Last updated: 16/10/2022

How we pick our products

27Products analysed

50Hours spent

18Evaluated articles

178User reviews

Thermal underwear is a type of clothing that you wear under your regular clothes to keep yourself warm. It traps the heat in and keeps it close to your body so that you don’t feel cold even when outside temperatures are low. This helps prevent hypothermia, which can be deadly if not treated immediately.

Thermal Underwear: Bestsellers and current offers in the UK

The best thermal underwear in the UK: Our selection

Warmth and comfort this winter with heatwave thermalwear trousers

Looking for a way to keep warm this winter? Look no further than these thermal trousers. Made from a comfortable fabric with a 0.45 tog rating, these trousers will hold more warm air close to the skin and shape to the contours of your body for a perfect fit. Available in white, blue, charcoal and black, these heatwave thermalwear trousers are sure to become your go-to when the temperatures start to drop.

Keep your feet warm all day with these comfortable thermal socks.

Looking for a pair of thermal underwear that will actually keep you warm? Look no further than these heat holders ribbed construction socks. The ribbed construction effortlessly shapes to your body’s natural contours for a better and more secure fit, while the soft brushed inner maximizes the amount of warm air held inside each sock. Plus, the elasticated waistband adjusts to your body for an even better fit. Made from a cotton-rich blend, these socks are sure to keep you cozy all day long. Choose from charcoal or white to match your outfit.

Thermoflux Long Johns: Stay Warm Indoors and Out

Looking for a comfortable and versatile pair of long johns? Look no further than our thermoflux line. Our long johns are available in three different styles, each designed to provide optimal comfort and heat retention. The lightweight (160g/m^2) style is perfect for outdoor winter activities like skiing or running, while the midweight (210g/m^2) and heavyweight (260g/m^2) styles are ideal for indoor wear as home clothes or next-to-skin layers. All of our long johns feature a snug fit that prevents bunching around your waistline or sleeves, as well as four-way stretch fabric that allows for full range of movement. And for added convenience, our long johns have an open fly design that provides quick and easy access when nature calls. So whether you’re looking to stay warm outdoors or simply want some cozy loungewear, thermoflux has you covered.

Thermal Underwear: Frequently asked questions

What types of Thermal Underwear are there and what determines a good product?

There are two main types of thermal underwear. The first is the traditional long johns, which are made from a thicker material and provide more warmth than their shorter counterparts. These can be worn under your clothes or on top as an extra layer for added protection against cold weather conditions. The second type of thermal underwear is called leggings, which have become increasingly popular in recent years due to their versatility and ability to fit comfortably underneath most clothing items without being seen through them (unlike regular long johns). Leggings come with either full-length legs or short ones that stop at the knee area; both options work well depending on what you’re wearing over them.

The main factor is the fabric. It should be breathable and lightweight, but also warm enough to keep you comfortable in cold weather conditions. A good thermal underwear will have a soft feel that makes it easy to wear for extended periods of time without feeling uncomfortable or constricted. Other factors include fit (too tight can make your body overheat), length (longer lengths are better at keeping out drafts) and design features such as zippers, pockets etc..

Who should use a Thermal Underwear?

Anyone who is active outdoors in cold weather should use thermal underwear. This includes hikers, skiers and snowboarders, hunters and fishermen, construction workers or anyone else that spends time outside during the winter months.

Based on what criteria should you buy a Thermal Underwear?

The selection of an appropriate Thermal Underwear is a long-term investment. You should consider the following aspects when buying your new Thermal Underwear:

Make sure you check out the specification of a Thermal Underwear before buying it. There are many factors to consider when making your choice, such as its size and color. You can also get an idea on how people felt about their purchase by reading customer reviews.

What are the advantages and disadvantages of a Thermal Underwear?


Thermal underwear is made of a material that will trap your body heat and keep you warm. It can be worn as an undergarment or on its own, depending on the weather conditions.


The disadvantages of a Thermal Underwear are that it is not as warm and cozy as the other types of thermal underwear. It does not have any insulation, so you will need to wear another layer underneath for warmth. This can be bulky depending on what type of clothing you choose to wear under your Thermal Underwear.

Shopping Guide: Everything you need to know

Which brands and manufacturers are represented in our review?

In our review, we present products from various manufacturers and suppliers. The list includes products from the following brands and manufacturers, among others:

  • Heatwave Thermalwear
  • Heatwave Thermalwear

What is the price range of the featured products?

The cheapest Thermal Underwear in our review costs around 10 pounds and is ideal for customers who are conscious about their money. However, those who are willing to spend more money for better quality can also spend around 36 pounds for one of the more expensive products.