Base layers are essential for experiencing the outdoors in the colder months. Perfect for mountain adventures in particular – if you combine your base layer effectively with a good mid layer and a protective shell jacket, you’ll be adventuring all day long.
Related: Best Hiking Fleeces for Women
But base layers aren’t just for summiting snowy peaks. They can be a fantastic way to regulate body temperatures on a chilly morning run, or provide a layer of insulation against chilly winter winds. As the nights draw in and there’s a nip in the air once again, we’ve tested out the best base layers and selected our favourites, ready for your winter adventures.
Páramo’s Grid Technic base layer stole the top spot this year thanks to its excellent temperature regulation and all-around versatility in the outdoors. We also liked the ‘women-specific’ shape that contours a curved physique nicely. It’s fully recyclable too thanks to the Páramo recycling scheme. Not bad, not bad at all.
Bamboo Clothing’s Sudbrook base layer, on the other hand, came in at a close second thanks to its sleek design, neat design features, and decent temperature regulation during our tests. Due to the cotton content, it wasn’t quite as good at temperature regulation as the Grid Technic’s polyester build. That being said, we still think it’s got a lot to offer in terms of warmth.
The Best Base Layers for 2025 – Tested and Reviewed
From glacial walking and ice climbing right through to daily dog walks in the middle of winter, here’s our favourite base layers for a whole range of outdoor activities. Tried and reviewed by our expert team of women’s gear testers, keep your eyes peeled for updates as we continue our testing throughout the year.
- Páramo Women’s Grid Technic – Best Women’s Base Layer Overall
- Bamboo Clothing Sudbrook Slim Fit – Our runner-up
- Howies Long-Sleeved Merino Base Layer – Best Merino Wool Base Layer
- Megmeister Drynamo Long Sleeve – Best Technical Base Layer
- Helly Hansen LIFA Merino Midweight Pants
- Artilect Boulder Crew 125
- Megmeister Drynamo Winter Turtleneck
- Patagonia Capilene Thermal Weight Bottoms
- Smartwool All-Season Merino Crew
- Mammut Aconcagua ML Tights
Editor’s Note: This article was updated in October 2025 to ensure that all of the products are still available for purchase.
1. Páramo Women’s Grid Technic
Best Women’s Base Layer Overall
Price: £85
Weight: 200g
Material: Parameta® G fabric
Páramo have done it again and surpassed all expectations. At first glance this looks like a mid layer, and I was concerned that it would be heavy and uncomfortable against bare skin. But at just 200g, it’s not heavy in the slightest, and I was surprised to find that even when wearing this without a layer underneath, it regulated body temperatures perfectly. The Grid Technic keeps you cool when undertaking a steep, uphill climb, but warm at altitude. It’s roomy enough that it could also double up as a mid layer with an extra base layer underneath, saving all-important space and weight in your pack.
Related: Best Walking Boots for Women
Plenty of ventilation meant that sweat escaped easily, so the Páramo Grid Technic never felt damp. The zipped neck saved the need for a buff, and I loved the little design features too, such as thumb loops to stop an exposed strip of skin between gloves and your base layer.
It’s described as a three-season base layer, but if layered and used as a mid layer, I’d say it’s a must for winter Alpine activities too.
Full Specifications
Fair Trade / fully recyclable through Páramo / variable ventilation / thumb loops / both insulation and wicking properties / zipped neck.
Buy The Páramo Grid Technic: £85 at Paramo-clothing.com
2. Bamboo Clothing Sudbrook Slim Fit
Our runner-up
Price: £39
Weight: 200g
Material: 68% Bamboo Viscose, 28% Organic Cotton, 4% Elastane
Sometimes simplicity is best, and that’s certainly the case with the Bamboo Clothing (BAM) Sudbrook base layer. The slim fit means that it traps air against your body, and I was really impressed with the temperature regulation, which meant that it performed just as well on a hilly bike ride as in the cool mountain air. It’s a sleek design that will go with any of the rest of your gear, with good design features such as thumb loops.
BAM is known for producing ethically made clothing, made largely from bamboo, at affordable prices. The only downside for me was that it wasn’t the quickest to dry and isn’t fully moisture-wicking. The cotton content meant that the fabric retained moisture a little.
Full Specifications
Moisture-wicking / thumb loops / 200gsm single jersey / naturally hypoallergenic / form fitting / versatile / environmentally friendly.
