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SmartWool Merino 250 Bottoms Review

An extremely warm and breathable pair of bottoms built to keep you warm in the coldest conditions but versatile enough to carry into seasons outside of winter.
Top Pick Award
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Price:  $95 List | $71.21 at MooseJaw
Compare prices at 3 resellers
Pros:  Extremely warm, super cozy, terrific temp regulation, breathable
Cons:  Stretches out, soggy crotch, slow to dry, expensive
Manufacturer:   Smartwool
By Roland Mott ⋅ Review Editor  ⋅  Dec 20, 2018
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#3 of 8
  • Warmth - 30% 9
  • Breathability - 30% 7
  • Comfort and Fit - 30% 6
  • Durability - 10% 8

Our Verdict

The super cush and thick merino wool is meant to keep you warm in the coldest climates. THe SmartWool Merino 250 Bottoms are perfect for those adventuring into the deep recesses of winter or people working in really cold conditions. The 100% merino fabric insulates like a furnace but breathes wonderfully making this layer really versatile; performing in super cold conditions but not forcing you to overheat when you get into warmer situations. A workhorse bottom this kept us warming skinning ridgelines and ice climbing alike.

If you're looking for a similar level of warmth in a bottom that is going to be more durable, we suggest looking into the synthetic Arc'teryx RHO LT bottoms. For a versatile merino bottom that is going to breathe just as well but not be quite so toasty, the SmartWool Merino 150 is a terrific lighter weight option. All in all, we love the warmth to versatility ratio of the SmartWool Merino 250. Read on for more details on this terrific base layer.

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Our testers are big fans of the SmartWool Merino 250 top, which won our Editors' Choice Award in our base layer tops review.

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Our Analysis and Test Results

Our Top Pick for Warmth, the SmartWool Merino 250 balances insulation for really cold climates with comfort and breathability that make it at home in a sideways snow-blowing blizzard and for a day of reading and movies lounging around the cabin.

Performance Comparison

The ultra cush  thick and cozy fabric of the 100% merino 250
The ultra cush, thick and cozy fabric of the 100% merino 250


Boasting 250g of thick and cozy 100% merino wool, these bottoms are constructed to excel in harsh conditions. They do a superb job of wicking away sweat when you're working hard and drying quickly against your skin so that after skinning endlessly for the perfect line, you're not soaked and freezing when you finally reach the windblown and frozen summit.

The naturally hydrophobic fibers of merino wool resist absorbing sweat which allows for warmth and comfort throughout a full day of varying intensity of activities and temperatures. These bottoms were glued to our burning thighs on the 6,000 vertical feet of skinning and climbing to reach the summit of Mt. Hood in the heart of winter. From frigid, windy pre-dawn temps to the double-digit afternoon and into the cold dark night these bottoms kept us warm, dry, and happy the whole time! They are warm but not expedition weight warm, if you're heading to the coldest regions on earth, you will need something thicker. The other pair of bottoms that are comparable in warmth are the Arc'teryx RHO LT, which we also absolutely love.

Nearing the summit of Hood.
Nearing the summit of Hood.


What makes these bottoms so impressive beyond their comfort is their ability to provide such incredible insulation while maintaining a healthy ability to breathe. This combination is not easy to find. A lot of times a thick and warm fabric will do great in cold situations but once you start working hard they will cause you to overheat and will hold onto sweat, becoming clammy and lending itself to cold once you stop moving. The merino wool naturally wants to repel water and does an excellent job at wicking sweat away from the skin and using the pressure/temp variance between your skin and the air to dry quickly so you're not left with clammy or sweat soaked bottoms.

The uncanny ability of merino, and these bottoms specifically, to deliver maximum heat as well as maximum breathability is like striking gold! Although its breathability is impressive for its weight and warmth, it is not going to breathe as well or efficiently as it's thinner partners. A lighter weight merino layer like the SmartWool Merino 150 or the Outdoor Research Alpine Onset are going to be far superior at breathability but not provide as high a level of warmth.

Seeing how our thickest pair of bottoms does when the sun warms things up a bit on a fall river trip.
Seeing how our thickest pair of bottoms does when the sun warms things up a bit on a fall river trip.

