We tested the best merino wool base layers on the market according to price, weight, warmth, and comfort. Read on to see how they performed, which is best for you, and get some buying advice.
Table of Content
Best Merino Wool Base Layers
The best Merino Wool Base Layers are:
- Best Overall Merino Wool Base Layer: SMARTWOOL Merino 150 and 250
- Best Budget Merino Wool Base Layer: MERIWOOL Midweight
- Best Ultralight Merino Wool Base Layer: PATAGONIA Capilene Air
- Best 3-season Merino Wool Base Layer: REI Co-Op Merino 185
- Best Merino Wool Base Layer for Active Sports: OUTDOOR RESEARCH Alpine Onset
The product comparison table below is sortable. Click the arrow in the heading cell to sort the models by preferred spec.
|1. Smartwool Merino 150 and 250||Merino 250 Thermal Crew & Bottoms||17.8 oz (250)||Light - Midweight||100% Merino Wool||$110
|Capilene Air Crew & Bottoms||12.4 oz||Midweight||51% Merino Wool||$139
|3. Meriwool Midweight||Merino 250 Long Sleeves & Bottoms||17.91 oz||Midweight||100% Merino Wool||$59.99 each||9/10|
|4. REI Co-Op Merino 185||Merino 185 Long Sleeves & Bottoms||15.6 oz||Lightweight||100% Merino Wool||$79.95 each||9/10|
|5. Outdoor Research Alpine Onset||Alpine Onset Merino Crew & Bottoms||13.9 oz||Midweight||83% Merino Wool||$89
|6. Icebreaker 200 Oasis||Merino 200 Oasis Long Sleeves Crew & Leggings with Fly||14.65 oz||Lightweight||100% Merino Wool||$105
|7. Minus33 Chocorua (Top only)||Chocorua Crew||9.6 oz||Midweight||100% Merino Wool||$79.99||8/10|
|8. Minus33 Ticonderoga (Top only)||Ticonderoga Crew||8 oz||Lightweight||100% Merino Wool||$74.99||8/10|
|9. Woolx 230 Midweight||Explorer Base Layer Top & Backcountry Leggings||18.1 oz||Midweight||100% Merino Wool||$125 (Top), $120 (Leggings)||8/10|
Best Overall Merino Wool Base Layer
SMARTWOOL Merino 150 and 250
Price: $110 each
✅ Best overall
❌ Slightly more expensive
Smartwool, as its name implies, is focused on producing high-quality merino wool products. One of our favorites is the Merino 250, made from thick wool that performs best as an underlayer in the winter. We found both the top and bottom wool base layers to be super comfy and warm, tied with the Meriwool as the warmest on our list.
Our only gripe with the Smartwool 250 is the weight, running a bit heavier than other base layers we tested. But you get a lot of warmth for the bit of extra weight. Price wise the Smartwool runs average to other wool base layers we tested.
As a bonus, Smartwool is known for its colorful and creative clothing. Smartwool has a 2-year satisfaction guarantee as well. The Smartwool Merino 250 is our pick for the best overall merino wool base layer. For more info read our in-depth review of the Smartwool Merino 250 (top and bottom).
Best Ultralight Merino Wool Base Layer
PATAGONIA Capilene Air
Price: $139 each
Patagonia’s Capilene Air is 51% merino and 49% synthetic, which makes it super stretchy. The textured material and unique weave make it the most breathable base we tested. As with all things Patagonia, they are very conscious of their environmental impact. They abide by the Responsible Wool Standard and use recycled polyester for their synthetic blend.
We like that this almost sweater-like base layer is warm and comfy, just like a sweater. The weight is the lightest we tested at 13.9 ounces per pair, making it our top pick for an ultralight merino wool base layer. As with many pieces of ultralight gear, this comes at a premium price. At $139 for each piece, this is the most expensive base layer we tested.
Best Budget Merino Wool Base Layer
Price: $59.99 each
❌ Less comfortable
Meriwool Midweight stands out for its affordable pricing. At just $59.99 this is the least expensive base layer on our list. And at 250g/m2 of wool insulation, it’s also one of the warmest base layers we tested. The design is no-frills and made of 100% merino wool.
