Best base layer 2024: Add warmth without the bulk

Find the best Merino and synthetic base layers to keep you comfortable whatever the weather

best base layer: pictured here, a hiker doing up his hiking backpack straps
(Image credit: Klattermusen)

In winter, having the best base layer is essential for outdoor activities, ensuring comfort in fluctuating temperatures. Whether hiking or camping, these close-fitting layers provide insulation and sweat-wicking properties for optimal performance.

Designed to be stretchy and comfortable, base layers facilitate seamless layering without adding bulk. With our roundup of the top base layers, you'll be well-equipped for any chilly adventure, allowing you to enjoy the outdoors without worrying about discomfort.

As you've probably guessed, the base layer is the first of many thin layers you can put on or take off as needed to maintain a comfortable temperature. As such, if you're out hiking, you could add a fleece jacket with one of the best waterproof jackets on top to ensure you have plenty of options depending on the weather and how much you exert yourself.

Our current top choice for the base layer is Arc’teryx's Rho Hybrid Half Zip top. It's extremely versatile and comfortable – a superb base layer overall. If you need to wick sweat fast, you can't go wrong with the Helly Hansen LIFA top listed in second place. If you're on a tight budget but don't want to compromise too much on quality, check out the BAM Reflex Bamboo Base Layer.

Best base layers to buy right now

Why you can trust T3 Our expert reviewers spend hours testing and comparing products and services so you can choose the best for you. Find out more about how we test.

Best overall

Arc’teryx RHO LT Hoody

(Image credit: Arc’teryx)

1. Arc’teryx RHO LT Hoody

Best base layer overall

Specifications

Weight: 270g / 9.5 oz
Materials: Torrent 190 with Polygiene- 84% polyester, 16% elastane
Fit: Athletic

Reasons to buy

+
Really versatile base layer
+
Lightweight but warm
+
Built in hood/balaclava 

Reasons to avoid

-
No thumb loops
-
Very expensive for manmade materials 

We have previously waxed lyrical about Arc’Teryx base layers, purely because they appear to have been born out of the coldest conditions and can therefore withstand anything most ‘regular’ winters can throw at them.

The RHO LT Hoody is part of the lightweight collection, so feels featherweight against the skin and almost invisible when layered up as part of a proper outdoors layering system. The brushed stretch polyester is also a nice touch for added comfort.

Arguably its most unique selling point is the built in neck warmer, which can also extend to become a hood or full coverage balaclava during those whiteout days where protection from the elements is vital.

It’s up there with the best thanks to a few careful considered features, such as the easy access smartphone pocket on the chest and the athletic fit that stretches and moves with the body, making it great for running, climbing and a number of other outdoor pursuits.

Best moisture management

Helly Hansen LIFA Merino Lightweight Half Zip Baselayer review

(Image credit: Matthew Jones)

2. Helly Hansen LIFA Merino Lightweight Half Zip Baselayer

Best base layer for moisture management

Specifications

Weight: 235g/8.3oz
Materials: Shell: 70% Merino Wool, inner 30% Polypropylene
Fit: Athletic

Reasons to buy

+
Warm and wicks moisture fast
+
Soft and comfortable
+
Odour-resistant

Reasons to avoid

-
No thumb loops

We found that the Helly Hansen LIFA Merino Lightweight Half Zip Baselayer excels in comfort, fit, and performance. This lightweight baselayer combines synthetic LIFA fibres with merino wool for effective moisture management and lightweight warmth.

Design features include a soft-backed neck zip, flatlocked seams, and a snug fit. It performed well in cold conditions, keeping us dry and comfortable during high-output activities.

While it lacks thumb loops, it remains odour-resistant and durable after multiple uses. Ideal for active outdoor pursuits, it’s a reliable choice for staying warm and dry.

Read our full Helly Hansen LIFA Merino Lightweight Half Zip Baselayer review.

