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It’s just not a sock for the sedentary, that’s for sure. The Smartwool PhD Outdoor Medium Crew works only as hard as you do to keep warm. It’s light cushioned with medium thickness, meaning its designed for activity. In the field, the PhD wicks moisture, regulates temperature and keeps you cozy all day.

Trail running in the Smartwool PhD Outdoor Medium Crew hiking socks
Trail running in the Smartwool PhD Outdoor Medium Crew hiking socks

We tested and reviewed the Smartwool PhD hiking sock alongside five other top competitors. It’s a great option to be sure, but if you’re looking for greater durability or a sleep time sock, the two best words are Darn Tough.

If you’d like to read more about how the Smartwool PhD Outdoor Medium Crew compared to the other hiking socks we tested, check out our article on the best hiking socks. Or, continue reading for our full review.

Hiking Socks Score Material Fabric Thickness Cushion
Runner-Up: Smartwool PhD Outdoor Medium Crew (This Product)
62% Merino Wool, 36% Nylon, 2% Elastane Medium Light
Top Pick: Darn Tough Light Hiker Micro Crew Light Cushion
47% Merino Wool, 46% Nylon, 7% Lycra Spandex Medium Very Light
Darn Tough Hiker Micro Crew Cushion
67% Merino Wool/29% nylon/4% Lycra Spandex Medium Light
Best Value: Wigwam Hiking Outdoor Pro
40% Olefin, 36% X20 Acrylic, 20% Stretch Nylon, 4% Spandex Medium Midweight

What We Like

Merino wool is a renowned moisture-regulating fabric, meaning that though you will sweat in a Smartwool sock, rarely ever will you drench them. Especially during high activity, the Smartwool PhD socks are comfortable, soft, and generally warm enough, but not excessively padded.

Moisture Control

Breathability is the name of the game for the Smartwool PhD. Unmatched moisture management means your feet won’t get wet or soggy, which equates to lower likelihood of developing blisters or chills. The PhD is made up of 62% merino wool, meaning the moisture-wicking abilities are excellent.

As recognized by Smartwool, “both synthetics and wool have the ability to wick, but only wool has the ability to wick away moisture in its vapor state.” It keeps up with you.


I’ve found that hiking socks with overly thick cushioning cause more blisters and unnecessary rubbing. Light cushioned socks, by contrast, dry quicker and still provide all the comfort and warmth you need. And when you’re talking about merino, you’re talking about the softest fabric on the market. No itch, ever. The Smartwool PhD has the perfect amount of cushioning for high activity.

Research suggests that shoes that offer too much cushion can be bad for your foot. “Cushioning lulls you into thinking you can slam your foot down,” says Dr. Irene Davis. Likewise, too much cushioning in a sock can create the same false sense of security and affect how you hike.

An extreme example: Over the summer, I sprained my ankle, bad. However, I had a 7-day backpacking trip in Colorado’s Weminuche Wilderness planned in a few weeks.

Not to be deterred by injury, I went on the hiking trip, with a very thick, cushioned (admittedly too large) ankle brace under my sock.

It completely changed my walking form, so much so that the plantar fasciitis symptoms (not the ankle problem) were crippling by the end of day one. Day two, I opted out of the brace and everything was fine.

Will a thick hiking sock cause you crippling pain? Doubtful. However I appreciate the very thin cushion of the PhD for hiking activities.


The Smartwool PhD is a great sock for pretty much any daily activity, especially hiking, because it breathes. Unless skiing in fierce winter conditions, I’d comfortably take the PhD pretty much anywhere. Merino wool works as hard as you do. It’s able to hold up to 30% of its weight in moisture and still feel dry to the touch.

What We Don’t Like

Merino wool dries slower than other synthetic fabrics, meaning that you’ll often experience cold toes. Also, this particular sock is not great for sleeping or lounging.

Slipping my feet out of my insulated XtraTuffs on a 20 degree day. Cold.

Cold Toes

The PhD is less likely to get wet, but when it does, it stays wet. After a long day of hiking, your toes will stay warm as long as you keep your insulated boots on. After that, you can forget about warming yourself up at camp. There is a reason we separate the hiking socks from the camp socks. When you are not actively warming yourself up through physical exertion, neither are the socks.


Have you ever took a big old whiff of a wet sheep after a rain?

If not, you can at least imagine it by snorting a pair of hiking socks after a three-day trip. Merino is supposedly much less odorized than other wool. That doesn’t mean you can’t knock out a hound dog with your eau de locker room perfume.


As a rule, don’t sleep in the same socks you hiked in. Still, I’d never designate these socks just for sleeping because I naturally run very cold at night and the medium-fabric thickness isn’t what I want during the winter months.

This is more personal preference, but if you frequently get cold, you should go with something thicker.

Best Uses

The Smartwool PhD is best used for hiking, trail running and maybe even spring cross country or downhill skiing. I would never sleep in these socks because they are not thick enough.

Because of the fun designs and patterns that make these quintessential Smartwool, I wear them to work too. They are lifestyle socks.


The Smartwool PhD has a higher price point than similar products. So, what are you gaining?

Cool colors and patterns, versatility and the reliability of the tried-and-tested Smartwool brand.

Still, the long term durability does not compete with it’s competitor Darn Tough, which can be found for cheaper basically anywhere. However, I have found plenty of Smartwool socks on sale (I got my first pair on sale at an Ice Climbing expo when I renewed my Leave No Trace Membership).

I like Smartwool overall, but I really love the cheaper Darn Tough that does most everything better. If you have a pair of Smartwool, don’t feel bad about it, but consider an upgrade next time.

How the Smartwool PhD Outdoor Performed in Our Testing

Hike Test

No rubbing, no blisters, no tugging or itching.

The Smartwool PhD socks shine in a hike test, where your body is consistently working at a steady pace. As I’ve said, the Smartwool socks work only as hard as you do. Anyone who sweats a moderate amount during moderate exertion will keep their feet dry for the majority of a day. It’s when you stop that everything catches up with you.

Sleep Test

Sleeping in the PhD Outdoor socks is a cold affair, whether you’re in your bed at home or in a sleeping bag resting your head on your favorite backpacking pillow. For sleep socks, I recommend packing a separate pair just for sleeping — and considering a different thickness or brand entirely.

Fitness Test

You sweat while you hike. But you really drench yourself, say, climbing stairs. As part of our review, we wore these socks on a stair running workout during winter in Colorado. Our toes stayed warm through the entire activity. No blisters, no rubbing and no stretching.

However, when I took my shoes off after returning home, all chill broke loose. The PhD sock manages moisture well in practice, but not so much sitting still.

Product Specs

  • Material: 62% Merino Wool, 36% Nylon, 2% Elastane
  • Thickness: Medium
  • Cushion: Light

The Bottom Line

After a full day of hiking, your socks will be damp, especially towards the toes. However, the Smartwool PhD Outdoor is a versatile activity sock that manages moisture, maintains warmth and keeps it shape under rigorous conditions. It’s when you slow down that this sock starts to lose its best qualities.

With any thin- to medium-weight sock, you must generate your own heat. You can’t expect the sock to keep you warm, say, during sleep. When backpacking with the Smartwool PhD, you’re going to want to designate a different, perhaps thicker sock for camp activities and bedtime.

If you’re looking for more durability and reliability long term, the Darn Tough Light Hiker is a good route.


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