Meriwool tops have a fit that you can wear either as a standalone shirt or a base layer. We found the merino wool can be a bit itchy for some wearers, but after a few washes should soften up. Thanks to the thick layer of wool insulation this is also a heavier, winter-centric base layer. If you’re looking for the best bang for your buck the Meriwool Midweight is our pick for the best budget merino wool base layer.
Best 3-season Merino Wool Base Layer
REI Co-op Merino 185
Price: $79.95 each
✅ Great for 3-season use
❌ Not for winter use
- Total Weight: 15.6 oz (18.2 oz top, 7.4 oz bottoms)
- Insulation Weight: Lightweight
- Material: RWS Merino Wool
- Style: Long Sleeve and Bottoms
We love that the REI Co-op Merino 185 wool base layer hits the sweet spot for 3-season adventurers. It’s insulated enough for brisk fall nights while still being lightweight and packable for warmer summer conditions. In winter, it works for active activities like cross-country skiing, but we’d recommend something heavier for less active use.
We found the base layer to be comfortable with a slightly relaxed fit. You could wear it to an après session at the end of the day without feeling like you are in your underwear. The REI Co-op Merino 185 base layers are made following the Responsible Wool Standard and produced in a Fair Trade factory so you can feel confident about where your base layers are made. If you are looking to check multiple boxes with one base layer, this is the one.
Best Merino Wool Base Layer for Active Sports
OUTDOOR RESEARCH Alpine Onset
Price: $89 each
✅ Great for active sports
❌ Not as warm
- Total Weight: 13.9 oz (7.5 oz crew, 6.4 oz bottoms)
- Insulation Weight: Midweight
- Material: 83% Merino Wool, 12% Nylon, 5% Spandex
- Style: Crew and Bottoms
Outdoor Research Alpine Onset series takes the best of Merino wool and mixes it with nylon and spandex for flexibility and durability. We found the layer fit comfortably - it's not too tight, not too loose, and moves when you move. The nylon and spandex also help to hold the shape of the garment through repeated washings.
We give the Alpine Onset clothing high marks for its breathability, thanks again to the mix of materials. It is a midweight layer suitable for active sports in the winter, short walks in the fall, and sleeping in a wide range of temperatures. The spandex is an excellent touch in activities with lots of movement like climbing or ski touring making this our top pick for a merino wool base layer for active sports.
The Other Noteworthy Models
ICEBREAKER 200 Oasis
Price: $105 each
✅ Sustainably sourced wool
- Total Weight: 14.65 oz (8.82 oz long sleeves crew, 5.83 oz leggings)
- Insulation Weight: Lightweight, 200 g/m²
- Material: 100% Merino Wool
- Style: Crew and Leggings
Icebreaker is one of our favorite brands for sustainable wool base layers. We give them high marks both in the sourcing of their materials and how their clothing is made. We found this merino base layer to be slim-fitting, ideal for hiking and sleeping in colder temperatures. We like that Icebreaker offers the Oasis in a variety of styles including crew tops, zippered tops, and bottoms.
We found good attention to detail with offset shoulder seams to reduce chafing when you are wearing a backpack. It also has a drop tail hem that prevents the shirt from riding up and exposing your back to the elements. Another favorite is the legless bottom that stops above the boot and won't add any uncomfortable seams around your ankle. It does run slightly more expensive than other models we tested.
Warm and comfortable is how we describe the Minus33 Chocorua baselayer top. Clothing from Minus33 is made from superfine Merino wool that is softer than most merino wool clothing. We like that the Chocorua has a roomy fit that isn't too baggy or too skin-tight.
We found this merino base layer perfect for wearing as a base layer in the winter or night-time camp clothing during the spring and fall. It has a drop-tail hem to keep your back covered and a regular fit that provides plenty of room. We think the Minus33 strikes a great balance between price, and fit, and is 100% merino wool. The downside is weight, it’s the heaviest on our list.
✅ Can be worn off trail
❌ Less warmth
❌ Less comfort
The Minus33 Ticonderoga is a lighter version of the Chocorua, great for 3-season conditions. At 170 g/m2, the Minus33 Ticonderoga is slightly warmer than the more traditional lightweight base layers we tested.
