Whether you’re hiking a mountain, hitting the slopes, or simply navigating a chilly commute, the foundation of your comfort begins with what’s closest to your skin.
Merino wool base layers, sometimes referred to as Merino thermals, have revolutionized outdoor performance wear, offering unparalleled natural benefits that synthetic alternatives can’t match.
This guide will help you understand why Merino wool deserves a place in your wardrobe and how to select the perfect base layer for your needs.
Fabric
Base layers come in a variety of fabric compositions and gsm weights, but 100% Merino wool stands out as the best choice for performance and comfort. Unlike synthetic blends, pure Merino wool offers natural breathability, exceptional moisture management, and superior odour resistance.
Some base layers blend merino with synthetic fibres such as polyester, nylon, or elastane to enhance durability, stretch, and drying speed. These blends can provide added resilience, making them suitable for high-intensity activities where durability is a priority.
However, they often sacrifice some of Merino’s natural benefits, such as its ability to regulate temperature and resist odours. Other compositions include merino-silk blends, which add an extra layer of softness and luxury, or merino-bamboo blends, which enhance breathability and eco-friendliness.
Merino wool from New Zealand and Australia is particularly prized for its superior quality, with the harsh alpine environments producing exceptionally fine, soft fibers (16-19.5 microns) that enhance the performance and comfort of premium base layers.
Choosing a 100% merino wool base layer ensures maximum softness, warmth, and sustainability.
The Benefits of Merino Wool
Merino wool is a powerhouse of performance fabric, known for:
- Moisture-Wicking: The fibres absorb sweat and transport it away from the skin, keeping you dry.
- Breathability: Unlike synthetics, Merino regulates body temperature, keeping you warm in the cold and cool in the heat.
- Odour Resistance: The natural antibacterial properties prevent odour buildup, allowing you to wear it for multiple days without washing.
- Softness: Fine Merino fibres are much softer than traditional wool, eliminating itchiness and irritation.
- Sustainability: As a renewable resource, Merino wool is biodegradable and environmentally friendly.
- UV Protection: Merino wool provides natural UV protection with a natural UPF rating of 30-50+, shielding your skin from harmful sun exposure even during extended outdoor activities.
Layering
Layering is essential for maintaining optimal body temperature in changing conditions. A Merino thermal base layer serves as the foundation for an effective layering system by:
- Wicking moisture away from the skin to prevent dampness and chill.
- Providing insulation by trapping warm air close to the body.
- Enhancing versatility when paired with mid-layers and outer shells for varying climates.
How to Layer Effectively
- Base Layer (Merino Wool) – Wicks moisture and regulates temperature.
- Mid Layer (Fleece or Insulated Jacket) – Traps heat while allowing breathability.
- Outer Layer (Shell Jacket) – Protects against wind, rain, and snow.
Choosing the Right Weight for Different Weather Conditions
Choosing the correct weight for your Merino base layer is crucial for comfort and performance. The weight of the fabric is measured in gsm (grams per square meter), which determines warmth and thickness.
Weight
Merino base layers come in different weights, ranging from ultralight to heavyweight:
- 120-150 gsm (Ultralight): Ideal for warm climates and high-intensity activities like running and cycling.
- 160-200 gsm (Lightweight): A versatile option for mild to cool temperatures, perfect for hiking and everyday wear.
- 210-260 gsm (Midweight): Provides extra warmth for colder conditions and winter sports.
- 320+ gsm (Heavyweight): The warmest option, best suited for extreme cold or low-activity settings.
The garment weight you choose might be based on the temperature as well as your pack weight.
Style
Merino base layers are available in various styles to suit different needs:
- Short Sleeve T-Shirts: Great for warm-weather activities or as a light base layer.
- Long Sleeve Shirts: Provide additional warmth and coverage for colder temperatures.
- Hooded Base Layers: Offer extra insulation and protection against the elements.
- Quarter-zip: Typically a long sleeve with a higher neck and a quarter zip.
- Long Johns & Leggings: Essential for full-body warmth in winter sports and outdoor adventures.
- Various Cuts & Colors: From slim-fit to relaxed cuts, Merino base layers and Merino Thermals come in a range of designs and colours to fit personal preferences and fashion choices.
Our Favorite Merino T-Shirts / Baselayers
Kathmandu – KMDMerino Baselayer Long Sleeve Top – Men’s and Women’s styles.
