Keep it Toasty with the Best Thermal Underwear

We’re constantly being told about the importance of layering for warmth. But you can cut down the bulk by making those layers count. Instead of wearing three pairs of joggers and walking around like you’re hiding stolen goods, you can keep toasty by wearing thermal pants and adding a more appropriate outer layer on top. Hikers, skiers, and other cold-weather adventurers will know how crucial thermal underwear is when it comes to minus temperatures. In our search for the best thermal underwear for men and women, we’ve narrowed it down to nine options to help you beat the cold.

Additionally, we’ve detailed how to choose the right thermal underwear in our buyer’s guide and answered several frequently asked questions.

The best thermal underwear

Top pick: Duofold Men’s Mid-Weight Wicking Thermal Pant

60% cotton, 40% polyester
Moisture-wicking waistband
Pull-on closure
C-vapor technology
Available in four colors

Specification:

Brand: Duofold
Model: KMW2
Weight: 11.4oz

It’s hard to pick a favorite when it comes to thermal underwear. Many products look the same, cost the same, and don’t have any added features to tell them apart. It’s not like you want ten secret pockets and bulletproof kneecaps on your thermal underwear. You want them to fit and to keep you warm. We thought this pair from Duofold was one of the best.

Duofold Men’s Mid-Weight Wicking Thermal Pants are made from synthetic fabrics, a mixture of cotton and polyester, so they wick moisture effectively. This base layer is actually designed for cold temperatures (not extreme cold), and they’re not made for intense activity. However, downhill skiers and hikers would find them suitable unless they’re engaging in their sport at a high level.

See the Duofold Men’s Mid-Weight Wicking Thermal Pant on Amazon

See the Duofold Men’s Mid-Weight Wicking Thermal Pant on Walmart

Best all-polyester option: ColdPruf Men’s Basic Active Wear Crew Pants

100% polyester
No-itch waistband
Dual-layer engineering
Available in two colors

Specification:

Brand: ColdPruf
Model: P2021531
Weight: 1lb

ColdPruf makes a whole range of thermals to cover extreme environments. As you might have guessed from the name, this is their most basic thermal underwear, but that’s not to say it can’t handle the cold. ColdPruf Men’s Basic Active Wear Crew Pants are made from 100% polyester, but they’re dual-layered, which makes them extra toasty. The idea behind the two-layer system is to trap body heat and prevent the cold air from reaching your skin.

We like that they haven’t put any tags or labels on the waistband, which means it doesn’t get itchy or bother your skin. It’s a minor feature, but it adds to the comfort. This long underwear can handle frigid temperatures and is perfect for snow sports.

See the ColdPruf Men’s Basic Active Wear Crew Pants on Amazon

See the ColdPruf Men’s Basic Active Wear Crew Pants on Dick’s Sporting Goods

Best mid-weight layer: Duofold Men’s Midweight Double-Layer Thermal Pant

Inside: 65% cotton, 25% merino wool; Outer: 10% nylon
Pull-on closure
Tagless labeling
Form-fitting
Available in two colors

Specification:

Brand: Duofold
Model: KMO3
Weight: 11.7oz

Duofold Men’s Midweight Double-Layer Thermal Pant employs the same double-layer technology as the Coldpruf pants. However, Duofold has Merino wool in the outer layer. Merino wool is commonly used in high-quality thermals because of its ability to trap warmth in and let moisture out. That extra layer of warmth means these are suitable for some seriously cold environments and would make an excellent hiking and skiing thermal.

Like all Duofold thermal underwear, they have a pull-on closure, tagless label, and flatlock seams that prevent chafing. If you’re still not 100% convinced about this product, check out the 1,000+ Amazon reviews. You’ll find people from all over the world gushing about the quality of Duofold products.

See the Duofold Men’s Midweight Double-Layer Thermal Pant on Amazon

Great for sleeping: Hanes Men’s Red Label X-Temp Thermal Pant

60% cotton 40% polyester
No-rub seams
Shrinkage control
Available in three colors

Specification:

Brand: Hanes
Model: 14520
Weight: 1lb

If you’re looking for a pair of thermals to sleep in, Hanes Men’s Red Label X-Temp Thermal Pants are a great choice. You might have been checking out the products so far, thinking they were a bit heavy-duty for your needs. These thermal pants from Hanes aren’t designed for mountaineering, skiing, or winter exploration. However, they are great if you’re looking for an affordable and comfortable option for sleeping.

