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Buying guide for best men’s thermal underwear bottoms

When you spend time outdoors in cold weather, wearing layers is the best defense against the chill. Men’s thermal underwear bottoms make the perfect base layer to wear under pants when you want to stay as warm as possible in cold weather.

Also known as long underwear or long johns, these garments are designed to be the first layer next to your skin. They offer a snug fit, so you can wear them under most pants, including those meant for skiing and snowboarding. Thermal underwear bottoms can help your body maintain its natural heat without getting sweaty and uncomfortable. And you can find versions suitable for mild winters or more extreme temperatures.

To find the best men’s thermal underwear for your needs, you should first consider how you plan to wear it, what style you need, what materials are best for keeping you warm, and how the garment should fit for maximum warmth. You also want to think about the weight, breathability, and moisture-wicking properties of the fabric.

men's thermal underwear bottoms
Synthetic thermal underwear bottoms are usually the most durable and can provide years of wear, which makes them a great value.

How to buy the best men’s thermal underwear bottoms


Before buying thermal underwear, it’s essential to consider how you plan to use it. If you’re looking for an extra layer to wear under your pants outside on cold days, most pairs of men’s thermal underwear bottoms can work well.

However, if you plan to go skiing, snowboarding, hiking, or engage in some other outdoor activity that will keep you out in the cold for long periods, you need to be more selective. The thermal underwear bottoms should provide warmth as well as offer enough stretch to allow you to move freely when heading down the slopes or climbing up a hill.


Men’s thermal underwear is available in two styles: a one-piece garment, once referred to as a union suit, or two separate pieces, one for the top and one for the bottom.

Separate thermal underwear tops and bottoms are generally the most versatile and easiest to wear. You can wear just the bottoms on days when your coat or jacket provides enough warmth for your upper body but you need an extra layer for your lower body. You can wear the two pieces together on very cold days to make sure your entire body is warm enough for the weather.

It’s also much easier to go to the bathroom while wearing a separate thermal top and bottom. With a one-piece garment, you have to remove all the layers on top to take the long johns down to use the bathroom. The separate pieces also allow you to remove layers as needed so you don’t get too warm.

Materials to consider

Men’s thermal underwear bottoms are available in several different materials that are very soft and help regulate your body temperature. The most common include the following:

Synthetic fabrics: Polyester, nylon, spandex, Lycra, and other synthetics are highly durable and offer good stretch for these garments. They’re effective at wicking away moisture and work well in extreme cold. Some synthetic fabrics are combined with natural fibers for greater heat retention and moisture-wicking properties.

Wool: These thermal underwear bottoms are usually made of merino wool, which effectively regulates body temperature. They’re breathable and have a lightweight feel. Woolen long johns can also help keep you warm even when they’re wet.

Cotton: These thermal underwear bottoms are more affordable than other options, but cotton absorbs moisture from sweat, so these garments can leave you feeling cold and wet. They’re not a good option for activities like skiing, snowboarding, and hiking, but they can be effective for everyday wear in cool weather.

Silk: These lightweight garments can help you stay warm in moderately cold weather. They’re extremely soft and smooth, but they aren't as effective at wicking away moisture as wool or synthetic long johns.

How should thermal underwear bottoms fit?

Men’s thermal underwear should fit snugly without being too tight. They should almost feel like a second skin to provide proper insulation between your clothing and body. A snug fit helps trap body heat, so you’re able to maintain your body temperature even when outdoors in cold weather.

Silk thermal underwear bottoms tend to absorb odors, so they usually have to be washed each time they’re worn.


Features to look for in men’s thermal underwear bottoms

Fabric weight

Men’s long underwear is available in multiple weights, so you can wear different garments in different temperatures. You want to choose the fabric weight based on the weather conditions you plan to be in and your activity. The most common fabric weights for thermal underwear include the following:

Ultralightweight: These extremely lightweight thermal underwear bottoms are suitable for mild to cool temperatures.

Lightweight: These work well in cool to moderately cold temperatures and are ideal to wear during exercise.

Midweight: These garments are appropriate for moderately cold to cold temperatures. They’re typically the most versatile option and work well for most activities.

Heavyweight: These thermal underwear bottoms are meant for extremely cold temperatures and strenuous activity in the snow.