We found it great for spring and fall hiking or to keep warm on chilly summer nights. The Ticonderoga is a regular fit crew-neck that fits a little looser and looks less long underwear-like and can be worn off trail. If you want a tighter fit consider sizing down. At $79.95 we think this is a good inexpensive piece of merino wool. However, it’s 100% merino wool and can be a little itchy at first.
Woolx 230 Midweight
Price: $125 (Top), $120 (Leggings)
✅ Super comfy
The Woolx 230 midweight uses exceptionally soft merino making it the coziest base layer on our list. We found it didn’t itch and felt as soft as cashmere. We like the simple design and slim athletic fit making it comfortable for all activities.
It's made with non-chafing flatlock seams and cuffs to keep pants and sleeves from riding up. It looks and feels like a classic piece of long underwear and we wouldn’t want to wear this layer outside of camp. The downside is that this is the second heaviest and most expensive on our list.
Key Factors to Consider When Choosing
Wool comes at a premium cost compared to synthetic materials. The thicker (i.e. warmer) a wool base layer is, the higher the cost. Extra design features like hoods, zips, and technical blends of materials can also add to the cost.
Merino wool base layer that provides the greatest value:
Affordable merino wool base layer:
Premium merino wool base layer (most expensive):
Merino wool offers the best warmth-to-weight ratio of any fabric. When comparing weights of merino wool base layers look at the insulation weight, i.e. fabric density, which is measured in g/m2. The higher the number, the heavier (and warmer) a fabric is. The style of the base layer, i.e. Short sleeved, vs. long-sleeved, also affects weight.
The Lightest merino wool base layer:
Most merino wool garments are categorized by the number of grams of merino wool in every square meter of fabric. The higher the number, the warmer the garment. Merino wool base layers are classed as ultralight, lightweight, midweight, or heavyweight.
- Ultralight (less than 150 g/m2): A great option when you're hiking in the heat. It will help you keep both sweat and odors to a strict minimum while also shielding your skin from the sun.
- Lightweight (between 160 and 190 g/m2): Lightweight merino wool base layers can be worn all year round.
- Midweight (between 195 and 250 g/m2): You’ll want a midweight merino layer for the cold winter months. It's a perfect base layer for snowshoeing and skiing.
- Heavyweight (greater than 250 g/m2): These dense layers are great for ice fishing, hunting, or other similar low-key activities. A heavyweight merino wool base layer may be too warm for strenuous activities such as hiking or climbing.
The warmest merino wool base layer:
Your merino wool base layer will be against your skin, making comfort a top priority. Look for a base layer that fits snugly but not so tight that it’s compressing you. Avoid going too baggy. A baggy base layer won’t effectively wick moisture away from your skin.
Some merino wool base layers mix in synthetic materials to give extra stretchiness and a smoother feel to your skin. Features like a zippered top or ¾ length sleeves or bottoms can help to regulate temperature, keeping you comfortable when the conditions change.
The most comfortable merino wool base layer:
Other Things to Consider
As a base layer, usually, the fabric encounters less wear and tear than other items. Still, you want your merino wool base layer to last as long as possible. 100% merino wool base layers are less durable than those with a synthetic material blended in. The more synthetics, the better the durability becomes. However, if too much synthetics are blended in, you start to lose the benefits of merino wool.
Base layers do their magic by managing moisture and keeping your body temp regulated. To do this, they must fit properly. Too baggy and it won’t effectively wick moisture away, too tight and it will feel constrictive. An ideal fit is nice and snug but not too tight where it’s compressing you.
Every company is going to have its own unique fit and style. For example, the REI Co-op Merino 185 and Patagonia Capilene Air are both going to have more of a sweater fit, while the Arc’teryx Rho LT and WoolX 230 are both more of a trim performance fit.
From 100% merino garments to synthetic blends, the material being used is going to perform differently based on the ingredients. Merino fibers offer the highest weight-to-warmth ratio but are more delicate than synthetic fibers. While synthetic fibers are stronger and stretchier.
The most common synthetic fibers being nylon, spandex, and polyester. Nylon is added for strength/durability, spandex is added for stretch, and polyester is added for quicker drying.
