The Atom LT from Arc’teryx is a legend. It’s been one of the popular synthetic jackets on the market for years, so much so that it has received few updates even as the competition continues to increase. It’s true that the Atom LT isn’t as breathable as newer options like the Patagonia Nano-Air and The North Face Ventrix, but it’s a super versatile all-rounder that looks and feels great. Below we break down the Atom LT’s warmth, water and wind resistance, breathability, weight and packability, fit and sizing, and more. To see how the Atom LT stacks up, see our articles on the best synthetic jackets and best midlayers.
 

Performance

Warmth

The Arc’teryx Atom LT has synthetic fill, so it won’t rival down fill in terms of warmth or packability. Having said that, this jacket makes a really nice fall and spring outer layer and also works great as a midlayer in cold conditions. It’s filled with 60g Coreloft insulation everywhere but the side panels, which are a stretchy midweight fleece. This puts it on par in terms of warmth with other leading synthetics like the Patagonia Nano-Air and The North Face Ventrix. In addition, the taffeta outer lining does a nice job at blocking wind, which definitely helps as well.
Arc'teryx Atom LT (zipper)

From our experiences, we are comfortable wearing the Atom AT down to about 40 degrees Fahrenheit without much in the way of layering. It certainly can go lower with a warm baselayer underneath or if you’re on the move and working up some body heat. But for static use, when temperatures drop toward freezing we’re switching to a down jacket or adding a shell overtop. For a similar design with more warmth, Arc’teryx also makes an Atom AR, which has a more substantial 120g Coreloft around the body and slightly less in the underarms (80g) and hood (60g). 
 

Water and Wind Resistance

The Arc’teryx Atom LT does a nice job in light to moderate precipitation and wind. The taffeta shell fabric feels slightly more substantial than other leading synthetics we’ve worn, and it’s finished with a DWR treatment that helps water bead up instead of soaking in. Fleece isn't a great wind blocker, so the side panels will let in a strong gust, but the hard face exterior repels moisture very effectively. Because of these characteristics, we wear the Atom LT around the Pacific Northwest in most rainy conditions. The jacket did soak through on one particular occasion when camping and standing in sustained rain (we neglected to bring a shell on that trip and got more than we bargained for), but it has performed admirably otherwise. And unlike down insulation, Coreloft will continue to insulate when wet.
Arc'teryx Atom LT (hood)


Breathability

A number of new synthetic jackets like the Patagonia Nano-Air and The North Face Ventrix are of the highly breathable variety, but the Arc’teryx Atom LT isn’t a standout in this regard. After doing just about everything in this jacket from running and mountain biking to cross-country skiing, we think of the Atom LT’s breathability as solidly middle of the road. The stretchy fleece side panels make it more breathable than a down jacket or a cheaper synthetic, but Coreloft falls short of Ventrix and FullRange (used in the Nano-Air) insulation for serious aerobic activity. It’s a terrific piece for moderate outdoor use and everyday wear, but for high performance use on a consistent basis, we would look elsewhere. To fill this void, Arc’teryx has released its Proton series with a more air permeable shell, lining, and insulation.  
Arc'teryx Atom LT (underarm)


Weight and Packability

At 12.7 ounces for a men’s medium, the Arc’teryx Atom LT Hoody is on the lighter end of the synthetic jacket spectrum. Competitors like the Nano-Air Hoody (14 oz.) and Ventrix Hoodie (15.5 oz.) weigh more for comparable levels of warmth, but those jackets do breathe better. And some other down mimickers like the Patagonia Micro Puff (9.3 oz.) are lighter but also less durable and versatile. Another popular all-rounder, the Patagonia Nano Puff, weighs 12.8 ounces, almost the same as the Atom LT. You can cut weight with a lightweight down jacket, many of which weigh around 10 ounces or less, but you do compromise in terms of temperature regulation and cost. 

The Atom LT does not come with a stuff sack nor does it pack into one of its own pockets. We’ve brought the jacket along on a number of adventures by stuffing it into its hood and putting it in our pack, which gets it down to roughly the size of an American football. But the shell fabric and insulation don’t compress as easily as down or other more packable synthetics.
Arc'teryx Atom LT (hiking downhill)


Comfort

Of all of the categories in this review, comfort is one of the areas where the Atom LT excels most. Simply put, we never want to take this jacket off. You can wear it hiking or climbing and then to the grocery store or bar afterward, all without missing a beat. The interior lining is soft and smooth to the touch, the stretchy sides give it a great fit, and the Coreloft insulation creates a pillow-like barrier from the outside world. In fact, the Atom LT is so comfortable that we frequently find ourselves wearing it indoors. All things considered, it’s one of the coziest and most versatile jackets we own.
Arc'teryx Atom LT (lining)


Durability

The Atom LT has 20-denier shell fabric (the higher the denier rating, or “D” for short, the thicker the fabric). This puts it around the middle of the pack: The Patagonia Nano Puff is very similar at 22D, while lighter weight options like The North Face ThermoBall (15D) and Patagonia Micro Puff (10D) are thinner. And you can go with a more burly shell like the Patagonia Nano-Air at 30D, but the denier rating doesn’t tell the entire story there. Because the Nano-Air is super soft, we’ve found that is shows wear more readily than the Atom LT and has a tendency to pill more quickly (Patagonia has addressed this complaint, however, in their recently updated Nano-Air).
Arc'teryx Atom LT (with pack)

In terms of longevity, we’ve put the Atom LT through the wringer and it just keeps on ticking. As we mentioned above, we’ve done a wide range of outdoor activities in the jacket, and worn it on a near daily basis for a couple of years and counting. Despite stuffing it into a pack repeatedly, coffee spills, and numerous machine washings, the Atom LT looks great for its age. This is about more than the denier rating—it’s the premium build quality and materials that Arc’teryx is known for.
 

