Choose your merino base layer by matching fabric weight (gsm) to the temperature, then fit to your activity. For most New Zealand conditions, midweight (190–250 gsm) is the right starting point — warm enough for winter, breathable enough for summer hikes.
Use the guide below to pick the right weight, fit and style for what you actually do.
What is gsm in merino base layers?
Gsm stands for grams per square metre — the weight of the fabric. The higher the gsm, the warmer and thicker the layer. It is the single most important spec when comparing base layers.
- Lightweight: 130–190 gsm. For warm or mild conditions and high-output activities (running, fast hiking, summer tramping).
- Midweight: 190–250 gsm. The all-rounder. Skiing, three-season hiking, everyday winter wear.
- Heavyweight: 250+ gsm. Alpine cold, low-output use (camping, lounging, winter desk work).
What weight merino should I wear for hiking?
For day hikes in summer or shoulder season, choose lightweight (130–190 gsm). For winter day hikes or multi-day tramps with cold mornings, go midweight (190–250 gsm). For alpine huts or sleeping layers in winter, add a heavyweight piece on top of your active layer.
What weight merino should I wear for skiing or snowboarding?
Midweight (190–250 gsm) is the most popular ski base-layer choice in New Zealand. It handles the temperature swing between standing in the lift queue and a hot run down. If you ski mostly in spring or you run hot, drop to lightweight; if you're chair-lift skiing in deep winter, go heavyweight.
What weight merino should I wear for running and cycling?
Lightweight (130–190 gsm). High-output activities generate a lot of heat, and you want the fabric to breathe and wick vapour as fast as possible. A short-sleeve or singlet is often enough even in cool weather once you're moving.
How should a merino base layer fit?
Snug, but not tight. The fabric needs to be in contact with your skin to wick moisture — a baggy base layer doesn't work. It should not restrict movement or pinch at the shoulders, waist or armpits. If you're between sizes, size down for performance, size up for comfort.
Should I get a long sleeve, short sleeve, or singlet?
- Long sleeve: the most versatile piece. Layers under almost anything, works year-round in NZ.
- Short sleeve / T-shirt: for warmer conditions or as a sole layer in summer.
- Singlet: high-output activities or extra warmth without bulk under shirts.
Should men and women buy different cuts?
Yes. Men's and women's merino base layers are cut differently to follow body shape, especially through the chest, hip and waist. A correctly cut base layer wicks better and lasts longer because it doesn't ride or stretch in the wrong places.
Frequently asked questions
What's the most versatile merino base layer to own?
A midweight (190–250 gsm) long-sleeve top. It handles three out of four New Zealand seasons and works for hiking, skiing, travel and everyday winter wear.
Can I wear a merino base layer on its own?
Yes — a short-sleeve or long-sleeve merino top works as a regular shirt. That's part of why merino travels well: the same garment can be a base layer or a top layer.
How many merino base layers do I need?
Two of any active piece is usually enough. Merino's natural odour resistance means you can wear a base layer for several days between washes, so two pieces in rotation cover most needs.
Is 100% merino better than a merino blend?
For next-to-skin comfort, breathability and odour resistance, 100% merino is the gold standard. Some blends add nylon or elastane for stretch and durability in high-wear areas, which has its place — but the more synthetic in the blend, the more you lose merino's natural performance.
Shop merino base layers by weight
Browse the full Brass Monkeys merino range. New to merino? Start with a midweight long-sleeve top — for most people in New Zealand it's the single most useful piece in the wardrobe.
