The Best Women’s Merino Wool Base Layers

When it comes to staying warm in the outdoors during winter, it is all about layering.  You can have a super high-tech (and super expensive) outer layer. But, if your base layer isn’t adequate, you won’t stay warm.   That’s where Merino wool base layers come in.

I personally have tried a lot of different long johns and thermal underwear.  Merino wool base layers are the only ones that:

  • Actually feel good against my skin
  • Keep me dry (I sweat profusely)
  • Don’t chafe during exercise
  • Can be worn in moderate to extremely cold weather
  • Don’t stink terribly

What about the alternative materials? Synthetic base layers always make me feel sweaty and gross – even those ones which supposedly are “wicking.” Synthetics also smell terrible after just a few hours of wearing. Cotton might be comfy, but you might as well be wearing a sponge because of how well they trap moisture!

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Top Picks

*Keep reading for more product recommendations, including lightweight and heavyweight Merino base layers.

**Tip: Check out REI Outlet for extreme discounts on Merino base layers.


Are Merino Wool Thermals Worth the Cost?

Merino wool base layers are a lot pricier than most synthetics.  However, your base layer is not something you want to skimp on.  It is the layer going directly against your skin.  If the base layer doesn’t do a good job of wicking away moisture and insulating, then you’ll end up cold and sweaty.

It won’t matter how good your jacket is: If your base layer fails, your entire layering system will fail! In this sense, yes it is worth the extra cost to get a good Merino wool base layer. I’m not the only one who thinks this.  You can read about backpackers’ and adventurers’ love affair with Merino wool base layers in this forum here,  and here.

Still not convinced?  Here are some of the reasons that Merino wool is worth the cost:

  • You can wear it in winter or summer: In winter, wool is one of the best insulators you can wear. But, since it is breathable, you can also wear it in the summer and stay cool.  The wool will provide UV protection.
  • Wool wicks away moisture: Wool will draw moisture away from your skin, which prevents evaporation which would cause heat loss.
  • It insulates while wet. Wool naturally has little pockets of air in it. These are what provide the insulation.  Even when wet, those little pockets of air will remain.  If you fall into a creek while winter hiking, a Merino wool base layer could be what gets you back to base safely.
  • Merino wool doesn’t stink: Ok, this is debatable. There are hardcore hikers who wear the same Merino wool base layer for days and claim they don’t smell.  Of course it stinks – it just doesn’t stink nearly as badly as synthetic base layers (which stink wretchedly!).
  • It is soft: Other types of wool have the same great insulating properties as Merino. However, they are itchy as hell.  That results in chaffing. 🙁  This doesn’t happen with Merino wool — especially with brands that make sure to put the seams in smart places.
  • Fairly durable: Compared to synthetic base layers, Merino wool isn’t that durable. But it does hold up very well – especially if you are getting midweight or heavyweight Merino wool.
  • Dries quickly: Lightweight Merino wool will dry in about 30-60 minutes when hung up. This means you can rinse it out at camp and have it clean and dry for the next day.
  • Great warmth-to-weight ratio: There is really nothing comparable to Merino wool when it comes to the warmth-to-weight ratio. Yes, synthetics are getting better – but they still feel like crap against your skin and make you stink.

These are what Merino sheep look like


100% Merino Wool or Blend?

A lot of base layers are made of 100% Merino wool.  However, you’ll also find thermals made of Merino with a blend of other materials.  This isn’t necessarily bad or good – it just depends on what properties you want.


Merino/Silk Blends:

Silk has the benefit of being very warm, incredibly soft, and very thin.  However, it isn’t very durable.  It also doesn’t do such a good job of wicking away moisture.  Plus, it is expensive.

*Choose silk blend thermals for: Casual wear, such as thermals to wear under your work clothes. Merino/silk blends are also great for panties.


Merino/Synthetic Blends:

Good synthetics have many of the same properties of Merino wool: they wick away moisture, they are very warm, and they dry very fast.  The only major benefit that synthetics have over Merino wool is that they are much more durable. That’s why virtually all wool socks contain some synthetics in the weave – socks get too much abuse to be pure Merino wool (read about the two-sock system for hiking here). The downside is that synthetics stink like crazy.

As far as synthetic blends go, polyester generally beats nylon!

*Choose synthetic blends for: when your clothing will take a beating, such as when being worn under a heavy pack.  Also choose in situations where you don’t worry about your stink offending people around you!


Merino Wool Thickness/Weight

Merino wool base layers come in different thicknesses and weaves.  These are suitable for different types of use or temperatures.   The thickness is measured in grams per meter squared, which tells you how much wool is in the fabric.


  • 120-150 g/m2
  • For warm to hot conditions
  • Usually a jersey knit
  • Doesn’t stand up to abuse well


  • 150-170 g/m2
  • Suitable for all year
  • Usually a single jersey knit
  • Dries in about 30-60 minutes


  • 170-200 g/m2
  • Suitable for all year, but provides more warmth
  • Good for high activity in moderately cool weather
  • Usually a double jersey knit


  • 200-300 g/m2
  • Interlock knit or double jersey knit
  • Wear at 30-60 degrees F during low activity
  • Wear at 0-30 degrees F during high activity
  • The most versatile option


  • 300+ g/m2
  • Interlock knit
  • Wear at 0 degrees F or below during low activity
  • Wear at 0-30 degrees F during high activity
  • Can be worn as a mid-layer


Merino Wool Brands:


Smartwool is the company responsible for popularizing Merino wool.  It started as a small brand made for skiing and has since grown to include lots of quality products specifically for outdoor use like backpacking. Their products are 100% guaranteed and they have a very good commitment to sustainability and ensuring their products are ethically sourced.  See selection at REI.