Fabric qualities

Moisture-wicking: It’s essential that your thermal underwear bottoms wick moisture away from the skin so you stay dry and warm no matter the weather conditions. Most materials lose their ability to trap heat when they’re wet, so you’ll get cold more quickly if your long johns are wet.

In addition to wicking away moisture like rain and snow, you want your thermal underwear to effectively wick away your sweat when you’re active outdoors or you run the risk of lowering your body temperature and developing hypothermia.

Breathability: To avoid sweating in the first place, it helps to choose thermal underwear made of breathable material. The fabric allows air to pass through more easily, which in turn helps you maintain your body temperature to prevent overheating. Your thermal underwear should keep you warm without causing you to overheat.


While the color of your thermal underwear bottoms doesn’t affect their performance, most people prefer to have clothing in shades they like. These garments are available in a wide array of colors, including neutrals like black, white, and gray, as well as bolder colors like blue, red, and green. It’s entirely a matter of personal preference, so choose your favorite color.

men's thermal underwear bottoms
Cotton thermal underwear only works for those occasions when you’re outside in cold temperatures but relatively inactive, such as watching a football game. That’s because cotton doesn’t wick moisture away from the skin, so the garments don’t perform well if you sweat.

How do I accessorize men’s thermal underwear bottoms?

Thermal underwear top

While your thermal underwear bottoms keep your lower body warm, you need a thermal underwear top to keep your upper body comfortable. The two pieces are usually sold separately, but most brands offer coordinating tops and bottoms to make it easier to choose the right pieces.

Down jacket

If you’re going to be out in extreme temperatures, pair your thermal underwear with a men’s down jacket. These jackets are very lightweight and highly insulated to help trap body heat so you stay as warm as possible.

How much do men’s thermal underwear bottoms cost?


The most affordable men’s thermal underwear bottoms typically cost between $6 and $19. These long johns are usually made of cotton or synthetic blends and are ultralightweight or lightweight, so they aren’t the best option for extreme cold.


These men’s thermal underwear bottoms usually cost between $20 and $70. They’re typically midweight and made of a synthetic blend, wool, or silk, so they can work well for a wide range of conditions.


The most expensive men’s thermal underwear bottoms typically cost between $70 and $140. They’re usually made of a synthetic blend, wool, or silk and are heavyweight, so they work well in extreme cold and snow.

If you want wool thermal underwear but wool irritates your skin, look for thermal underwear bottoms made of merino wool. It’s less likely to cause itching than other types of wool.



  • Avoid thermal underwear that’s too loose. Loose garments create air pockets, so they can’t effectively trap your body heat. Instead, your thermal underwear should fit right against your skin without being so tight that it restricts movement.
  • Wear bacteria-resistant thermal underwear for camping or hunting. If you won’t have a chance to shower for a few days, the fabric can help absorb odors to keep you smelling fresh.
  • Tuck your thermal underwear bottoms into your socks. That ensures that there aren’t any gaps where your skin is exposed and cold can get in.
  • Choose fabric weight according to activity. If you’re hiking at a leisurely pace, you’ll want heavyweight underwear to keep you warm. If you’re cross-country skiing, you’ll want lightweight or midweight underwear to avoid overheating.
men's thermal underwear bottoms
The seams on thermal underwear bottoms can irritate the skin if they’re not cut properly. Look for garments with sealed seams to avoid any chafing.


Q. Should I wear regular underwear beneath men’s thermal underwear bottoms?

A. You can wear underwear under your thermal garments, but it isn’t necessary. If you wear boxers or other loose-fitting underwear, it can bunch up under the long johns and become uncomfortable. However, wearing regular underwear beneath your thermal underwear can extend the time you can wear it without having to wash it.

Q. Do thermal underwear bottoms work as a base layer?

A. They serve as an excellent base layer in winter. They help insulate the body to trap heat and keep you warm, but they also wick moisture away from the skin to keep you dry. That allows you to maintain your body temperature, so you can stay warm even in frigid temperatures.

Q. How do I clean thermal underwear bottoms?

A. that depends on the material. Some thermal underwear bottoms, such as those made of wool or silk, require hand-washing, but those made of cotton or synthetic blends can be machine washed. Always check the care label to determine the proper way to clean your thermal underwear.


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