit Thermal Pant with Fresh IQ features innovative technology that helps protect against colder temperatures, among other things.

Made from a 60-40 blend of cotton and polyester, the Waffle-Knit Thermal Pant responds to changes in your environment while helping to maintain a more optimal temperature. You’ll stay warm, but you won’t overheat.

With Fresh IQ technology, they also offer advanced odor protection, while the soft waffle-knit thermal knit fabric enhances comfort and warmth.

You can also buy a thermal top to go with the pants. You’ll enjoy the same technology and comfort (and odor protection) while enjoying a fit that follows your natural movements. It features flat, no-rub seams, as well as a stretchy neckline and ribbed cuffs.


  • Both the pants and shirt feature sturdy seam construction for excellent durability.
  • Hanes’s thermal underwear is shrinkage-controlled to retain its size and shape.
  • They fit snugly, but you can buy the next size larger for a looser fit.


  • Material is a little thin for some customers.

Bottom line

Hanes packs a lot of technology in their Waffle-Knit Thermal Pants to ensure that wearers get all the comfort and warmth they need. The Thermal Pants feature a soft, breathable fit.

7. Smartwool Base Layer Top (Merino 150 Wool)

Smartwool Base Layer Top (Merino 150 Wool)

Best features:

  • Excellent comfort
  • Great fit
  • Warm

The best thermal underwear for:

Men looking for a quality base layer top


The Smartwool company philosophy focuses on the idea that people need to spend as much time outside as possible. Moreover, they should be comfortable in the great outdoors, even when the temperatures make you shiver.

Their Merino 150 Wool Base Layer Top is made for outdoor living (in the winter, that is) and keeps you warm and comfortable, just as you’d expect from wool thermal underwear.

It features targeted insulation and ventilation and moisture-wicking technology that keeps you warm and dry without overheating you.

The Base Layer Top consists of a blend of 87% Merino wool and 13% nylon. The top has an interlocking knit that enhances breathability, comfort, temperature regulation, as well as odor resistance.

It’s also designed in a way that minimizes chafing. You can wear it under your snow jacket and enjoy a long day of skiing or another favorite outdoor activity.

While it features a slim-fit design, the Base Layer Top suits a variety of shapes and heights. Its long sleeves keep your wrists covered while it’s overall length helps ensure that it doesn’t ride up your back during activities.

You’ll also appreciate how lightweight this shirt is, yet also how it keeps you plenty warm even with its lightweight nature.


  • It’s very breathable and wicks away sweat while also drying very quickly considering its wool base.
  • It even features UPF 30 sun protection so you can wear it by itself on sunnier, warmer days.
  • It doesn’t cling to the shoulder or back muscles.


  • Some wearers didn’t like the nylon blend.

Bottom line

A breathable, comfortable thermal top is essential if you spend a lot of time outdoors – especially while engaged in active living. The Smartwool Men’s Base Layer Top has what you need to stay warm and comfortable when the temperatures fall.

8. Rocky Thermal Underwear Long John Set

Rockey Thermal Underwear Long John Set

Best features:

  • Soft interior
  • Moisture-wicking
  • Good elasticity

The best thermal underwear for:

Men looking for a versatile two-piece thermal underwear set


The Rocky Thermal Underwear Long John Set is an Amazon bestseller with over 1,500 primarily positive reviews. The Rocky company is doing something right, it seems.

And there’s a lot of love about this 2-piece thermal underwear set. It features a cotton/polyester blend, and the midweight and heavier weight versions include spandex for excellent stretch and flexibility.

The cotton/polyester fabric does a great job of wicking moisture away from the skin. It helps to keep you dry no matter what your activity, including jogging and other forms of outdoor workouts.

The overall fit of this 2-piece set is lightweight and snug. Not that it fits tight, but it fits snug enough against the body that it doesn’t appear obvious that you’re wearing anything under your regular clothing.

The shirt and pants also don’t lose their elasticity or shape over time; combined with their overall durability, you should get plenty of use from this set before its time to buy another one.


  • The long john pants feature an elastic waistband for ideal comfort.
  • They work well as a thermal or base layer.
  • It has a lightweight feel but offers plenty of warmth.


  • Sizing runs small

Bottom line

A lightweight set of thermal underwear that keeps you warm without adding bulkiness is always a plus. Rocky offers that and more with its 2-piece set.

9. TSLA Men’s Thermal Microfiber Soft Fleece Longjohns Set


TSLA Men’s Thermal Microfiber Soft Fleece Longjohns Set

Best features:

  • Flexible feel
  • Warm
  • Insulated

The best thermal underwear for:

Men looking for an affordable, basic thermal underwear set


The TSLA thermal underwear set is casual-yet-sporty, affordable, and also great for keeping you warm and comfortable for when winter creeps into town.

