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When temperatures drop, it’s time to layer up. To cut down on excessive and bulky layering, start with a base layer of warm long johns. 

Also known as thermal or long underwear, long johns are two-piece garments — a top and a bottom — that you can wear together or separately, based on your needs. While all long johns have long sleeves and legs, their material and weight vary, and determine how warm and toasty they keep you. 

In this article: Meriwool Men’s Base Layer Merino Wool Heavyweight Thermal Pants, Hocosa of Switzerland Women’s Long Underwear Pants and Merino Wool Base Layer Women’s Thermal Shirt.

How do long johns keep you warm? 

Long johns are made of closely knit synthetic or natural fibers that retain heat. Because layering can make you sweat, especially if you’re going between outdoors and indoors, you want a pair that also offers breathability so you don’t overheat.  

How do you wear long johns? 

Long johns are made of thin fabric so you can comfortably wear them underneath pants and long-sleeved shirts. You can wear underwear and bras underneath them, as they aren’t meant to replace undergarments. You can also wear a tank top beneath a thermal top for extra warmth. The tops wear well under flannel shirts and wool sweaters and can provide a buffer from itchy outerwear. 

If you’re skiing, hiking, hunting or camping in the winter, long-john bottoms are great under snow pants. For outdoor winter activities, choose long johns with an “athletic” or tighter fit, as well as moisture-wicking properties to reduce your risk of hypothermia as you sweat.

Long john materials

Thermal underwear is made from a variety of materials: 

  • Cotton is a natural, breathable fiber. Cotton long johns are good for lounging around the house, sleeping and layering in mildly cold weather. They don’t retain much heat. Cotton does hold onto moisture, though, so don’t wear cotton thermals for outdoor winter activities where you’ll be sweating. 
  • Merino wool is derived from sheep and is naturally insulating. It’s also odor-resistant, moisture-wicking and breathable so you won’t overheat. Merino wool long johns are expensive, but you can find affordable pairs that blend merino wool with less expensive materials. 
  • Silk naturally holds in your heat while wicking away moisture. Another advantage of silk long underwear is its featherlight weight; you’ll barely notice it’s there underneath your clothing. The downside is that silk thermals are expensive, not that durable and retain odor.  
  • Synthetic thermals are often made of polyester. There are also synthetic blends of nylon, rayon, polypropylene and spandex. These materials are durable, wick sweat well and often are treated with a finish that inhibits odor. 

Long john weights 

There are four common weights for long underwear:

  • Feather, ultra-lightweight or microweight is suitable for mild winter weather.
  • Lightweight is suitable for moderate to cool temperatures. 
  • Midweight is suitable for cold weather. 
  • Heavyweight is best for frigid and freezing winter conditions. 

Best men’s long johns

Best Smartwool Mens Merino 250 Baselayer Bottom

Smartwool Men’s Merino 250 Baselayer Bottom 

These high-end merino wool bottoms keep out the cold and are user-recommended for winter camping and backpacking. They wick away sweat and don’t cause chafing. The interlocking natural fibers offer thermoregulation and breathability.

Sold by Dick’s Sporting Goods

Best Meriwool Mens Base Layer Merino Wool Heavyweight Thermal Pants

Meriwool Men’s Base Layer Merino Wool Heavyweight Thermal Pants

These heavyweight thermals have been worn by satisfied users in the Arctic Circle to keep them warm in subzero conditions. The 400-gram-per-square-meter merino wool blocks cold drafts while also letting your skin breathe.

Sold by Amazon

Best Merino Base Layer Merino Base Layer

These midweight merino wool bottoms come with wool socks so that your lower half is covered. These long johns are versatile for indoor and outdoor use. They’re also available in light and heavy weights and are machine-washable.

Sold by Amazon

Best women’s long johns

Best Hocosa of Switzerland Womens Long Underwear Pants

Hocosa of Switzerland Women’s Long Underwear Pants

With a lightweight blend of merino wool and silk, these bottoms feel luxurious on the skin and keep you just as warm as bulkier long johns. They wick away moisture and you can get away with not washing them for weeks.

Sold by Amazon

Best Merino Wool Base Layer Womens Thermal Shirt Merino Wool Base Layer Women’s Thermal Shirt

This midweight merino wool top comes with a pair of wool socks. The top is soft and available in 37 colors. It’s perfect to wear under a sweater or cardigan, but pretty enough to wear alone.

Sold by Amazon

Best men’s long johns for the money

Best Fruit of the Loom Mens Classic Midweight Waffle Thermal Henley Top

Fruit of the Loom Men’s Classic Midweight Waffle Thermal Henley Top 

This classic thermal top can be worn standalone or under your favorite flannel for milder days. The cotton-polyester blend fits close to the body and whisks moisture. It’s a good value and the waffle weave is attractive.

Sold by Amazon

Best TSLA Mens Thermal Underwear Set

TSLA Men’s Thermal Underwear Set 

This affordable microfiber top and bottom are warm, soft and moisture-wicking. They keep you warm when the temperature drops below freezing and can be worn for sports. Be aware that they run small, so you might want to size up.

Sold by Amazon

Best women’s long johns for the money

Best Thermajane Long Johns

Thermajane Long Johns

This fleece-lined base layer can be worn as pajamas or under clothing outside in freezing weather. The fuzzy lining makes this set thick, but not too bulky. The material has some stretch, which makes the bottoms as comfy as leggings.

Sold by Amazon

Best Fruit of the Loom Womens Micro Waffle Thermal Set

Fruit of the Loom Women’s Micro Waffle Thermal Set

With the softness of cotton, these cotton-polyester long johns trap heat due to their synthetic fibers. The top and bottom work great as pajamas and the leopard print is fun for sleeping. The waffle weave is a winter classic look to wear on top and out of the house.

Sold by Amazon

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