Buy The BAM Sudbrook: £39 at Bambooclothing.com
3. Howies Women’s Light Merino Base Layer
Best Merino Wool Base Layer
Price: £65
Weight: 180g
Material: Merino wool
In terms of value for money, Howies’ long-sleeved merino base layer is unbeatable. Being 100% Merino wool, it was really snug, and the warmth-to-weight ratio is pretty astonishing. As the day heated up, I did find that this wasn’t the best base layer at regulating body temperature though, as I did start to sweat a lot. It wasn’t the quickest to dry either, but because it’s Merino wool, it had the bonus that I could wear it for multiple days on the trot without it starting to smell.
I particularly recommend this base layer for prolonged periods of time in cold conditions (for example, a multi-day trek), when you’re going to need that extra bit of warmth, though it wouldn’t perform so well on a cycle or trail run. In terms of comfort, I found it absolutely superb and really soft against skin.
Full Specifications
Odour-resistant / moisture-wicking / highly breathable / lightweight / naturally antibacterial / flat locked seams / body temperature regulation / slim fit.
Buy The Howies Women’s Light Merino Base Layer: £65 at Howies.co.uk
4. Megmeister Drynamo Long Sleeve
Best Technical Base Layer for Women
Price: £40
Weight: TBC
Material: 44% polypropylene Dryarn, 44% nylon 6.6, 12% elastane
Everything about the Megmeister Women’s Drynamo long sleeve base layer screams technical and I could tell that it has been designed with extreme physical exertion in mind. This base layer was jam-packed with design features. The ventilation is nothing short of amazing. Back, armpits, chest, under the chest, anywhere that could possibly sweat has plenty of ventilation to let the moisture out.
This would be a particularly great choice for strenuous sport in cold weather, for example trail running in the midst of winter. It’s also a fantastic choice for cyclists. The back of this top is lower than the front, meaning that even if you’re hunched over handlebars, you’re not going to risk exposing skin to the elements. The only downside for me was that there was so much ventilation that in windy conditions, it let a fair amount of air in.
Full Specifications
Body mapping ventilation / 4 way stretch / moisture-wicking / ventilating air pockets / thermal insulation / no seams / antibacterial and anti odour functions.
Buy The Megmeister Drynamo Long Sleeve: £40 at Shop.megmeister.com
5. Helly Hansen LIFA Merino Midweight Pants
Price: £85
Weight: 190g
Material: Merino wool, polypropylene
Featuring a 2-layer construction of 100% merino wool on the exterior and highly breathable LIFA fibres on the interior – these LIFA pants from Helly Hansen are very impressive. LIFA, in case you didn’t know, is HH’s own polypropylene composition that’s both hydrophobic and moisture-wicking.
During my tests, I found that these base layer pants worked particularly well for hiking during the winter months, as well as skiing. I also found them to be very comfy against my skin which worked nicely for recharging at the campsite.
While there’s loads of fun graphics and designs to choose from, there’s also more discrete colour options available too. Other notable features include: flat lock seams for optimal protection against the elements, and an elasticated waistband that – crucially – doesn’t lose its shape and elasticity over time.
Full Specifications
XS to XL / 2-layer construction / 100% merino wool exterior / LIFA fibre interior / flat lock seams / non-itch fabric / elastic waist / multiple pattern and colour options / non-merino version available.
Buy The Helly Hansen LIFA Merino Midweight Pants: £85 at Hellyhansen.com
6. Artilect Boulder Crew 125
Price: £84.99
Weight: 125g
Material: Nuyarn™ Merino Wool
Artilect astonished us with the Boulder Crew 125. It was the lightest base layer that we tried at 25g, but the weight was no reflection on warmth. It almost felt flimsy to put on and sat against my torso like a second skin. Being made from Nuyarn Merino Wool meant that it had all the warming properties of Merino Wool, but at almost half the weight.
It was fully moisture-wicking and dried more quickly than regular Merino wool. I wouldn’t recommend it for snow sports (it’s too thin for that), but it is an incredibly versatile option for thru-hiking and trail running.
I loved the look of it too – the exposed seams made me feel as though we were on a mountain catwalk runway. It came with all the design features that you’d want (including thumb loops). For ultralight fans, this one is going to be a must.
Full Specifications
Nuyarn merino fabric / ultra lightweight / eyelet knit for increased breathability / moisture-wicking / thumb loops / slim fit / flatlock seams.
Buy The Artilect Boulder Crew 125: £84.99 at Ellis-brigham.com
7. Megmeister Drynamo Winter Turtleneck
Price: £80
Weight: TBC
Material: 44% polypropylene, 44% nylon 6.6, 12% elastane
The big sister of the Megmeister Drynamo base layer, this one would be more suited to thru hiking and very cold conditions. I think the turtle neck is a fantastic design feature and saves the need to carry a buff.