Made from fleece microfiber and spandex, the TNSLA top and bottom set provides a level of flexibility that’s hard to beat. It has a 4-way stretch and fits snug to the skin, yet it moves naturally with your body’s movements.

You’ll enjoy excellent mobility no matter what your activity, while its sleek design and color options mean you can even wear the top by itself.

The fabric is of a high density and not only provides exceptional comfort but maintains its original shape even after long-term wear.

It also helps wick moisture from the skin to keep you dry and comfortable while providing all the thermal insulation you need to handle those cold winter days and nights.


  • It provides excellent mobility and adjusts to your body’s movements.
  • Sleek, slim-fit design.
  • It includes a double-stitched neckline that offers a nice fit and flexible movement.


  • Sizing runs small.

Bottom line

The TSLA thermal underwear set is an excellent all-around investment that offers the warmth and comfort you need during the long winters.

10. Coldpruf Basic Dual-layer Bottom

Coldpruf Basic Dual-layer Bottom

Best features:

  • Two-layer protection
  • Odor protection
  • Tagless labeling

The best thermal underwear for:

Men who maintain low to medium-activity levels outdoors


ColdPruf has a century’s worth of experience in designing and producing products that keep its customers warm and comfortable from “chair lift to campfire.”

Their experience and know-how are apparent in products such as their men’s basic dual-layer bottom.

ColdPruf says the latter works perfectly fine as a base layer – i.e., with nothing worn under it – but you’ll appreciate its warmth and comfort no matter how you choose to wear it.

You’ll also appreciate its many exceptional features, such as:

  • ColdPruf’s technical fiber with Silvadur Intelligent Freshness that minimizes odor and odor-causing bacteria.
  • The ColdPruf ThermaChoice System that finds the right balance between what the weather is like and how your body reacts to the weather.
  • The Basic Dual-Layer’s construction includes Merino wool, which sets a very high standard for warmth and durability.
  • Tagless labeling and a non-itch waistband that enhances its overall comfort.

Speaking of the waistband, it rests comfortably at the natural waistline, while a front and back rise helps create an ideal fit while keeping the skin covered at all times. There’s also a convenient front fly for when nature calls.


  • The soft, cotton/polyester two-layer labeling traps body heat to block the chill.
  • The Merino wool follows your natural body movements while stretching and retaining its shape.
  • It’s ideal as a base layer if you choose to wear it that way.


  • The seam around the ankle is a little tight.

Bottom line

The Basic Dual Layer Bottom is an excellent base layer or as a thermal layer. It traps heat and while providing a cold-proof barrier.

8 Tips for wearing thermal underwear the right way

While there’s nothing overly complicated about the how, when, and why of wearing thermal underwear, there are some useful suggestions for doing so, nonetheless.

1. When to wear thermal underwear

The obvious answer to the question of “When should I wear thermal underwear?” is when it’s cold outside. No surprise there.

But some people can handle the cold better than others, so you can decide when to wear thermal underwear depending on your tolerance for cold.

In general, however, thermal underwear is meant for cold weather – for the winter.

That doesn’t mean you shouldn’t wear it at other times of the year because you can, but the majority of people pull out thermal underwear from their dresser drawer when temperatures start to drop and continue to drop.

If you find yourself sweating excessively, or that your skin starts to itch, it may be warm enough outside that you don’t need to wear thermal underwear.

2. Wearing thermal underwear for the active outdoor lifestyle

Many men wear thermal underwear when participating in winter activities such as skiing, jogging, snowboarding, and hiking. A critical factor to keep in mind is that you don’t want to get too warm while exercising.

Your safe bet as an active man is to choose lightweight thermal underwear that wicks moisture, helps keep you dry, and has a comfortable 4-way stretch. And, that you can wear as a base layer under your shorts, skiwear, and pants, or solo.

3. Wearing them around the house

The highest quality thermal underwear – such as those we review above – are built for comfort, and you may find that you enjoy wearing them for lounging around the house.

You may also find that your regular pajamas don’t keep the chill out in the dead of winter, which is a good reason for swapping them out for a pair of thermal underwear.

4. Wearing them for other outdoor activities

If you’ve ever been to an outdoor sporting event, concert, or participate in activities such as camping and fishing in the winter, you understand the importance of staying warm.

Thermal underwear is a must for comfort and warmth during those activities in which you’re more sedentary than active.

5. Choose your fit

We discussed how important it is to get the right fit in our section about thermal underwear buying tips. Fit is crucial to the overall comfort, and it’s up to you to decide what type of fit you prefer – loose-fitting, snug, or something in between.

The fit also depends on the fabric: cotton blends tend to have a looser fit while synthetic and microfibers are more form-fitting.

6. Wear thermal underwear as insulation, not as regular underwear

We’ll talk about base layer vs. thermal underwear in a bit, but the important point is that the design and purpose of thermal underwear is insulation. That said, you shouldn’t wear them as a substitute for regular underwear.

