Updated: November 2017

Thermal Underwear Reviews:

When the weather gets cold you want to stay as warm as possible. Thermal underwear have been around a long time. Often called 'long johns', thermal underwear are the perfect under-clothing when you go skiing, ice skating, or just work outdoors during the colder winter months. We set out to research the top selling pairs of long underwear, compare owner reviews along with expert comments, and provide our readers with the latest results. Amazon.com is the best place to find consumer feedback and product reviews for thermal underwear. We got lots of information on brands like Hanes, Duofold, Carhartt, Calvin Klein, and Indera. What sizes fit best? Do you need wicking material? Should you buy one piece or two piece designs? Most of the sales in this category are for men, so we will focus our writing on that. The one big factor that goes into selecting a solid pair of thermal underwear for guys is - Will it keep you warm, but not too hot? See our findings and buying guide below.

Choosing a Thermal Underwear - What fabric/material will be right for you? Cotton, cotton-polyester blend, flannel, polyester, wool, wool blends. Most positive comments were for underwear made with a cotton/polyester blend. The cotton kept them warm while the polyester layer was able to wick moisture away from the skin. It really comes down to what type of activity are you going to be doing while wearing the thermal underwear. Do you bike to work on cold days? Are you in the construction field doing hard labor outdoors all year long? Maybe you just want to add that extra layer of warmth while hanging around your house. There are tops, bottoms, and one piece thermal underwear called union suits. Hanes and Carhartt have the most popular union suits - the Carhartt one is made with 100% cotton rib knit fabric. while the Hanes is a blend of cotton and polyester. The Duofold Men's Mid Weight Wicking Bottom are a top seller and made with a 60% cotton/40% polyester blend. Sizing goes from small up to XX large. They come in navy, black, and winter white. The bottoms are meant for cold weather, low impact activities. Features include a wicking waistband, moisture control, and flatlock seams to avoid irritation. Check the sizing chart on any brand. Many comments posted online refer to things like 'long in the crotch' or 'went with a size smaller'. The good news is that Amazon has great customer service and excellent return policies so you can easily get the thermal underwear that fits. When it comes to tops, the Carhartt Base Force Super-Cold Weather crew neck top and the Duofold mid weigth wicking crew neck top are great choices. There are sets of tops and bottoms available, like the Men's Thermal Underwear Set Top & Bottom Fleece Lined from C3 Fashion Express. What are you going to pay for thermal underwear? We found bottoms top out at $40 and the tops $35. The one piece union suits go up to $70. The most common complaints amongst all the brands was sizing and fit. Several people said that the pants just don't fit properly. They are too loose in the crotch and the butt area. If you are going to wear underwear, you want it to fit snug, but not too tight. You can browse the best selling thermal underwear here.

Best Thermal Underwear:

RECOMMENDED - After plenty of research, the Duofold Men's Mid Weight Wicking Bottom came out on top for 'best bottoms'. Yes, sizing is still an issue for some. Most of the time going a size smaller is the best choice - fits snugger. With the 60/40 blend of cotton and polyester you are assured of staying warm but not sweating to death. The Carhartt Men's Heavyweight Cotton Thermal Bottom has more sizing options than Duofold, but they are made with 100% cotton. Carhartt thermals are a bit more expensive than the competition, but owners say they are worth it. Again, consider going a size smaller than usual for the best fit. Great for wearing under camo bibs while hunting, jeans when doing outdoor construction, or regular clothing. Warm and durable are two words we saw most often in owner reviews posted on Amazon. Double elastic waist, reinforced seams for durability, and rib knit leg are just a few of the features that set these apart from the others. A matching top is available for $50.

Union Suits:

RECOMMENDED - Want a full length set of thermals, consider the Carhartt Men's Midweight Cotton Union Suit for under $50. You may feel like Santa Claus in these thermals or some guy from the 1850's, but they are warm and comfortable. The Carhartt's are made with premium 8 ounce fabric and the midweight cotton union suit gives you total body warmth. If you are looking for convenience, then the fly and back opening with button closures should peak your interest. While some owners say the 1 button butt flap could be designed better, most are totally happy with the comfort and durability of these. The Duofold is a bit different - it features a 100% cotton inside layer with a 65% cotton/25% merino wool/10% nylon outer layer. Does that make a difference? You bet, those that live in really cold weather climates (like Chicago in the winter) say the Duofold is a better option than the Carhartt. The two-layer thermals are meant for guys who are outside working in the coldest climates. While the Carhartts are great for 30 to 50 degree temps, the Duofold can go even lower.