Best budget

Bam Reflex Bamboo base layer

(Image credit: BAM)

3. BAM Reflex Bamboo Base Layer

Best budget base layer

Specifications

Weight: TBC
Materials: Bamboo viscose, cotton, elastane
Fit: Active

Reasons to buy

+
Sustainably made
+
Thumb loops
+
Breathable, soft fabric

Reasons to avoid

-
Quite tight-fitting for recreational use

BAM specialises in clothing made from bamboo, often with other fibres blended in for maximum comfort, durability and performance while still being as eco-friendly as possible (this brand is responsible for some of the best yoga pants around). Of its base layer options, our pick is the Reflex, which uses bamboo jersey with its soft, breathable, sweat-wicking and anti-bacterial.

The design is cut longer in the body and arms to ensure everything stays covered even when you're moving around a lot – there are even thumb loops for when it's chilly. Flatlock seams and raglan sleeves minimise chafing. Even though it's longer to keep your lower back warm, BAM's top is more tight fitting than other base layers in this guide.

Best for hot weather

ThruDark Oryon Delta T-Shirt worn by male model

(Image credit: ThruDark)

4. ThruDark Oryon Delta T-Shirt

Best base layer for hot weather

Specifications

Weight: 180g (Men's medium)
Materials: Polartec Delta Cooling Fabric
Fit: Relaxed

Reasons to buy

+
Excellent moisture-wicking capabilities
+
Reduced cling
+
Highly breathable

Reasons to avoid

-
Feels thicker than standard base layers

ThruDark's short-sleeved base layer caught our attention thanks to its material. Polartec's Delta uses the Fresh Face technology, which is a plant-based, sustainable alternative to traditional textile fresheners and is infused with mint oil to keep you cool even on the hottest of days.

Thanks to the superb moisture-wicking capabilities and more relaxed fit, the Oryon Delta T-Shirt clings less to your body when you sweat. It feels somewhat thicker than other synthetic base layers, but once the temperature starts rising inside and outside the top, you'll soon feel the mint oil-powered cooling kicking in.

Best eco-friendly

Finisterre Seeker Merino

(Image credit: Finisterre)

5. Finisterre Seeker Merino

Best eco-friendly base layer

Specifications

Weight: TBC
Materials: 100% merino
Fit: Casual

Reasons to buy

+
Relaxed fit for casual wear
+
Available with long or short sleeves
+
Ridiculously comfortable

Reasons to avoid

-
Some questions over longevity
-
Not the most breathable

There is very little that’s quite as comfortable against the skin as 100 per cent merino wool and this range from UK brand Finisterre is fantastic as either a loose-fitting base layer or as a casual T-shirt.

It is only available in navy or olive, which limits the outfit paring somewhat, and it isn’t as athletic in its fit as others, so some may not want to purchase it as part of a complex layering system for climbing or winter walking, but it’s a great casual option.

Finisterre gear is built to last and carefully considered to reduce the impact of fashion on the plant, and the Seeker Merino is no exception. However, 100 per cent merino wool is delicate by its very nature, so requires careful washing and drying habits.

On that subject, merino has natural sweat-wicking and anti-odour properties, but this wasn’t up there with the most breathable base layers we have tested. As a properly technical garment, it’s not top of the pile, but as something more fashionable, easy to live with a exceptionally warm on a winter’s day, it is fantastic.

Best merino

best base layer: Icebreaker Tech Lite Short Sleeve Crewe

(Image credit: Icebreaker)

6. Icebreaker Tech Lite Short Sleeve Crewe

Best merino base layer

Specifications

Weight: TBC
Materials: 87% core-spun merino wool, 13% Nylon
Fit: Relaxed

Reasons to buy

+
Breathable and odour-resistant
+
Lightweight construction

Reasons to avoid

-
Short product lifecycle
-
Relaxed fit isn't ideal for exercise

Icebreaker's Tech Lite is a classic among frequent travellers and 'speedpackers' thanks to its odour-resistant capabilities and the fact it can be wrung out in a sink and dried in hours. It works great as a regular T-shirt (it's not as figure-hugging as most base layers), and, between you and us, you can wear an Icebreaker Tech Lite for days on end without getting too whiffy.