The Hanes long johns have a comfortable flat seam that doesn’t rub or cause chafing. They also don’t shrink in the wash, as long as you follow the instructions. There are some reports of the seam ripping after a while, but it should be fine under light use.

See the Hanes Men’s Red Label X-Temp Thermal Pant on Walmart

Best merino wool option: Minus33 Kancamagus Men’s Midweight Bottom

100% merino wool
Interlock seam construction
Odor-resistant
Available in 11 colors

Specification:

Brand: Minus33 Merino Wool
Model: 706
Weight: 1lb

If you’re looking for a seriously high-quality thermal, you should check out the Minus 33 Kancamagus Midweight Bottom. We think this is the best thermal underwear on this list if you’ve got deep pockets. The reason it’s so good is that it’s made from 100% merino wool. We’ve already touched on the benefits of this super-fabric in our buyer’s guide below, but the headlines are that it’s incredibly soft and comfortable, breathable, warm, and lightweight. It’s the perfect material for thermal underwear and other winter gear as it won’t retain odor.

The other benefit of high-quality material like this is that it adapts to the weather. You will be just as comfortable in spring or autumn as you would be in the dead of winter. Sure, they’re considerably more expensive than other pairs of long johns on this list, but they should last a lot longer too. Think of it as a long-term investment in your everyday comfort.

See the Minus33 Kancamagus Men’s Midweight Bottom on Amazon

See the Minus33 Kancamagus Men’s Midweight Bottom on Minus 33

See the Minus33 Kancamagus Men’s Midweight Bottom on Walmart

Comfort first: Fruit of the Loom Waffle Thermal Underwear Bottoms

60% cotton, 40% polyester
Tagless elastic waistband
Moisture-wicking
Available in four colors

Specification:

Brand: Fruit of the Loom
Model: PS10752NB
Weight: 7oz

Fruit of the Loom is a classic clothing brand that makes all sorts of essentials, including casual wear and underwear. Their thermal underwear may not be the best-performing, but you know that it’s going to last. This pair of long johns is pretty standard –- they have a tagless elastic waistband, moisture-wicking ability, and retain your body heat to keep you warm. They are designed for medium-cold weather.

You wouldn’t want to take a pair of these up Mount Everest, but they’ll keep you toasty on a cold winter day.

See the Fruit of the Loom Waffle Thermal Underwear Bottoms on Amazon

See the Fruit of the Loom Waffle Thermal Underwear Bottoms on Walmart

Most versatile men’s set: TSLA Men’s Thermal Underwear Set

95% polyester, 5% elastane
Fleece-lined for extra warmth
Moisture-wicking
22 colorways

Specifications:

Brand: TSLA
Weight: 1.72lbs

With a range of 22 colors and prints, there’s a style for everyone when it comes to the TSLA Men’s Thermal Underwear Set. The polyester and elastane construction allows for extra stretch, a snug fit, and full freedom of movement. The fleece-lined interior provides additional warmth while the polyester is moisture-wicking so you don’t overheat. All in all, this is a great long underwear set with excellent versatility on a budget. For a comparable women’s version, check out the next product on our list.

Some Amazon reviewers noted that they needed to order a full size up for an appropriate fit. Additionally, there is no zipper or fly, so keep that in mind when nature calls!

See the TSLA Men’s Thermal Underwear Set on Amazon

Most versatile women’s set: Thermajane Long Johns Thermal Underwear

92% polyester, 8% spandex
Soft fleece-lined interior
Moisture-wicking and heat-retention
Machine-washable
11 colorways

Specifications:

Brand: Thermajane
Model: J-T-W-1836
Weight: 12.63oz

This budget-friendly set for women comes in 10 colors. While these don’t have many reviews for heavy-duty use, the polyester and spandex construction does offer a four-way stretch.