A lot of base layers now use a blend of merino and synthetic fibers, with the best blends using a core-spun fiber. The wool is wrapped around synthetic fibers, so the merino is against your skin but has a stronger synthetic core.
Keep an eye on the proportions too, you will start to lose the advantages of merino as you get down below 80%. Different activities are going to be better suited to different materials.
If you are climbing, a higher amount of synthetic fibers will help keep the shirt from wearing out too fast. If you are skiing or using it when sleeping, it’s not going to see the same kind of wear and tear so 100% merino is the best.
A close-up of the inside labels of Patagonia Capilene Air and Minus 33 crew.
It has become increasingly important to ensure that the merino wool of your base layer has been sustainably sourced. You can do this by purchasing from brands that ensure that no animal cruelty has occurred in the sourcing of their merino wool.
Some brands have had their merino wool certified as sustainably and ethically sourced. Some certifications to look out for are ZQ Merino Standard, Global Organic Textile Standard (GOTS), and The Responsible Wool Standard. Some brands will also source their wool from countries like Australia and New Zealand that have strict laws on wool sourcing.
Merino wool is naturally resistant to odor-causing bacteria thanks to its ability to manage moisture. Without moisture, odor-causing bacteria cannot multiply and cause your wool shirt to stink.
Because of its odor-control properties, merino wool clothing doesn't need to be washed as frequently as cotton or synthetic fabrics. When hiking, I can wear merino wool socks for up to a week and t-shirts for three days before washing.
Merino wool has odor-control properties and can manage moisture preventing your shirt from stinking.
Merino wool fibers are among the most breathable and moisture-wicking fabrics available. Each strand can absorb up to 30 percent of its weight in moisture; wicking it away from your skin and out towards your surrounding environment. As a result, the fabrics feel cool and dry against your skin even when you are sweating up a storm.
Merino wool naturally protects your skin from the sun's damaging rays. Most wool clothing has a UPF rating of 30+ or higher.
Merino wool is inherently quick dry without any treatment or coatings. It dries so quickly because it doesn’t absorb water the way other materials do. Unlike cotton which can absorb over 25 times its own weight, merino wool absorbs less than half of its own weight. Meaning, there is a lot less water to dry. Having dry clothing is critical and we can’t always escape getting wet, so having a base layer that will rapidly dry is essential.
Base layers must fit properly to effectively wick moisture away.
What are the benefits of merino wool?
The main benefits of merino wool are odor resistance, breathability, quick drying, UV protection, and lightweight material.
- ODOR RESISTANCE: Merino wool is naturally resistant to odor-causing bacteria thanks to its ability to manage moisture. Because of this, it doesn’t need to be washed as often as other fabrics, another great benefit of merino wool.
- BREATHABILITY: Merino wool fibers are among the most breathable and moisture-wicking fabrics available. Each strand can absorb up to 30 percent of its weight in moisture; wicking it away from your skin and out toward your surrounding environment. As a result, the fabrics feel cool and dry against your skin even when you are sweating up a storm.
- UV PROTECTION: Merino wool naturally protects your skin from the sun's damaging rays. Most wool clothing has a UPF rating of 30+ or higher.
- QUICK DRY: Merino wool is inherently quick dry without any treatment or coatings. It dries quickly because it doesn’t absorb water the way other materials do. Unlike cotton which can absorb over 25 times its own weight, merino wool absorbs less than half of its own weight. Meaning, there is a lot less water to dry. Having dry clothing is critical and we can’t always escape getting wet, so having a base layer that will rapidly dry is essential.
- LIGHTWEIGHT: Not all fibers are created equal. Merino wool offers the best warmth-to-weight ratio. Compared with other fibers and materials of the same weight, merino is simply warmer. This means you can have a much thinner, lighter garment and won’t have that bulky feeling when you have multiple layers on.
Is merino wool good for a base layer?
Yes, merino wool is good for a base layer because of its high performance in all conditions. Merino wool offers superior odor resistance, high breathability, is lightweight, quick-drying, and comes with natural UV protection. It’s very comfortable as well.
📸 Some photos in this post were taken by Ross Enlow (@rossaenlow)