14 best base layers for men and women, tried and tested

Thermals, long johns, base layers – whatever you want to call them, there’s nothing like a warm layer worn next to the skin to help keep the chill of colder weather at bay.

Whether you’re skiing, hiking or cold-weather camping, layering up is the best way to trap in heat and keep cosy in the great outdoors, and a good layering system starts next to the skin with a quality base layer set of top and leggings.

The best base layers should hug your body, without feeling too restrictive around the waistband, ankles, neck or sleeves. Some base layers are stretchier than others – we found thermals with some stretch offered more warmth on test, as there’s no empty space between the fabric and your skin for the cold to creep in. Base layer tops usually have a crew neck or a high, zipped neck – the latter can double up as a neck warmer, and some tops also sport hoods, for extra warmth. Look for base layers that use ‘flatlock’ sticking, to avoid any rubbing against your skin.

Many base layers are made with synthetic materials, such as polyester, but the best base layers are made with a percentage of merino wool (though, they will be pricier). Merino is very warm but still highly breathable and is great at wicking away sweat. It also has naturally antimicrobial properties, making it perfect if you’re getting active or heading into the backcountry without a shower in sight. Even better, try alpaca wool – it performs just as well and tends to be produced more sustainably.

Bamboo base layers are more recent arrivals on the market – they’re also great options, as they’re soft to wear, antimicrobial and more eco-friendly to produce than synthetic materials. You may see base layers listed with a number, such as 140 or 220 – this refers to their weight in grams, and the higher the number, the warmer, but heavier, the base layer.

How we tested

We tried out each of these base layer sets during autumn hiking and camping trips, wearing the base layers alone and under waterproofs and testing for warmth, comfort and breathability. We were looking for base layers that added instant warmth, felt comfortable under other layers and were breathable on the go. Base layer no-nos? Feeling itchy or restrictive, not wicking away sweat and not feeling soft and flexible against the skin.

Why you can trust us

Sian Lewis is an award-winning travel and outdoors journalist and has written for IndyBest since 2020. Adept when it comes to assessing outdoor gear, Sian has previously brought readers her verdict on the best camping gear, hiking gear, and winter sports equipment on the market, including the best snow boots, thermal socks and ski gloves.

The best base layers for 2024 are: