Base layer buying guide
Discover how to choose the right base layer to keep you cozy, dry and active in any weather.
Love getting outdoors but the cold makes you think twice? Whether it’s a winter walk, a ski trip or a chilly morning run, that icy air can quickly impact your mood. The good news? The right base layer changes everything. It keeps you warm, dry and comfortable so you can focus on the adventure, not the temperature. In this guide, we’ll break down what a base layer is, how it works and how to choose the perfect one for you.
Base layers 101: What they are and why they matter
A good base layer is where every cold-weather outfit begins. Worn closest to your skin, it works hard to regulate your body temperature and wick away sweat, keeping you warm without feeling stuffy. Think of it as the foundation of comfort.
Layering made simple: Where base layers come in
Now that you know what a base layer does, it’s easier to see how it fits into the bigger picture. The layering system is all about staying warm, dry and comfortable outdoors. Here, each layer has a distinct role:
Base layer: Your first line of defence. It keeps you dry and helps regulate your temperature, so you stay cozy without overheating
Mid layer: This layer traps body heat. Fleece, down or similar fabrics help retain warmth without adding too much bulk
Outer layer: Your shield against wind, rain and snow, keeping the elements at bay while letting the layers underneath do their job
Tip: When layering up for the outdoors, choose a base layer that sits comfortably under your mid and outer layers to avoid discomfort or bulkiness.
Choosing your fabric: Merino, synthetics and blends explained
When it comes to choosing a good base layer, the material matters most. The right fabric can make all the difference. Below is a breakdown of the most common types:
Merino wool base layers
Merino wool is naturally soft, warm and breathable, keeping you comfortable and fresh in cold conditions.
Why you’ll love it: Feels soft against your skin, naturally resists odor by preventing bacteria build-up and keeps your temperature just right. Perfect for ski trips, hiking, traveling or layering up for everyday cold weather.
What to look out for: Can be a little delicate and usually costs more than synthetics.
Synthetic base layers
Synthetic fabrics like polyester and nylon are built to wick away sweat and dry quickly, making them perfect for high-energy days.
Why you’ll love it: Durable, lightweight, quick-drying and easy on the wallet. Ideal for running, cycling, gym sessions or any high-intensity outdoor activity.
What to look out for: They can hold onto odors and might not feel quite as soft or natural against the skin.
Blended base layers
Blends combine the softness of Merino wool with the strength and stretch of synthetics, giving you the best of both worlds.
Why you’ll love it: Warm, comfy, moisture-wicking and more durable than pure wool. Best for everything from active adventures to relaxed weekend getaways.
What to look out for: Slightly pricier than pure synthetics and may need gentle washing to keep them in good condition.
Did you know? Some styles in our HeatIQ are made with responsibly sourced fabrics like 50% cotton from the Primark Cotton Project, 50% sustainable viscose and 50% recycled polyester.
Understanding base layer weights and warmth
Weight is all about the thickness or density of the fabric, while warmth is how well it keeps you cozy. The same weight can feel warmer or cooler depending on the material; Merino wool, synthetics and blends all perform differently.
Base layers usually come in three weights:
Lightweight (150-200gsm): Thin and breathable, perfect for high-energy days or milder weather
Midweight (200-250gsm): A bit thicker, offering a balance of warmth and comfort for moderate cold or layering under jackets
Heavyweight (250+gsm): Thick and insulating, ideal for freezing temperatures or slower, low-activity days
Our HeatIQ range also makes it simple to pick the right warmth levels to suit your day, activity and the weather, thanks to our Warm, Extra Warm and Max Warm product capsules.
Tip: Choose the right weight and warmth for your activity and the conditions to stay comfortable without overheating.
What features to look for in a base layer
Beyond fabrics, weight and warmth, a base layer’s breathability, seam construction and moisture management capabilities can make a big difference to its performance. They depend on the fabric quality, construction, fit and any special finishes. While these features aren’t the same across every base layer, keeping an eye out for them will help you choose one that feels great all day.
Moisture-wicking technology and quick drying time: A good base layer draws sweat away from your skin with its moisture-wicking technology, moving it to the outer surface. The quick-drying fabric then helps it evaporate faster, keeping you dry, cozy and comfortable, even during long days outdoors
Breathability and odor resistance: Materials that promote good air circulation stop you from overheating and help sweat dry faster, reducing the chance of odor build-up. Merino wool naturally stays fresh, while many synthetic styles are treated to keep you feeling clean for longer.
Seam construction: Because base layers sit right against your skin all day, good seam construction is key. Flatlock or minimal seams reduce rubbing and chafing, keeping you comfortable and free to move. Plus, with smooth seams, the layer can retain heat properly without causing irritation
Finding your perfect base layer for every adventure
Picking a base layer can feel tricky. There are so many factors to consider, from activity and weather to fit and fabric. The simple three-step approach below will help simplify the process:
Step 1: Pick your adventure
High-intensity activities
Think skiing, fast-paced hikes or anything that gets your heart racing. Naturally, an increased heart rate leads to a higher body temperature so staying dry matters more than piling on warm clothes. Breathable, moisture-wicking fabrics stop you from overheating when the pace picks up.
Recommended: Lightweight or breathable midweight base layers, like our HeatIQ Warm options are perfect for extra comfort without bulk.
Medium-intensity activities
During steady runs, cycling sessions and workouts, you heat up gradually, meaning you need a bit of everything: warmth to start with, breathability as you build heat and quick-drying fabric to keep you comfy. It’s all about balance.
Recommended: Versatile midweight layers such as our HeatIQ Extra Warm pieces are great picks for all-round performance.
Low-intensity activities
Slower-paced activities like the school run, chilly commutes and weekend markets don’t generate lots of body heat. Here, insulation becomes key, helping you stay snug when you’re standing around or strolling slowly.
Recommended: Look at warmer thermals such as HeatIQ Max Warm for cozy comfort on cold days.
Step 2: Check the weather
Colder days or slower activities? Go for a heavier layer. Mild weather or high-energy days? A lighter layer keeps you moving comfortably.
Step 3: Get the right fit
A close, body-hugging fit works best for warmth and moisture control. Anything too loose can trap sweat and leave you feeling chilly.
Tip: Always try before you buy a base layer. Check the fit, move around and see how it feels under other layers to make sure it’s comfortable.
Looking after your base layer
Keeping your base layers in top shape is easier than you think. Here’s how to look after them so they can last longer:
Wash in cold water: A gentle cold wash keeps fabrics intact and stops shrinking while still getting rid of sweat and odors
Air dry: Skip the dryer when you can. Hanging your base layers to dry keeps their shape and performance at their best
Follow care instructions: Every base layer comes with its own care tips. Following them helps maintain softness, warmth and moisture-wicking properties
FAQs
Why avoid cotton base layers?
- Cotton holds onto moisture instead of wicking it away, so you end up feeling damp and chilly instead of warm and dry.
How should a base layer fit?
- Snug but not tight, it should feel like a gentle hug that moves with you and sits comfortably under other layers.
What is the difference between a base layer and mid layer?
- Your base layer keeps you dry and comfy, while your mid layer locks in warmth on top.
Can I wear a base layer alone?
- Absolutely, many styles look great worn solo for lounging or layering light on milder days.
Are seamless base layers worth it?
- Yes, seamless styles usually decreases the chance of rubbing and chafing, giving you smooth comfort from morning to night.
Are there differences between mens, womens and kids base layers?
- Mostly in fit and cut; each is designed to suit different body shapes and comfort needs but they all do the same job.
Do base layers help in summer?
- They can! Lightweight, moisture-wicking ones keep you cool and dry when you’re active in warm weather.