These bottoms and all merino wool fibers need to be forced to absorb water. Wool is naturally hydrophobic and so it takes quite a bit of effort to soak them thru. Once they are soaked thru, they are heavy and slow to dry. Situations where you are wearing longies that are soaked all the way through are hopefully rare unless you're accustomed to jumping into lakes with your long johns on. In the drying test, these were the slowest to dry, and not surprisingly as they are the thickest bottoms we tested.

Nearing the end of the skinning slog and getting excited to put on crampons! Mt. Hood  OR
Nearing the end of the skinning slog and getting excited to put on crampons! Mt. Hood, OR

Comfort & Fit

These bottoms are heavenly when it comes to comfort. SmartWool's 250 weight merino has won over the hearts of everyone here at OutdoorGearLab. The fabric is thick, soft, incredibly stretchy, and super warm. We don this fabric the Cadillac of Cush. When it comes to comfort, these bottoms are the creme de la creme and second to none! They fit snug against the skin but are not itchy at all. The stretchy fabric allows the ankle of the pant to slide over the heel easily and fits both thick and thin legs well. Even though they are made of a thick fabric, they layer well under ski pants and jeans alike.

Here's the fit of the Merino 250 bottoms on our 6' lead tester.
Here's the fit of the Merino 250 bottoms on our 6' lead tester.

A minimalistic seam design allows for a single seam to run the length of the leg on the inseam instead of two. Flatlock seams sit comfortably against the skin and a gusseted crotch allows for unrestricted mobility. The waistband deserves its own review! It is by far the most comfortable waistband we tested. The waistband is not a separate material from the pant, it is a seamless continuation of the bottom. The same comfortable merino on a flat and wideband that lays comfortably on the waist. The only room for improvement that we observed is in the crotch. When worn at a respectable place on the waist, there is a bit of crotch sag. For the crotch to fit correctly we found that we had to hike them up just beyond our belly button. The Arc'teryx RHO LT offers similar warmth in a synthetic package but has a phenomenal fit and equally as comfortable fabric next to the skin.

The uber-comfy waistband of the SmartWool Merino 250
The uber-comfy waistband of the SmartWool Merino 250


Being the thickest merino layer, these are easily the most durable among the merino layers we tested. Nearly all of the merino bottoms developed a hole during our abrasion test whereas these boasted mere surface wear. As they are merino they are just simply not as durable as a synthetic fabric but they offer the breathability, wicking capabilities, and non-stink that only merino can promise.

The soft material can tear easily if it is snagged on sharp edges and develops holes in high use areas after extended use and abuse. As with all merino, washing and especially drying dramatically decreases the life of a merino garment. We suggest washing these only when you need to and laying them flat to dry. All that said, of the merino options on the market, these are the most durable but are still not going to hold up to synthetic competitors like the Arc'teryx RHO LT.

Tough like the summit winds  the thick fabric of the SmartWool Merino 250 is by far the most durable merino bottom we tested.
Tough like the summit winds, the thick fabric of the SmartWool Merino 250 is by far the most durable merino bottom we tested.

Best Applications

Excelling in warmth, breathability, and body temperature regulation, these bottoms are best used for situations that range from cool weather to downright nasty cold. These are a great do-it-all bottom for people that need a base layer that can perform in a lot of situations including extreme cold. Because they are thick and warm we suggest them for low to moderate activity levels in cool to cold weather.

Single digit temps and a white out  perfect conditions for the SmartWool Merino 250 bottoms!
Single digit temps and a white out, perfect conditions for the SmartWool Merino 250 bottoms!


At $95 this is the most expensive pair of bottoms in our review but we feel like the quality and versatility of the product warrants the price. All merino layers are expensive and the other top performing layers in the review are only slightly less money. The most affordable merino layer is the Icebreaker Everyday Leggings at $70 but is not as warm or durable as the SmartWool 250.


All in all, the SmartWool Merino 250 bottoms offer a great balance of warmth and breathability in an ultra-comfortable package. They are a great investment for those needing a pair of bottoms for very cold weather but wanting a layer that isn't stuck working in only freezing conditions.

Roland Mott