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Smartwool PhD Pro Free Ski Review

Our favorite ultralightweight ski and snowboard sock
Smartwool PhD Pro Free Ski
Credit: Smartwool
Top Pick Award
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Price:  $31 List
Pros:  Very breathable, fantastic wicking power, thoughtful cushioning, compressive fit
Cons:  Not as durable, not very warm
Manufacturer:   Smartwool
By Amber King ⋅ Senior Review Editor  ⋅  Dec 19, 2019
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  • Comfort & Construction - 25% 7.0
  • Warmth - 25% 6.0
  • Breathability - 25% 10.0
  • Fit - 15% 9.0
  • Durability - 10% 6.0

Our Verdict

If you hit the slopes hard, the Smartwool PhD Pro Free Ski sock is meant for you. This ultralight sock is a favorite for its wicking power that keeps feet dry when transitioning from the moguls to the ski lift. The sock doesn't offer much in the form of insulation, but it is still quite warm because it'll keep your feet dry. While it's not the most durable option out there, it offers the best breathability and thoughtful construction we've seen in a while. If you have super tight boots and want a ski sock that wicks with sufficient protection, this is the one to buy. Our backcountry touring-testers also loved this sock for earning their turns. Be aware that if you don't charge hard, you'll be better off with a thicker, warmer pair of socks.

Our Analysis and Test Results

Our favorite ultralightweight sock. It offers the best wicking power and breathability of any sock tested. Strategically placed cushioning in the shin is also breathable with a little extra in the heel. If you own a pair of super-tight ski boots and you want a sock that'll wick away moisture without adding additional insulation, this merino-synthetic wool sock is our favorite.

Performance Comparison

Smartwool PhD Pro Free Ski ski socks - ski tour or enjoy the resort in these ultra-breathable socks. they...
Ski tour or enjoy the resort in these ultra-breathable socks. They are fit for all types of weather, depending on the insulation in your boot. What's clear is the thin design won't compromise the fit of your boot, offering good performance and comfort for all-day play.
Credit: Amber King

Comfort & Construction

This is a bare-bones sock with cushioning in all the right places. We wore this sock while skiing, snowboarding, and hiking and thought it was comfortable for all-day wear despite its thin design. The ultralight design is the thinnest of any of the socks we've tested. Though, the merino wool construction feels comfortable against the skin.

Underfoot, there is little to no cushioning, except for a tiny bit in the heel, but none at the top of the toes. Throughout its length is a series of compression paneling for a super tight fit. The calf has thinner material that offers just a little cushioning in the shin. The block of cushioning is latticed with breaks in the fabric for areas of more ventilation. This sock does an impeccable job of putting cushioning in the places that it is needed, without too much or too little. It provides protection from shin bang and impacts from hitting kickers or moguls at the resort and in the backcountry.

Smartwool PhD Pro Free Ski ski socks - thin with a little cushioning in the heel, shown here worn...
Thin with a little cushioning in the heel, shown here worn inside-out for better visibility.
Credit: Amber King

Smartwool PhD Pro Free Ski ski socks - the padding on the shin is minimal but offers all the right...
The padding on the shin is minimal but offers all the right protection you need. Its high density with breathable vents throughout. Sock shown here is worn inside-out for the sake of detail!
Credit: Amber King


The ultralight construction makes it less insulative than any of the socks tested. However, it has amazing breathability and wicking power (which we'll discuss later) while it means that moisture doesn't get caught in the fabric. This inherently leads to more active warmth when skinning uphill or going hard at the resort. This sock is for those that simply need a wicking layer without bulky insulation. If you need a warmer sock, this is not a good option. But if you prefer thinner construction, it's our top recommendation.

When testing, we encountered both warm and cold days on the hill. When hiking and skiing in super cold weather, we were surprised at how warm our feet felt while we moved over the terrain. When skinning up in the backcountry, this sock removes moisture from the foot. When we stopped to transition, we still felt warm, despite the thinner construction. If you rely on the insulation of your boot for warmth, then this sock will work. However, if your boots aren't very warm and you need a thicker sock, it's not a great option. Its warmth comes in the form of its ability to keep your feet dry in both dry and wet conditions.