The only drawback is that Merino does lack longevity, which is why most brands don't get much beyond 50%. Expect this top to thin out and get holes after about a year or two of heavy use (top tip: keep it for hikes and holidays only). 

How to choose the best base layer for you

Choosing the best base layer is crucial for comfort and performance during outdoor activities.

Merino wool offers warmth, moisture-wicking, and odour resistance, while synthetic fibres like polyester are durable and quick-drying. Bamboo blends are eco-friendly and soft but may not dry as quickly.

Select a weight that matches your activity and climate. Lightweight base layers are ideal for high-intensity activities, such as hiking and trail running or mild weather, while midweight or heavyweight options provide extra warmth for cold conditions.

Consider features like thumb loops, half-zip designs for ventilation, and flatlock seams for added comfort. These small details can significantly enhance your experience.

Also, check the durability and care instructions. Some materials are more robust and easier to maintain, extending the lifespan of your base layer.

Reviewer panel

Matt Kollat

Matt looks after all things outdoors at T3, including outwear. He's a keen walker, runner, and cyclist and spends a lot of time outdoors all year round. As such, he gets to 'test' a lot of base layers, of which the best ones end up in this guide.

Jamie Carter
Jamie Carter

Jamie is a freelance journalist, copywriter and author with 20 years of experience. He spends most of his time travelling and staring at the skies (via a telescope), often in the cold, so he inevitably ends up testing base layers. It's only natural he writes about them, too.

Ruth Hamilton
Ruth Hamilton

Former Outdoor and Wellness channel editor, Ruth knows a thing or two about kit for an active lifestyle. Whether that's walking trousers, flip-flops or torches for lighting the way, Ruth has put it through its paces.

FAQ

What's the best base layer material?

There are many ingenious hybrid fabrics used in base layers, from carbon fibre to silver, but they can broadly be split into two camps: those made from merino wool and those created using synthetic fibres.

The famous (and expensive) Merino wool is warmer by weight, more comfortable and absorbs less body odour. Merino wool retains heat, it's breathable, so it allows sweat to escape, and as a bonus, it's naturally antibacterial, so it can be worn for days on end without needing to be washed. For general travel, it's unbeatable. However, traditionally, Merino wool fabrics don't last as synthetics.

Though there are many hybrids that use a mix of both, the other end of the spectrum is the wholly synthetic base layer. They tend to use various polyester blends that are also breathable but perhaps not quite as warm as Merino. Artificial materials tend to be hard-wearing and easier to engineer and body map. That means they're generally lighter and longer-lasting.

What is the warmest base layer material?

Merino wool, by far, is the warmest base layer material. This natural fabric also helps regulate heat better, as well as being swift-wicking and odour-resistant. For the most warmth, look for Merino base layers with 250-300g weight.

Are base layers better than thermals?

Base layers and thermals serve similar purposes but differ in material and functionality. Base layers, often made of synthetic fibers or merino wool, wick moisture away from the skin and offer breathability, making them ideal for active pursuits. Thermals, typically made from thicker materials, provide more insulation but may not manage moisture as effectively. As such, base layers are better for high-intensity activities, while thermals are suitable for extreme cold and low activity.

Matt Kollat
Section Editor | Active

Matt Kollat is a journalist and content creator who works for T3.com and its magazine counterpart as an Active Editor. His areas of expertise include wearables, drones, fitness equipment, nutrition and outdoor gear. He joined T3 in 2019. His byline appears in several publications, including Techradar and Fit&Well, and more. Matt also collaborated with other content creators (e.g. Garage Gym Reviews) and judged many awards, such as the European Specialist Sports Nutrition Alliance's ESSNawards. When he isn't working out, running or cycling, you'll find him roaming the countryside and trying out new podcasting and content creation equipment.