Reviews You Can Rely On

Smartwool PhD Ultra Light - Women's Review

The PhD Ultra Light is a lightweight, comfy shirt great for any adventure
smartwool phd ultra light for women running shirt review
Smartwool PhD Ultra Light
Credit: Smartwool
Price:  $70 List
Manufacturer:   Smartwool
By Lauren DeLaunay ⋅ Senior Review Editor  ⋅  Jul 31, 2018
  • Comfort - 30% 8.0
  • Breathability - 30% 7.0
  • Drying Time - 20% 7.0
  • Features & Versatility - 20% 7.0

Our Verdict

As one of the only non-synthetic shirts that we tested for this review, the Smartwool PhD Ultra Light immediately stood out. Our testers wondered if a wool top could provide the same protection and comfort as the wool socks that we adopted long ago. We spent weeks in this shirt, running, biking, hiking, and climbing-- doing pretty much anything to work up a sweat. What we found was an amazingly soft, very breathable shirt that was just as suited to the mountains as it is to the track. We couldn't find a place to not bring the PhD Ultra Light, which led us to our big decision: our team was psyched to award this shirt our Top Pick for Versatility. Though a little pricey, we think this product is an incredible investment no matter what sweat-inducing activity you're embarking on.
Slower to dry

Our Analysis and Test Results

The Smartwool PhD Ultra Light running top stood out in this review for its high level of comfort and all-around performance. Despite a steep price tag, this top's merino construction make it an excellent partner in the backcountry, and its fit and feel had us wearing it long after the workouts ended. We awarded this shirt our Top Pick for Versatility for those very reasons.

Performance Comparison

smartwool phd ultra light for women running shirt review - the phd ultra light is comfortable, breathable, and extremely...
The PhD Ultra Light is comfortable, breathable, and extremely well-rounded.
Credit: Lauren DeLaunay


Comfort is a giant category, as there are so many factors that contribute to the overall fit and feel of a shirt. It's also a bit subjective, so we tried to rope our friends and colleagues into our testing as much as possible to help us reach a consensus. The PhD Ultra Light has a very different feel than its competitors, but we couldn't help but adore it.

The main bodice of this shirt is made of 56% merino wool and 44% polyester, while the "mesh" under the sleeves has a bit more airflow, with a merino-to-polyester ratio of 54% to 46%. We found the material to be incredibly soft and cozy, and it quickly became one of our favorite base layers for nearly every activity. Whether we were biking to the supermarket or out for a day of rock climbing, the PhD was a no-brainer.

smartwool phd ultra light for women running shirt review - checking out a close-up of the phd ultra light's mesh underarm panels
Checking out a close-up of the PhD Ultra Light's mesh underarm panels
Credit: Lauren DeLaunay

The seams, while flat-lock, are a bit more noticeable than the taped seams of the Patagonia Windchaser, which is one of the reasons we found the Windchaser to be a bit more perfectly suited for running specifically. We did appreciate, however, that the seams were removed from the top of the shoulder which helps prevent rubbing when wearing a pack or running vest.

While the Windchaser and Nike Tailwind had a more athletic, looser fit, our testers generally liked the more tapered cut of the PhD. The seams cut across the sides for a more feminine fit, and the sleeves are narrow without being constricting. This shirt is definitely stretchier than the Windchaser and is on par for range of motion as The North Face Reaxion Amp, our Best Buy Award winner.


When we first tried on the PhD Ultra Light, we were pretty surprised at how light it felt. In order to test its breathability, we hit the trails and didn't stop until we worked up a sweat. While drying time, described in more detail below, tells us how quickly a shirt dries out once it's saturated in moisture, this scoring metric was used to tell us how well a shirt prevented saturation in the first place.