This was thicker than many of the other base layers that I tried, and this was noticeable with the level of warmth that it provided. The ventilation was superbly designed, with plenty of breathability particularly on the back of the top, making it a great layer to pair with a backpack. Another great design feature with both of the Megmeister base layers is that they’re completely seam free, meaning that there’s no risk of chafing.
Full Specifications
Body mapped design with ventilation / ultralight / anti-odour and antibacterial function / thumb loops / light compression fit / moisture-wicking / 4 way stretch / seam free.
Buy The Megmeister Drynamo Warm Turtleneck: £80 at Shop.megmeister.com
8. Patagonia Capilene Thermal Weight Bottoms
Price: £90
Weight: 139g
Material: 129g Polartec Power Grid 92% recycled polyester, 8% elastane jersey with HeiQ pure odour control and an anti-pilling finish
The Patagonia Capilene thermal bottoms are made primarily from Polartec Power Grid fabrics. This, in case you didn’t know, is an innovative fabric that uses hydrophilic fibres that lift sweat away from the skin, ready to be dried quickly. It’s also knitted in an impressive grid-like structure that features hundreds of tiny insulating squares to keep you toasty and warm. Here, in true Patagonia fashion, they’ve also used recycled fabrics that are both bluesign approved and Fair Trade factory approved. All in all, an impressive effort.
During our tests, we found the Capilene thermal bottoms to be an great addition to our kit list. OM tester Jazz said, “I really loved how multi-function these thermals are. While great for a well-layered winter trekking outfit, I also found them to be perfect for getting cosy in your tent. I also really liked the gusseted crotch which made it super easy and comfortable to really move around in the mountains, and lean into ascents.”
Full Specifications
XS to XL / slim fit / Polartec Power Grid with HeiQ odour control / bluesign approved fabric / Fair Trade certified factory / flat waistband with brushed inner elastic / gusseted crotch / flatlock seam construction.
Buy The Patagonia Capilene Thermal Weight Bottoms: £90 at Eu.patagonia.com
9. Smartwool All-Season Merino Crew
Price: £80
Weight: 154g
Material: Merino wool, nylon
Being 88% Merino wool, the Smartwool all-season merino base layer provided excellent levels of warmth. It’s not the lightest Merino wool base layer on this list, but I did notice the extra layer of insulation and stayed toasty warm all day.
I’d thoroughly recommend this as a base layer for multi-day adventures at altitude or in cold conditions. Being Merino wool, we can also vouch for the fact that you won’t smell when you return home!
Here’s our review of the men’s version if you fancy a read.
Full Specifications
Flat lock seams / merino wool / body enhancing fit / moisture-wicking / interlock knit / odour resistant.
Buy The Smartwool All-Season Merino Crew: £80 at Smartwool.co.uk
10. Mammut Aconcagua ML Tights
Price: £75
Weight: 185g
Material: Polartec® Power Stretch® (33% Polyamide, 57% Polyester, 10% Spandex)
Legs get cold too, and we love it that Mammut has designed such a fantastic base layer to keep our bottom halves comfortable in low temperatures too. The Aconcagua ML tights were slim fitting which kept air close to the body and made them extremely insulating. The double-sided knit structure also means that they’re not going to go baggy over time (everyone’s worst fear with leggings).
They felt like a really robust, durable product which would be equally comfortable to wear on a run as on a thru-hike. All in all, I couldn’t believe that such warmth and quality had been achieved on such a lightweight piece of kit.
Full Specifications
Super-abrasion-proof nylon surface / elastic waist / abrasion resistance / moisture regulation / double-sided knit structure to keep shape / slim fit.
Buy The Mammut Aconcagua ML Tights Long: £120 at Mammut.com
How To Choose A Baselayer
The biggest factors to take into account when deciding which base layer to choose are activity and environment. A trek in the high Himalayas, for example, will require a different level of insulation to what you’d need for winter trail running in the UK. Of course, there are base layers that act as great all-rounders, and we’ve tested these too.
Fit is important. To optimise warmth, make sure that you get something that fits you snugly. If your base layer is hanging off you, it will be letting lots of air in. Plus it will be trickier to layer clothing on top.
Moisture-wicking fabrics absorb very little water and draw sweat away from the body. This means that often lightweight base layers made from moisture-wicking fabric can provide much more warmth than their heavier counterparts, because they don’t retain water.
The original version of this article was written by Anna Richards. Recent updates have been made by OM editorial assistant and gear tester Jazz Noble.
Cover Photo: Finisterre
Thumbnail Photo: Megmeister
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