I recently picked up the men’s KMDMerino Baselayer Long Sleeve Top in black, and I’ve been thoroughly impressed with its performance. Made from 100% Merino wool, this shirt is a game-changer for anyone who values comfort and functionality. I wore it on a chilly early spring hike, and it kept me warm without overheating, thanks to its natural heat-regulating properties. The moisture-wicking feature worked like a charm too—I stayed dry even after working up a sweat. Plus, the odour resistance is a real bonus; after a long day outdoors, it still smelled fresh, which is more than I can say for most synthetic layers I’ve tried.
The design is another standout feature. The rib fabric construction gives it a nice stretch, so it moves with you rather than feeling restrictive—perfect for anything from hiking to just lounging around on a cool evening. The thumb loops are a thoughtful touch, keeping the sleeves in place when I layer it under a jacket. I also appreciate the flat seams and next-to-skin fit; there’s no chafing or irritation, even after hours of wear. It’s lightweight yet warm, which makes it versatile enough to wear as a base layer or on its own. Knowing there’s a women’s version in the same style is great too—my partner’s already eyeing one for herself!
Shipping was quick, and it arrived in perfect condition, unlike one reviewer who mentioned a damaged box—luckily, I didn’t have that issue. Overall, this top has earned a permanent spot in my wardrobe, and I’d recommend it to anyone looking for a reliable, high-quality layer for cool weather.
DHB Merino Short Sleeve Base Layer M150 – Women’s and Men’s
I have used these DHB Merino base layer t-shirts for over 10 years. They are the perfect weight for cycling
You can pick these up at a great price on Wiggle and they are available in various colours and styles for men and women.
Merino Skins – Unisex Merino Short Sleeve T Shirt
Best for Unisex and Overall
230 gsm – 100% Merino wool
I recently got my hands on the Merino Skins Unisex Merino Short Sleeve T-Shirt in black, and it’s quickly become one of my favourite pieces of activewear. Crafted from 100% fine Australian Merino wool at a mid-weight 230 gsm, this shirt strikes an impressive balance between style and performance. I’ve worn it for everything from morning runs to casual weekend hikes, and it’s been a standout every time.
The thermoregulation is no joke—on a brisk day, it kept me cozy, and during an unexpectedly warm afternoon, it wicked away moisture to keep me cool and comfortable. It’s like having a built-in thermostat, perfect for someone like me who’s always on the move.
The functionality of this shirt is top-notch. The superior wicking abilities really shine during workouts—sweat gets pulled away from my skin and evaporates fast, leaving me dry even after a solid session. I was sceptical about the odour-absorbing claim, but after a long day of wear, it still smelled fresh, which is a huge plus compared to some of my synthetic tees that start to stink after a few hours. The flatlock shoulder seams are a small but appreciated detail—no chafing, even with a backpack on.
And the fact that it’s unisex is brilliant; I grabbed a medium (which aligns with a women’s large), and the fit is spot-on, though checking the size chart is a must.
What seals the deal for me is the quality and practicality. Made in Australia with natural, environmentally friendly fibres, it feels good to wear something that’s both high-performing and sustainable. The double knit interlock fabric is soft yet durable, and I love that it’s machine washable and dryable—care couldn’t be easier. It’s also got UV protection, dries quickly, and is static-free, which are all bonuses I didn’t even realise I’d appreciate so much. Whether you’re a guy or gal looking for a versatile base layer that looks sharp and works hard, this Merino Skins t-shirt is a solid investment. I’m already tempted to grab another one!
Available in black or white.
Ridge Journey Merino Wool T-shirt
Best Travel Merino
145 gsm – 87% Merino wool blend
I’ve been wearing the Men’s Journey Merino Wool T-shirt in Black for a few weeks now, and it’s a solid piece of kit. The 87% Merino wool blend with a bit of nylon makes it soft and tough—good for hiking or just kicking around at home. It’s got a slim, slightly longer fit that feels modern without being tight, and the lack of flashy logos keeps it low-key, which I like.
It handles sweat well, dries fast, and doesn’t hold onto smells, even after a long day outdoors. The temperature regulation is legit too—kept me comfortable on a chilly morning and didn’t overheat when the sun came out. The taped, double-stitched seams haven’t budged, and at 5.2oz for a medium, it’s light but substantial.
The natural sun protection (30-50 UPF) is a nice bonus for sunny days. Overall, a reliable shirt that works for pretty much anything without much fuss.
Whether you’re hitting the slopes, going on a hike, or just looking for everyday comfort, Merino wool remains the best choice for performance and sustainability.