And while drying time is easier to test in a controlled experiment, we had to do some finagling to find a more objective way to test breathability. So what did we do? We went out with multiple shirts and changed mid-run or mid-hike. We wanted to see how these products did in a direct side-by-side comparison, so we needed to use them in similar conditions. We traveled all over Argentina and California in these shirts in a wide variety of temperatures and climates, but no matter where we were, we were impressed with the PhD's ability to keep us dry.

smartwool phd ultra light for women running shirt review - the phd ultra light is both soft and performance-driven.
The PhD Ultra Light is both soft and performance-driven.
Credit: Lauren DeLaunay

The mesh-like underarm panels did a fantastic job at allowing airflow, and the bodice was great as well. Whether we were hiking with a pack or running on the track, the PhD Ultra Light felt amazingly dry.

Drying Speed

When we set out to discover which shirt was the best running shirt on the market, we quickly learned that there were two different characteristics that kept us feeling dry. Breathability, which we describe above, measures airflow and the product's ability to stay dry despite a lot of moisture. Drying time, which we explain here, measures the ability of the product to dry out quickly once saturated. To measure this, we did a controlled experiment.

After dunking each shirt in water, getting them fully saturated, we wrung them out quickly by hand and hung them up to dry side-by-side. The PhD, as we had suspected, was moderately quick to dry. It was much slower than the Patagonia Windchaser, our Editors' Choice Award winner, and fell right about in the middle, behind two other synthetic products, the Brooks Distance and Arc'teryx Taema.

Drying time is important despite the PhD's great breathability because evaporation helps keep us cool. While we would have liked to see a faster drying time on this shirt, we're a little more confident in its abilities because of its sufficient breathability.

Features & Versatility

There were a few other traits we wanted to reward in this category, but since they were so small, we decided to lump them all together. For this metric, we decided to look at features that make something specifically suited to running, like pockets and sun protection, as well as the product's ability to be used for other activities.

The PhD Ultra Light has a small reflective logo on the front of the shirt, but nothing on the back, something many of its competitors did sport. While not specifically treated for odor control, wool is much more naturally odor-free than synthetic materials, a quality we really appreciated in this product. Our testers also would have liked to see some sun protection built in, something that only two shirts, the Taema and Marmot All-Around, had.

smartwool phd ultra light for women running shirt review - while lacking in extra features, the phd ultra light has flatlock...
While lacking in extra features, the PhD Ultra Light has flatlock seams and a merino construction that make it super versatile.
Credit: Lauren DeLaunay

As far as versatility goes, this is where the PhD Ultra Light shines. Because of wool's breathable, odor-resistant construction, we found this shirt to be an incredible base layer for just about any activity. As mentioned above, this shirt has amazing range of motion and comfort, two things that brought us back to it time and time again. While the features were definitely lacking, this shirt's excellent versatility is what gave it a high mark in this category.

Best Applications

As we touched on above, our favorite thing about the Smartwool PhD Ultra Light is how well suited it is for just about any adventure. The wool is perfect for the whole range of temperatures you might find yourself in, and we'd be equally psyched to wear this shirt on a hot summer bike ride as a cold backcountry ski tour. The odor-free nature of wool combined with this shirt's superior comfort helped it stand out as one of our favorites, which is why we were so excited to award it our Top Pick for Versatility.


Coming in at $70, this is not a cheap shirt. Up there with the most expensive products in this review, we can't help but squirm at the price tag. That being said, our testers generally felt that the incredible versatility of this product makes it a great investment piece and one you can use and abuse day in and day out. That being said, the overall performance just isn't that much better than our Best Buy Award winner, The North Face Reaxion, which we'd recommend you look at if this product's cost is out of your budget.


As our Top Pick for Versatility winner, there's a lot to love about the Smartwool PhD Ultra Light. Our testers awarded it high marks in every category, making it one of the top scorers overall. We loved its soft feel and stretchy fit and found ourselves eager to use it no matter what we were doing outside. The naturally odor-free quality of wool helps make up for the lack of running-specific features, and while there are other shirts in this review well suited just for that, we appreciated how well-rounded this shirt was.

Lauren DeLaunay
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