Hood

It’s worth noting that we tested the Atom LT Hoody, and the jacket also comes in a non-hooded version that is $20 cheaper and 1.6 ounces lighter at 11.1 ounces total. In general, we prefer hooded jackets for everyday wear—the hood comes in handy for walking around the neighborhood on chilly days, and definitely for hiking or sitting around the campfire. More, Arc’teryx does hoods right: the Atom LT features a cinch around back, which is a rarity in the synthetic jacket category (competitors like the Patagonia Nano Puff and The North Face Ventrix do not). You also get the same 60g Coreloft insulation in the hood for some nice added warmth.
Arc'teryx Atom LT (hood 2)


Fit and Sizing

Like most Arc’teryx products, the Atom LT has a slim, athletic fit. We prefer this type of cut, which is great for active use and wearing as a midlayer, but it may limit your ability to layer underneath the jacket. If you prefer a baggier fit, Patagonia tends to run more middle-of-the-road than Arc’teryx including with its popular Nano Puff, and The North Face is downright boxy with its ThermoBall. It’s also worth noting that the Atom LT isn’t particularly long—we find that our medium fits us just right, but we wouldn’t want it to be any shorter. If you’re on the fence about sizing, it may be worth sizing up.
Arc'teryx Atom LT (Washington Pass)


What We Like

  • A super versatile synthetic jacket that toes the line nicely between everyday and performance use.
  • Super comfortable liner, insulation, and shell fabric (we can’t emphasize this enough).
  • Arc’teryx styling and build quality can’t be beat.


What We Don't

  • Not as breathable as newer synthetics like the Patagonia Nano-Air, The North Face Ventrix, and Arc’teryx’s own Proton series.
  • Not packable: the jacket doesn’t come with a stuff sack and doesn’t pack into one of its own pockets.
  • Like most Arc’teryx products, the Atom LT is pricey.

Arc'teryx Atom LT (hiking)


Comparison Table

Jacket Price Weight Insulation Fabric Packable
Arc’teryx Atom LT Hoody $259 12.7 oz. Coreloft (60g) 20-denier No
Patagonia Nano Puff Hoody $249 12.8 oz. PrimaLoft Gold Eco (60g) 22-denier Yes
The North Face ThermoBall $220 13.8 oz. ThermoBall (33g) 15-denier Yes
Patagonia Nano-Air Hoody $299 14 oz. FullRange (60g) 30-denier No
The North Face Ventrix Hoodie $220 15.5 oz. Ventrix (80g) 30-denier No
Arc'teryx Atom AR Hoody $299 16 oz. Coreloft (120g, 80g, 60g) 30-denier No


The Competition

We consider the Arc’teryx Atom LT to be the premier all-around synthetic on the market (it currently holds the top spot in our roundup). Another popular option is the Patagonia Nano Puff, which is similar in weight (12.8 oz. vs. 12.7 oz. on the Atom LT) and shell fabric (22D vs. 20D), but uses PrimaLoft Gold insulation instead of Arc’teryx’s Coreloft. We think that Primaloft Gold is a slightly better insulation type overall and packs down smaller, but the liner and shell fabric on the Atom LT make it the winner in our book. The Arc’teryx is even more comfortable than the Nano Puff while offering similar protection against moisture and wind, not to mention we prefer the athletic Arc’teryx cut compared to Patagonia’s traditionally baggier styling. Both are great jackets for outdoor and everyday use, but we give the nod to the Atom LT.
Atom LT Thermoball comparison

Two other leading synthetic jacket contenders are the Patagonia Nano-Air and The North Face Ventrix. Both are designed primarily with active use in mind—think rock climbing and backcountry skiing—but we frequently see these jackets around town as well. Differences include the softer and stretchier shell fabrics, which are great for movement but have some impact on weather protection and durability. All in all, we like the Atom LT for all-around use, but the Nano-Air and Ventrix are the premier active insulation pieces.

From the in-house side, Arc’teryx has a number of other synthetic jackets to choose from. As mentioned above, the Atom AR is the thicker version of the Atom LT with 120g Coreloft around the torso instead of 60g on the LT. And the newer Proton line is designed to be more air permeable than the Atom with a thinner lining. The Proton AR is the most popular of the bunch, with 90g Coreloft Continuous around the body, while the Proton LT (see our in-depth review), has 65g. We find that the Proton line does run considerably cooler than the Atom line, which makes it the layer of choice for high-output activities. 

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