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Marmot Atom

rated 5.0 of 5 stars

The Atom has been discontinued. If you're looking for something new, check out the best warm weather down sleeping bags for 2024.

photo: Marmot Atom warm weather down sleeping bag
Version reviewed: Long

Everything I could want in a 3-season bag, until large cold spots appeared.


  • Very light
  • Very compressible
  • Amazing warmth for the weight
  • Roomy

To be brief, I think this bag lives up to the hype it's gotten. It is shockingly light and compressible, and very cozy and warm down to its 40 degree rating. I'm a cold sleeper and I always have at least one layer of clothing on when I sleep, but I've been comfortable on many cool northwoods summer/fall nights.

I bought the long version (I'm 6'4") and it's roomy enough to suit my side or otherwise awkward sleeping position preference. I've used it for several 1-2 night trips this summer and a week-long stint on Isle Royale this past September. So far it has performed flawlessly! Doesn't hurt that I found it for $100 off the MSRP.

Edit 9/15: Two years after purchase, a pretty large cold spot has formed on the top in the torso area. The down seems to have almost completely disappeared from two whole baffles, which is...baffling, considering there have never been punctures in either.

There is still a small amount of down clumped towards the side of one of these baffles, which I can't get spread back into the whole baffle, even after washing and drying the bag carefully.

My overall impression of the Atom is still good, but it is not nearly as warm as it was new. I should see what Marmot has to say about it.

Source: bought it new
Price Paid: $200

So far as I am concerned Marmot is the Technical gear leader these days. Before I would have told you this was The North Face, but everything Marmot builds or creates is just better. This bag is no different.

I have been using the Marmot Helium bag but wanted a summer bag as well. I thought long and hard about getting a down summer bag. The Helium I use in below freezing temps, so not too much to worry about with water soaking the down. The Atom will be used in rain storms so you better have a good tent that’s going to stay dry if you use this bag.

This bag is everything as advertised. It's as roomy as the Helium (I'm 6’1" and 240 lbs) and I am very comfortable in the long version Atom. This thing packs down to nothingness so much so I have been able to downsize my backpack. The room that is normally reserved for sleeping bags of the past is now used for other stuff. As a result I just don’t need as much room. Temperature rating is again understated if anything. A pair of long johns, a cap, and I think I'd be happy down to 25 degress.

The reason that this bag is better then the Helium is because Marmot somehow found a way to drop the price of the bag compared to in the past. The reason it's worse is for some reason Marmot can no longer guarantee 900 fill down.

Design: Mummy
Fill: 850 +
Temperature Rating: 40 degree
Weight: 1 lbs 4 oz
Price Paid: $150

Great all around bag! Like the other reviewers, I took my Atom down to the mid 30's and was very comfortable. Weighs nothing and extremely comfortable; plenty of room. I'm extremely impressed with this bag, I might just go buy a Helium for those colder nights.

Design: Mummy
Fill: 850+
Temperature Rating: 40
Weight: 1lb 3 oz
Price Paid: $150

This bag is as promised. I slept comfortable in temps in the mid to lower 30's. This bag also packs down to next to nothing, don't use the stuff sack that comes with it because it's too big, you can go much smaller.

Design: mummy
Fill: 850 fill down
Temperature Rating: 40 degree farenheight
Weight: 16 ounces
Price Paid: $189

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Regular Long regular long
Price MSRP: $279.00
Historic Range: $89.83-$318.95
Reviewers Paid: $150.00-$200.00
Weight 1 lb 5 oz / 610 g 1 lb 8 oz / 680 g - -
Fill Weight 8 oz / 226 g 10 oz / 283 g - -
Temperature Rating 40 F / 4 C 40 F / 4 C - -
EN Comfort 50.5 F / 10.3 C 50.5 F / 10.3 C - -
EN Lower Limit 43.2 F / 6.2 C 43.2 F / 6.2 C - -
EN Extreme 18.7 F / -7.4 C 18.7 F / -7.4 C - -
Fill 850 Fill-Power Down 850 Fill-Power Down - -
Shape Mummy Mummy - -
Max User Height - - 6 ft 0 in / 180 cm 6 ft 6 in / 200 cm
Hip Girth 58 in / 147 cm 58 in / 147 cm - -
Foot Girth 40 in / 101 cm 40 in / 101 cm - -
Price $279.00 USD $299.00 USD - -

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