The interior is fleece-lined for warmth and there are moisture-wicking properties for temperature regulation, making these a great choice for light hikes, comfy days at home, and chilly days outside.

See the Thermajane Long Johns Thermal Underwear on Amazon

See the Thermajane Long Johns Thermal Underwear on Walmart

Tried and true: Smartwool Classic Thermal Merino Base Layer

100% merino wool construction
Excellent temperature regulation
Moisture-wicking and breathable
Excellent for high-impact activities
Odor-resistant

Specifications:

Brand: Smartwool

For many, Smartwool is synonymous with base layers and with merino wool. Smartwool is perfect for layering under outdoor clothing and this moisture-wicking, breathable wool base layer is perfect for winter activities.

The flatlock seams and wool-covered waistband reduce chafing and skin irritation. While on the pricey side, these are undoubtedly one of the best men’s thermal underwear bottoms around.

See the Smartwool Classic Thermal Merino Base Layer on REI

See the Smartwool Classic Thermal Merino Base Layer on Smartwool

See the Smartwool Classic Thermal Merino Base Layer on Moosejaw

Why trust us

We have decades of product testing, snow sports experience, and market research experience on our team. We know what difference the right long underwear can make. The right layers can make the coldest of days much more comfortable and our aim is to make accessing that information as easy as possible.

Who this is for

This guide is for anyone looking for the best thermal underwear, often referred to as long johns or long underwear. We have an array of options with multiple price points and fabric types so you can choose what’s best for your lifestyle and budget.

How we picked

We picked our selection of the best thermal wear for men and women to ensure we had a curated selection that had something for everyone. We wanted variety in price point, fabric, use, sizing, colors, warmth, and durability.

Features to look for in thermal underwear

Material

Most thermal underwear is either made from merino wool or from synthetic fabric, polyester or nylon. Merino wool is considered to be one of the best fabrics for long johns because of its warmth and odor-resistant properties.

Breathability

Breathability is essential, even when it comes to thermal clothing. It refers to the clothing’s ability to let moisture out whilst stopping cold air and water from getting in. If you plan to be exercising, skiing, hiking, or participating in any sort of activity that may result in you working up a sweat while wearing your long johns, you should absolutely be looking for moisture-wicking qualities.

Comfort

Comfort is important with any clothing item. Thermals shouldn’t be so tight that they restrict blood flow or movement, but they shouldn’t let any air in either. You should also look for a pair of thermals that has tagless labeling and anti-chafing technology.

Warmth

Warmth is the primary reason one chooses to buy a set of thermal underwear or base layers. A set of long underwear that doesn’t keep you warm isn’t much good at all. However, a set of long johns to keep you warm at 30° and -30° are two different things entirely. If you want truly warm, soft, and odor-resistant thermal underwear, we highly recommend articles made from merino wool.

Thermal underwear FAQ

Q: Should thermals be tight or loose?

Thermals should be fitted and relatively tight. However, they should not be so tight that they restrict your blood flow or movement. If they are too loose, they will let cold air in.

Q: How do I wash my thermal underwear?

The care requirements for thermal underwear will vary and you should always refer to the manufacturer’s recommendations. Each fabric such as nylon core, merino wool, or recycled polyester will have different care requirements.

Q: Are all thermal underwear odor-resistant?

Not necessarily. While you are bound to sweat in your thermal underwear due to physical exertion and your own body heat, not all models are odor-resistant. Merino wool models are naturally odor-resistant, making them an excellent choice. However, unless treated, synthetic fibers and fabrics are often not odor-resistant. The best thermals for men and women will have odor-resistant properties whether by the nature of the fabric or through treatment.

Q: At what temperature do you need thermal underwear?

You can use them for any temperature you feel cold in. There’s no set temperature for wearing thermal underwear, it’s purely your choice for when you want to stay warm.

Q: What’s the difference between base layers and thermals?

Many folks use these terms interchangeably, but the easiest way to think of it is that thermal underwear is a type of base layer that prioritizes warmth over wicking away moisture, making it great for extremely cold weather. Thermal underwear can be great for outdoor activities but something that wicks moisture is often better because of the temperature regulation that sweat removal offers.