Men’s thermal leggings, often called base layer bottoms or long johns, are an essential foundation for staying warm in cold weather without. At Barefoot Backpackers, we always opt for trusty merino wool as not only is it an excellent perforamance fabric, but it is also a natural fiber that is breathable, lightweight, and helps to resist lingering odors too. Designed to sit close to the skin, merino wool base layers trap body heat while allowing moisture to escape, keeping you dry and comfortable whether you’re hiking, skiing, running, or simply layering for winter travel.
Modern thermal leggings are most commonly made from merino wool, a natural fibre known for its exceptional temperature regulation, odour resistance, and softness. Unlike synthetic thermals, merino wool adapts to changing conditions, keeping you warm when it’s cold and breathable when you’re active. That’s why we love opting for merino wool underwear, socks, and clothing.
In this guide, we’ve selected the best men’s thermal leggings for different needs, from lightweight everyday layers to midweight cold-weather options and budget-friendly picks. We’ve also included key details like fabric thickness and weight category so you can easily choose the right pair for your climate and activity level.
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At a Glance: Best Men’s Thermal Leggings
- Best Overall: Smartwool Men’s Merino 250 Baselayer Bottom
- Best Lightweight Option: Icebreaker 175 Everyday Leggings
- Best Budget Pick: MERIWOOL Thermal Pants
- Best Active Merino Leggings: SmartWool Mens Active Fleece Wind Tights
- Best 3/4 Length: Smartwool Classic Thermal 3/4 Bottom
- Best Value Set: Merino.tech Base Layer Pants
- Best Everyday Comfort: Icebreaker Standard 175 Leggings
Best Men’s Thermal Leggings
This midweight base layer offers excellent warmth for cold climates while maintaining breathability and comfort. The full-length design provides consistent insulation from waist to ankle.
Flatlock seams prevent irritation, and the contoured fit makes them easy to wear under snow pants or hiking trousers.
Key specs
100% merino wool
Fiber thickness approx 18.5 microns
Weight midweight 250 gsm
Full length design
Moisture wicking performance
These Merino.tech base layer pants are designed for reliable warmth in cold conditions while maintaining breathability. Made from superfine merino wool, they offer soft insulation that feels comfortable against the skin and naturally regulates temperature.
Available in multiple weight options, they adapt to different climates and activities. The included merino wool socks add extra value, making this a practical starter thermal set for outdoor adventures.
Key specs
100% superfine merino wool
Available in:
Lightweight = 165 g/m²,
Midweight = 250 g/m²
Heavyweight = 320 g/m²
Includes merino wool socks
Machine washable
These 3/4 length thermal leggings are designed to sit comfortably above ski or hiking boots, preventing bunching and improving mobility. The interlock knit provides soft insulation while remaining breathable during active use.
Ideal for skiing, winter hiking, or mountaineering, they deliver dependable warmth and moisture management in demanding cold-weather environments.
Key specs
100% merino wool
Midweight: 250g/m, Slim Fit
Weight category
3/4 cropped length
Flatlock seams
Lightweight and breathable, these leggings are ideal for year-round layering. The ribbed merino knit enhances stretch and airflow, making them comfortable for active movement.
A brushed elastic waistband ensures a secure fit, while the natural fibres wick moisture and resist odour for extended wear.
Key specs
100% merino wool rib knit
Fiber thickness approx 18.9 microns
Weight lightweight 175 gsm
Slim contoured fit
Breathable and odor resistant
If you are a runner, hiker or simply looking for a pair of merino lined tights that are also windproof, then this is a great fit. The slim fit is intended to follow the contours of the body. The leggings are lines with soft-brushed Merino next to skin and durable recycled synthetic material against the elements to help balance comfort and protection.
It includes a-PFC DWR finish help protect from the elements Interior waist drawcord for adjustable fit and ankle zips
Key specs
Merino lined
Main Body: 47% Recycled Polyester, 38% Merino Wool, 15% Elastane
Full length design
Windproof front panel (1CFM rating) and merino lined
Secure zippered pocket at rear and drop-in pocket on side panel Reflective elements
These lightweight leggings are perfect for layering in mild to cool conditions. The merino wool fabric provides warmth without bulk while maintaining excellent breathability.
Flatlock seams and a contoured pouch enhance comfort, making them suitable for everyday wear as well as outdoor activities.
Key specs
100% merino wool
Fiber thickness approx 18.9 microns
Weight lightweight 175 gsm
Slim next-to-skin fit
Flatlock seam construction
These budget-friendly thermal leggings offer dependable warmth and softness without sacrificing performance. The merino wool fibres wick moisture and regulate temperature effectively.
Quick-drying and easy to care for, they are a practical choice for hiking, travel, or everyday winter layering.
Key specs
100% merino wool
Fiber thickness 18.5 microns
Weight midweight 250 gsm
Next-to-skin fit
Machine washable
Although not thermal leggings, these merino boxers make an excellent base layer foundation. Their ultralight fabric provides softness, breathability, and odour resistance.
The tagless design and flatlock seams prevent irritation, making them ideal for long days of hiking or travel.
Key specs
100% ultralight merino wool
Fiber thickness approx 18–19 microns
Weight category lightweight
Flatlock seam construction
Moisture wicking performance
How to Choose Men’s Thermal Leggings
When choosing thermal leggings, consider fabric weight, fibre thickness, and activity level. Lightweight options (150–175 gsm) are best for active use, while midweight fabrics (200–250 gsm) provide greater insulation for cold conditions. Fibre thickness also matters. Finer microns feel softer and more comfortable against the skin.
Understanding Lightweight, Midweight, and Heavyweight Merino Thermals
Merino wool thermal leggings are typically categorised by fabric weight, measured in grams per square metre (gsm). This number indicates how dense and insulating the fabric is, which directly affects warmth, breathability, and ideal use conditions.
Lightweight merino thermals (150–175 gsm) are best suited for high-output activities and mild to cool weather. They provide gentle insulation while allowing excellent airflow, making them ideal for running, hiking, travel, or everyday layering. Because they are thinner, they also dry quickly and feel less bulky under clothing.
Midweight merino thermals (200–250 gsm) offer a balance of warmth and breathability, making them the most versatile option. They work well in cold climates, winter hiking, skiing, and general outdoor use. Midweight thermals retain more heat than lightweight versions while still regulating moisture effectively during activity.
Heavyweight merino thermals (300 gsm and above) are designed for extreme cold conditions. These thicker fabrics provide maximum insulation and are ideal for mountaineering, winter camping, or long periods of low activity in freezing temperatures. However, they can feel too warm during high-intensity movement.
FAQs
Are merino wool thermal leggings worth it?
Yes. They provide superior warmth, moisture control, and odour resistance compared to synthetic materials.
What weight should thermal leggings be?
Lightweight for active use, midweight for cold climates, and heavyweight for extreme winter conditions.
Can you wear thermal leggings on their own?
Yes, especially lightweight merino styles, which are breathable and comfortable enough for lounging or sleeping.