While you can wear thermal underwear for several days without having to launder them, regular underwear (jockeys, briefs, etc.) should be worn for one day and then laundered.

If you wear your thermal underwear in place of regular underwear, you’re going to need to wash them far more often.

7. Wearing socks with long johns

Put your long johns on first, before your socks. Put your socks on so that they go over the bottom of your long john pants.

8. Wearing a thermal underwear top

You can wear a long john shirt as you would a regular t-shirt. Wearing another shirt below your thermal underwear top isn’t advised because it can get a bit uncomfortable.

The different types of thermal underwear

What kind of thermal underwear you choose depends mostly on the type of fabric and weight.

1. Merino wool

We mentioned Merino wool frequently in our reviews of the best thermal underwear for 2020 and with good reason. It’s among the warmest and most comfortable materials used for thermal underwear construction, and it has moisture-wicking properties.

Even better, perhaps, is that Merino wool is environmentally sustainable. After all, once you give Merino sheep a good haircut, their wool will grow back.

2. Synthetic thermal underwear

Synthetic materials are a good choice if you’re looking for a more affordable option for wool thermal underwear. Synthetics include polypropylene and polyester, which don’t absorb moisture (like cotton) and still provide plenty of warmth and insulation.

They’re also useful for wicking moisture from the skin.

Polyester doesn’t quite hold the heat like polypropylene, but it’s easy to care for and wash. It’s also UV-resistant.

3. 100% cotton thermal underwear

It’s hard to beat the comfort of 100% cotton, but it doesn’t insulate quite as effectively as Merino wool. It also doesn’t manage moisture as well as other fabrics.

4. Fabric blends

Thermal underwear often consists of wool/polyester or cotton/polyester blends (or polypropylene) that feature the best of both worlds, i.e., warmth, comfort, insulation, moisture-wicking, and more.

5. The weight of thermal underwear

You can also categorize thermal underwear by their weight, which indicates their thickness.

Lightweight thermals are the thinnest types and often among the most affordable. They’re ideal for intensive activities in cold weather, such as skiing or jogging, and even suitable for regular use in all seasons.

Midweight thermals are multi-functional and warm enough to wear for cold to colder temperatures. But you can also wear them in the fall or spring when temperatures are warmer, but still a bit cool.

Heavyweight thermals are the thickest of all and best for use in the most frigid and blustery conditions.

What’s the difference? Thermal underwear vs. base layer

Things can get a bit confusing when discussing base layers and thermal underwear. Technically, thermal underwear acts as a base layer, i.e., you wear it under your outside layer of clothing, and it’s often worn against the skin.

But an excellent way to stay warm in colder weather is to wear three layers – a base layer, a middle layer (which could be thermal underwear), and an outer layer.

A base layer should prevent you from getting cold, not to keep you warm, if that makes sense. It’s an important point to keep in mind when choosing a base layer.

The ideal base layer should help wick sweat from your body – which many brands and styles of thermal underwear also do. Wet skin will only make you feel colder, and in cases of extreme cold that can be dangerous.

Lightweight base layers garments typically have a looser fit than thermal underwear and promote better air circulation while wicking moisture away from the skin. Heavier base layer materials have more of a snug fit, however.

Silk is a fabric sometimes used in base layer undergarments and has some advantages, such as superior comfort and that they don’t have the added bulk of other garments.

Base layers made from Merino wool are suitable for colder temperatures but also good for most conditions, while synthetic fabrics work well in warmer temps.

In general, however, base layer clothing needs to pull sweat away from the skin as quickly as possible, while also drying fast to keep your skin from becoming too cold.

How we chose the products for our review

There’s more to thermal underwear than meets the eye, which is true of most products. But, for us, choosing the best thermal underwear for 2020 meant studying the factors we used in our buying tips above, namely, fit, comfort, breathability, moisture-wicking, etc.

While the fit is a personal thing, as is comfort, we looked carefully at the fit each type of thermal underwear offered – while using the reviews of customers as an important guide – as well as its overall comfort level.

What did customers think of the fit? How comfortable were they when wearing a particular brand of thermal underwear for their many activities?

A pair of thermal underwear had to be breathable to meet our approval and also able to wick away moisture. A garment that gets wet, cold, and clammy isn’t going to cut it in the dead of winter.

We also evaluated the quality of each product’s seams. Seams affect not only comfort but also durability. The cheaper the seams, the more likely you’ll need to buy a new pair of thermal underwear sooner than later.

Another important factor was the factor. We tried to present a mix of fabric – from polyester to cotton to wool to blends – to provide a comparison.


A good pair of thermal underwear can make the difference between being comfortable during the winter or suffering through it as the temperatures take dive. The right pair will suit your activities and provide a protective layer that keeps you warm and safe.

We’d love to hear your thoughts and observations. Do you have a favorite brand of thermal underwear? Why do you like it? As always, we welcome your feedback.


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