Is A Base Layer The Same As Thermals?

Want the right underclothes to stay warm, but aren’t sure where to start? You’re in the right place!

Thermals can be viewed as a type of base layer. However, both thermals and other base layers come in a variety of materials that may have an effect on how and when you wear them. Some focus more on heat retention, while others focus on keeping sweat at bay.

Neither thermals nor base layers can be classified as just one thing. There is a wide array of options out there to choose from. Different styles and materials can give you different results. Read on and you’ll learn the differences and similarities between thermals and base layers as well as what different base layer materials can do for you.

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Why Thermals And Base Layers Are The Same Thing … Yet Different

Thermals and base layers can be looked at in a variety of ways. That said, most campers just want to know what will be comfortable and help to keep them protected from the chill of cold temperatures. Unless we’re getting highly technical with our definitions, thermals and base layers are basically the same thing.

An easy way to look at it is that thermals are a type of base layer. Often, thermals are base layer options that place a higher focus on warmth rather than wicking away sweat. Consequently, many choose thermals when they are more focused on fighting the cold than fighting sweat.

In situations where you know you may also be sweating a great deal, for example, while hiking, backpacking, or even setting up a campsite, you’ll want to aim for different kinds of base layers. Those that focus on wicking away sweat can help to keep you more comfortable in more physically intense scenarios

Have you ever worked up a sweat and then felt cold right after? As many know, sweating is the body’s way of cooling us down. However, once we’ve cooled down the sweat on our skin can leave us colder than we might like. If you also happen to be out in cold weather, that excess cold can also become somewhat dangerous.

To answer that problem, sweat-wicking base layers push the sweat away from your body to keep your body temperature from sinking too much.

In summary: your base layer can be more focused either on insulation or on wicking away sweat. Generally, thermals are a type of base layer more focused on insulation.

What Temperature Do You Need Thermals?

This is a harder question to answer than you’d think because of how many different types of base layers and thermals there are.

You should wear thermals if you are going to be outside below 50 degrees Fahrenheit for more than half an hour doing low-intensity activities.

I can only answer for myself, personally, when it comes down to it because we’re all different.

But, personally, I would only wear thermals if it’s going to be a max high of around 50-60 degrees Fahrenheit. Any hotter than that and it gets uncomfortable for me. And I will only wear them if I’m going to spend more than 30 minutes outside doing low-activity behavior (sitting around a campfire for example).

If I’m exercising or doing a sport, I might choose a more lightweight base layer that won’t get so hot.

Do Thermals Go Under Clothes?

Thermals are ideal for cold weather. They are made to provide a layer that keeps your body heat trapped. Because of that, it is ideal to wear them as close to your skin as possible. Much like base layers, thermals should basically act as a second layer of skin.

If you’ve ever heard of “long johns” or long underwear, you probably have at least a basic image of what thermals might look like. These days, thermals have evolved quite a bit, resulting in different types of thermal clothing, from the well-known adult onesie to turtlenecks, as well as socks and 2-piece outfits. That way, you can make the selection that makes the most sense for you.

Many people wear thermals between their underwear and their outer clothing. In most cases, adding a whole extra layer of clothing under your outfit would be too much. However, if you’re going to be out in the cold for anything from camping to a fun day out sledding or skiing, they can be the difference between a miserable day outside or an awesome day.

I know for me personally, I’ll admit that I wear underwear under my thermals. I feel like I can wear them longer if I can switch out my underwear without having to wash my thermals. Maybe that’s gross to someone else–but there you have it.

When it comes to sweat, we all have different experiences. Each body is built in a unique way, and some of us sweat more easily than others. At the core, base layers and thermals are about keeping each body comfortable.

Heavier campers may have different needs for camping in general when compared to others, especially when it comes to base layers and other clothing. If you’re a heavier type, make sure to check out our article for tips to make camping a fun and memorable time here.

Are Base Layers Meant To Keep You Warm?