Smartwool PhD Pro Free Ski ski socks - this sock offers great warmth when in motion and while standing...
This sock offers great warmth when in motion and while standing still despite its thinner construction. It's awesome breathability will keep feet dry while your boot insulates.
Credit: Amber King


Breathable with huge wicking power. It has thinner construction throughout, with padding only where it's needed. The merino wool construction allows moisture transfer to be efficient, keeping your feet dry even on the sweatiest days of the winter. What's more, in high sweat zones, the fabrics are built to include larger loops, increasing the surface area to wick away moisture. The 41% nylon does well to wick away sweat and dry quickly. Of all the socks tested, it is the most breathable, earning it a Top Pick. If you have sweaty feet or prefer a thin sock, you can't go wrong with the PhD Pro.

On a super warm day in the backcountry, we wore a thicker sock next to this thinner option. We noticed that our feet were much drier in this sock than the thicker sock that had more insulation at the bottom of the sock. Even when temperatures rose above freezing, and the sun streamed down, our feet stayed dry. We appreciate the thinner construction of these socks to keep feet dry when going from in motion to standing still.

Smartwool PhD Pro Free Ski ski socks - thin materials and thoughtful padding make this the most breathable...
Thin materials and thoughtful padding make this the most breathable sock tested. It also has long loops of fabric in high sweat zones to help promote wicking ability.
Credit: Amber King


This sock doesn't have a specific left or right fit. Our testers, both skiers and snowboarders, felt that it was specific and didn't bunch in any odd areas, despite the lack of specificity.

The material is quite stretchy and offers sufficient height to protect for both skiers and snowboarders alike. It features compression panels around both the ankle, arch, and upper calf to ensure that the sock stays in place. Since it's not loaded with insulation, the sock stays stuck to the foot and doesn't move. This is why it's so great at wicking and breathing. We had both male and female testers try it out, and they both thought it worked. The fit feels tight and compressive, but the elastic cuffs aren't limiting, working for those with thin and thick, athletic calves.

Fit with boots from the front.
Fit with boots from the front.
From the side.
From the side.
Smartwool PhD Pro Free Ski ski socks - this sock offers a tight and specific fit that doesn't compromise...
This sock offers a tight and specific fit that doesn't compromise the fit of your ski boot.
Credit: Amber King

This sock also comes in a women's specific fit.


With a thinner construction, this is a less durable sock than thicker options or those built by Darn Tough. After 60 hours of use while hiking, skiing, and snowboarding, we've seen some pilling in high wear areas. Others built with synthetic materials, or those that are thicker, don't show this break-down. That said, for the impact, we've put it through, it's still doing pretty good. It hasn't compacted nor has it's level of performance deteriorated in our testing period.

This sock comes with a 2-year warranty and is built with the PhD fabric offered by Smartwool. Of all the merino wool options with this company, it is the strongest. While it hasn't shown to offer the same durability as Darn Tough options, it still does a great job. Expect it to last you a few seasons.

Smartwool PhD Pro Free Ski ski socks - here we see a little bit of pilling after 60 hours of use, but other...
Here we see a little bit of pilling after 60 hours of use, but other than that, it's a well-constructed ski sock that'll last you for many seaons.
Credit: Amber King


This sock is pretty expensive for the price. It does come with a 2-year warranty, but there are other more durable lightweight options out there. That said, this sock offers just a little more cushioning in the heel than other lightweight contenders and better overall breathability. If the thinnest sock is what you seek, you might be up to spending the money on this sock. However, if you want to pay a little less and get a little more longevity from your ski sock, there are better options out there.

Smartwool PhD Pro Free Ski ski socks - a look at our favorite sock for its breathable construction.
A look at our favorite sock for its breathable construction.
Credit: Amber King


The Smartwool PhD Pro Free Ski is built for those that seek ultralightweight construction. This sock offers minimal padding, only where it's needed, and does best at wicking away moisture and breathing well. If you prefer a sock that simply works as a wicking layer, without additional insulation, this is our favorite option. This sock is built for tight-fitting boots with a little extra cushioning in the shins for higher impacts on the ski hill.

Amber King

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