Best base layers for women 2021: stay cosy and comfortable with smart base layers for outdoor adventures
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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 off 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 top and leggings set.
Thermals should hug your body without feeling too restrictive around the waistband, ankles, neck or sleeves.
Some base layers are stretchier than others – we reckoned 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.
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Thermal 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 hoodies for extra warmth. We also look for base layers that use ‘flatlock’ sticking – this avoids any rubbing against your skin.
What material should your thermals be made of?
Many base layers are made with synthetic materials such as polyester, but the best (but often the most expensive) base layers are made with a percentage of merino wool – 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 for when you’re heading into the backcountry without a shower in sight.
Bamboo base layers are more recent arrivals on the market – they’re also a great choice, as they’re soft to wear, antimicrobial and more eco-friendly to produce than synthetic materials.
What do the numbers on thermals mean?
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.
Icebreaker Merino Oasis top and leggings
Base layers are what Icebreaker do best, and they’re always some of the top-performing designs when we test out base layers.
£75 (top), £60 (bottoms)
If you want to invest in a great set of thermal underwear, our pick of the pack are their Oasis base layer top and their Everyday Thermal leggings.
Slip them on and the first thing you’ll notice is how deliciously soft their 100% Merino wool make-up feels against the skin.
The Oasis’ 200g weight is a good warmth to weight ratio for most outdoor adventures, and the Thermal leggings live up to their name, keeping you delightfully warm even on winter hikes and ski adventures.
Icebreaker’s merino layers are worth the spend, and will last you for years without losing their shape or their warming abilities.
The bottoms are available here.
Arc'teryx Motus AR long sleeve top
Base layers are a handy bit of kit to own – but they don’t usually get you many style points. Not so with Arc’teryx’s good-looking Motus.
What we love about this base layer is how little it looks like a base layer – this smart crewneck top looks just as good tucked into jeans as it does with walking trousers.
There’s substance as well as style here, of course – the thermal material is soft against the skin, instantly warming and also great at staying breathable when you pick up the pace.
A boxy cut means this is not the slimmest-fitting or the warmest base layer we tested, but it’s ideal for layering up for autumn adventures.
Runderwear long sleeve top
It’s probably not surprising that our top base layer for runners comes from a running brand, - Runderwear really know how to design pieces that are perfect for keeping keen road and trail runners warm.
This long-sleeved top is stretchy and slim-fitting without being restrictive – it moves so well when you’re jogging that you’ll barely notice you have it on as you clock up the miles.
This is also one of the most breathable base tops in our round-up, great for keeping you warm without overheating on cold weather runs, and even sports built-in mitts you can pop on if your hands get chilly. A short-sleeved version is also launching this autumn.
Jack Wolfskin Arctic XT tights
Get cosy when the mercury drops in a cold weather-specific base layer.
Ideal for skiing, hiking or winter camping (where they also double up as great sleepwear), Jack Wolfskin’s XT tights are super warm and comfy thanks to super soft merino wool, wick away sweat well if you do raise your body temperature and are suitable for wearing in their namesake Arctic conditions.
The only thing to note is that these tights are slightly see-through, so while they make a great base layer for winter sports, they don’t really work as standalone leggings that you could wear to après ski.
Alpkit Koulin Trail long sleeve top
A great base layer top for under £30? You can with Alpkit’s Koulin, a simple, flattering and reliably warm long sleeve top that’s ideal for hiking trips.
We love the bright berry colour and the slim, feminine fit, which is flattering without being too figure-hugging.
The Koulin is breathable if you sweat and also uses Polygiene technology to keep odours at bay – ideal if you’re on a multi-day walk or are camping far away from civilization. There’s even a back pocket for stashing snacks. A bargain!
Acai Winter top and bottoms
£49 (top) £59 (bottoms)
Pleasingly soft and comfortable to wear and with some of the best stretch of all the base layers we tested out, Acai’s warm top and bottoms have clearly been designed with womens’ bodies in mind - they move as you do and hold their shape well after a wash, too.
We like the wide crew neck and longer cut of the top, and the thick, comfy and flattering high waistband of the trousers, which work brilliantly for everything from running to yoga, and are smart enough to wear casually when you aren’t getting active.
CEP Wingtech short sleeve top
We’ve never come across a base layer top designed to improve your posture before, but that’s exactly what CEP reckon their technology does – sensory stripes of material down your shoulder blades help you tell if you’re holding your back and neck correctly.
You may have to wear this figure-hugging top a few times to get used to it, but anything that helps with better running or hiking, especially if you usually wear a heavy backpack, is a great idea in our book.
We also like the longer cut and stretchy material, which keep the top comfortably in place as you move – great for joggers.
Haglofs Actives Wool top and bottoms
Haglofs was founded in Sweden, so it’s not a surprise that they have an eye for cold weather gear.
Their no-nonsense 96% merino Actives range of base layers is designed with snow sports in mind, and the top and long johns are form-fitting and easy to layer, with well-placed flatlock seams that mean you’ll barely feel your thermals even as you ski or snowboard.
The top works as a wardrobe staple, but the leggings do look too much like underwear to stick on for casual use or a yoga class.
The Actives top and bottoms are pricy at £63 each, but we reckon they’re worth it for serious sports lovers, considering they pack a merino wool punch that makes them ideal for long days on and off the pistes.
Paramo Grid Technic long sleeve top
Layering is the key to trapping in warmth when you’re hiking in cold conditions – and Paramo’s Grid top is a brilliant top to add to the mix.
This was one of our favourite base layers on test for all day wear, and it can be worn next to the skin or as a mid layer on top of a thinner thermal top too due to its slightly looser cut.
We like the sweat-wicking grid material, the comfy wider cut, and Grid Technic’s flattering, rather retro looks. Thumb holes are also handy when you’re wearing gloves for winter sports.