Ultimately whatever the design, a base layer is meant to keep you warm.

It can be argued that a base layer can help you sweat more efficiently, but that’s controversial and a whole separate topic. I talk a little bit about it here.

The part worth noting is how certain materials work to keep you warm. Some focus more on trapping your body heat while others wick away moisture to keep you from experiencing too much of a cooldown when you’re sweating. By having an understanding of what the various base layer materials do, you’ll be able to select the right base layers for any given situation.

Base layers aren’t just for daytime. In fact, they are often needed at night by those who like to camp in colder weather. That said, the combination of base layers and a warm sleeping bag can be a tricky one. How do you stay warm without ending up in a puddle of sweat? Our article on the topic here can help guide you through a peaceful (and sweat-free) night’s sleep.

Types Of Materials Used For Thermals And Base Layers

There’s a lot more to understand about base layers and thermals beyond the differences and similarities between them.

Both can include different types of materials, and it’s important to have an understanding of what each material is good for. Some base layer materials might be great for lounging around camp, but awful for backpacking or cold weather camping.

Below, you’ll find a brief list of the different kinds of materials used in base layers and what advantages and disadvantages come with them.


Synthetics are one of the most popular options you’re likely to find out there. They include materials like nylon and polyester. Each unique blend you find can offer slightly different features, with some being more effective in certain aspects than others.

Generally, synthetics are considered to be good options for wicking away sweat. However, you will want to be careful to make sure they don’t get too wet, as they may lose some heat retention and begin to stink. That said, they are made to fit comfortably, dry quickly, and are often quite affordable.

This is the type of thermals that I have from Coldpruf (got them on Amazon several years ago and still love them). They are made for very cold weather and they do help a lot. I was able to sleep in 33 degree weather with a couple more layers and just a sleeping bag without an issue.

My thermals do stink after some use (like a couple days). Not as fast as some other materials, but it’s still worth noting.


There’s no denying that cotton is comfortable. That’s why it’s often such a popular choice for regular clothing as well as underwear. However, it may not be the best material to use as a base layer if you’re out camping.

Cotton is breathable, making it a nice, light material if you’re just hanging out in warm weather. As nice as it is in those situations, it doesn’t absorb sweat or water well and can easily become very cold if it gets too wet. On top of that, cotton doesn’t dry as quickly as synthetics. Overall, cotton is a great choice if you’re hanging out in a warm, dry place but not for sweat or wet weather.

I should mention that cotton can even work fine for cold weather if it’s dry and you are dry. If you’re sweating a lot then you should really consider other materials.

Because cotton is typically such a reliable material, many campers argue that it may actually work well as a base layer. If you want to learn more about whether cotton is the ideal base layer choice or not, take a look at our article on the matter here.


You may be surprised to find silk listed as a decent base layer option. What’s worth keeping in mind is that the material can only handle so much. It does offer a basic ability to wick sweat and fits very comfortably under your other clothes.

That said, it’s not an ideal choice if you’re doing anything highly physical. If you’re just hanging out at camp or maybe going for a short walk then silk is perfectly viable. However, for cold weather, hiking or backpacking, you’ll want to go with something that is a little better for absorbing wetness.

Silk also is known to stink pretty quickly.


Though it may be surprising to some, wool is actually one of the best options out there that you can use as a base layer. When many people think of wool, they tend to think of clothing that is itchy and overly-warm. However, the merino wool often used in base layers is actually quite soft and comfortable.

On top of that, it offers the ability to help regulate your body temperature rather than just heating it up. Although the sweat-wicking abilities may not be quite as good as many synthetics, wool is fantastic for repelling odors. As a result, it’s a great option when you know you won’t have the chance to shower for a while.


Peter is a software developer who loves to take every opportunity to go outside that he can get. Peter grew up going on long backpacking excursions with his family every Summer and now enjoys staying at the beautiful Texas State Parks and swimming in the amazing Texas Rivers.

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