This is one of the most popular brands of women’s Merino wool base layers.  They are a fairly big company and operate under ethics of sustainability and animal welfare.  They have a cool feature called “Baacode” which allows you to track the origin of the wool in their clothing.  The company itself is based in New Zealand but their products are now manufactured in China. Socks are made in the USA. See selection at REI


REI has their own line of Merino wool base layer products.  I couldn’t find information about how they are sourced, but it’s likely they are made from another company and rebranded under the REI label.  This is a good pick for affordable, high-quality Merino base layers and they’ve got a lot of nice prints for women.  See selection here.


This company started in 2012 in San Francisco, primarily as a cloth diaper company.  Now they make a whole range of wool apparel.  Because they are a small company though, they don’t have that big of a selection for women’s base layers. As of writing, all of their women’s clothing is 70% organic Merino wool and 30% silk. Their prices are reasonable considering that the wool is organic. See options here on Amazon


Woolx makes 100% Merino wool base layers, marketed towards people who do outdoor sports. They offer a 100% satisfaction guarantee on their products. See options here


Janus is a wool products company which is based in Norway. They have apparently been around since 1895.  Janus makes almost everything you’d need to stay warm, including base layers, gloves, panties, hats, and baby clothes. Most of their products seem to be 98% Merino wool and 2% silk.  They also have other blends available. See options here


Minus33 is based out of New Hampshire.  They were started by textile engineers from the L. W. Packard Company, thus making them one of the bigger companies to offer women’s base layers. All their products are 100% Merino wool.  They use flatlock seams to reduce chaffing. Their products have a 1-year warranty and a 30-day satisfaction guarantee. See options here on Amazon


I couldn’t find out much about this company.  Their products are only sold on Amazon.  They have a 100% Merino wool base layer thermal sets which is  affordable. See options here on Amazon


Engel is a progressive company based out of Germany.  Their products are actually made in Germany using sustainable practices (they have solar and hydraulic power) and employees are paid a fair wage. Most products carry the Global Organic Textile Standard logo.  Most products are also machine washable. See options here on Amazon


Best Merino Wool Base Layers


Lapasa 100% Merino Wool Thermal Set

  • Midweight (200g/m2)
  • Includes top plus leggings
  • XL and XXL sizes
  • Machine washable
  • Buy here


REI Midweight Tights

REI merino base layer leggings

  • Ultrafine Merino wool
  • 200g
  • Flat seams and crotch gussets
  • Black
  • Machine washable
  • Buy here

EcoAble Lightweight Leggings

  • 70% organic Merino wool, 30% silk
  • Lightweight and fine-knit
  • 7 color options
  • XS to L sizes
  • Hand wash
  • Buy here

Icebreaker 150 Zone Leggings

  • 83% merino wool/12% nylon/5% spandex
  • UPF rating 20
  • Black
  • Flatlock anti-chaff stitching
  • Buy here

Minus33 Franconia 100% Merino Wool Leggings

  • Midweight (230g/m2)
  • Flatlock seams
  • 5 color options
  • XS to XXL sizes
  • Machine washable on delicate
  • Buy here

Long Sleeve Tops

REI 200g Merino Top

REI merino wool base layer top

  • 100% Merino wool
  • 200g midweight
  • Arm gussets
  • Droptail hem for tucking in
  • Flat seams
  • 4 patterns/designs
  • XS to XL sizes
  • Machine washable
  • Buy here

Smartwool Quarter-Zip Top

Smartwool midweight Merino base layer top

  • 100% Merino wool
  • 250g midweight
  • 8″ zipper
  • Machine washable
  • Buy here

Icebreaker Crew Top

  • 100% Merino wool
  • Midweight (200g/m2)
  • Crew neck
  • 4 color options
  • XS to XL sizes
  • Buy here

Tank Tops and Tees:

EcoAble Thermal Tank Top

  • 70% organic Merino wool, 30% silk
  • Lightweight and fine-knit
  • Scoop neck
  • 7 color options
  • XS to L sizes
  • Hand wash
  • Buy here

Bras and Underwear:

Engel Boxer Panties

  • 70% Organic Merino wool, 30% silk
  • 3 color options
  • Hand wash
  • Buy here

Icebreaker Siren Bikini Underwear

  • 83% Merino wool, 12% nylon, 5% spandex
  • Lightweight (180g/m2)
  • XS to XL sizes
  • 16 color options
  • Buy here

Icebreaker Sprite Raceback Sport Bra

  • 83% Merino wool, 21% nylon, 5% spandex
  • Single back strap
  • XS to XL sizes
  • 17 color options
  • No side seams
  • Buy here

Do you  have Merino wool base layers? How do you think it compares to other materials? Let us know in the comments!

Image credit: “Merino Sheep at Greenfield Village” (CC BY-NC-ND 2.0) by Maia C

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