Reviews You Can Rely On

Marmot Phase 30 Review

A high-quality hooded mummy bag that is significantly lighter than a standard backpacking bag
marmot phase 30 ultralight sleeping bag review
Credit: Marmot
Top Pick Award
  • 1
  • 2
  • 3
  • 4
  • 5
Price:  $426 List
Manufacturer:   Marmot
By Andy Wellman ⋅ Senior Review Editor  ⋅  Nov 4, 2019
  • Warmth - 30% 6.0
  • Weight - 25% 7.0
  • Comfort - 20% 7.0
  • Versatility - 15% 8.0
  • Features - 10% 7.0

Our Verdict

Marmot updated the Phase 30 since our test period.
Warmer than the fully hooded mummies lighter than it
Comfortable liner material
Roomy footbox
¾ length zipper
More suitable for 40F temps than 30
No neck baffle
Zipper catches on fabric easily
The Marmot Phase 30 is a fully hooded mummy bag that is comfortable, more versatile than most fully hooded ultra-light mummies due to its nearly full-length zipper, and is lightweight. While it wasn't the highest scorer in our review, it was pretty close. We chose to recognize it as our Top Pick for Weather Resistance due to its combination of naturally water-resistant Pertex Quantum material, combined with DWR treated 850-fill power down. While this doesn't mean that this bag could get soaked through and still provides the same amount of insulating loft as synthetic material, it does mean that it is better suited than most down bags we tested to handle wetter climates (given that you still take every precaution to keep it dry and air it out whenever possible). While we managed to find a few minor flaws, we think this is a quality ultralight bag that is worth investigating for those worried about water.

Our Analysis and Test Results

As we have already mentioned, we chose to award this bag our Top Pick because of its water-repelling capabilities. Many other bags also used treated down in their construction, but we chose to recognize the Phase 30 because it scored higher in our overall ratings.

Water Resistance
Perhaps a little disclaimer is in order. While we recognized this bag for its water resistance, we don't want to suggest that this bag is waterproof. In our testing, we found that the Pertex fabric caused condensation to bead up on the surface, but if it was rubbed too much, some would absorb into the face fabric. However, we also found that the capillary wicking action caused it to dry literally within about 30 seconds of airing in the sun in the morning. It was not possible to completely test the claims Marmot has made about their Down Defender treatment, but on an especially dewy night with heavy condensation inside our tent, we suffered from no loss of loft. In short, while the technology in this bag is noteworthy and valuable, the user should still take all precautions to keep their equipment dry for greatest safety.

Performance Comparison

marmot phase 30 ultralight sleeping bag review - the phase 30 ready for a solid night sleep in the desert where the...
The Phase 30 ready for a solid night sleep in the desert where the temperatures this October night got down to around freezing.


We have to admit we are a bit bothered by the fact that the Marmot Phase 30 did not exactly live up to its stated temperature rating. Once again, the EN tested comfort rating for this bag was 42F, and the limit rating was 33F, so we don't know where the number "30" is coming from. Regardless, we tested this bag during October nights that went down to about 32F, or freezing, and were a bit chilly, even when wearing long underwear as well. We conclude that it is better to think of this bag as a 40F bag.

marmot phase 30 ultralight sleeping bag review - this bag is sewn with wide, box baffle construction and filled with...
This bag is sewn with wide, box baffle construction and filled with hydrophobically treated 850 fill-power down.

What we liked was that it was a full zip hooded mummy. The zipper has an effective draft tube, and the hood is broad and covers the entire head, leaving only a small hole for the face. These features add to the warmth and make it a decent choice for three-season use, even if it is a bit on the thin side. For those who wish to use this bag during colder nights than we did, laying clothing inside will be a must.

marmot phase 30 ultralight sleeping bag review - printed on the zipper baffle is the results of en testing. as you...
Printed on the zipper baffle is the results of EN testing. As you can see, this bag is prepared to keep you comfortable at 42F, and its lower limit is registered as 33F, which is probably why we felt a bit chilly on this freezing night.


On our independent scale, our regular sized bag registered 18.3 ounces, with another 0.9 ounces for the included stuff sack. This was a bit heavier than advertised on Marmot's website, but still light enough for long-distance adventures. We also thought this bag stuffed down pretty small in the included sack, so it won't take up extra room in your pack, while also providing a hood and full enclosure.

marmot phase 30 ultralight sleeping bag review - showing the size of the phase 30 when it is stuffed inside its...
Showing the size of the Phase 30 when it is stuffed inside its included stuff sack. While it isn't the smallest stuffed sleeping bag we tested, its hard to complain about this size.


For testing, we ordered a regular size Phase 30 (it also comes in long), and while it wasn't stated anywhere on Marmot's website, this bag is designed for people up to 6'0" tall. Our head tester is 5'11", and thought that this bag was of perfectly adequate length. It also features an anatomically constructed foot box, giving the feet the room they need to be natural while enclosed. We certainly enjoyed this feature but found the amount of space in the legs and lower torso to be a bit tight, especially when wearing extra clothes.

Other features contributed positively to this bag's level of comfort. The Pertex 10d fabric used for both the face and inside liner is soft and slippery to the touch, and we found it to be very comfortable for sleeping in, with little friction between the liner and the clothes we were wearing. We also thought that the hood fits well, was very cozy, and we were happy that the drawcord easily rested outside of the bag, so it didn't hit us in the face as we slept.

marmot phase 30 ultralight sleeping bag review - showing the footbox of the phase 30, where you can see the stitching...
Showing the footbox of the Phase 30, where you can see the stitching that expands the footbox into a larger, more anatomically correct size than the relatively narrow legs above. We enjoyed this feature for comfort, and hope it is a feature that catches on with other bags in the near future.


There is no doubt that versatility is the Phase 30's strongest suit, although it didn't register as high as some of the quilts that we tested. While it wasn't the warmest bag available, the fact that it can be fully enclosed and zipped, with a warm hood, made it a good choice for stretching your thru-hike deep into autumn. Likewise, the fact that it offers nearly a full zip meant that it was far easier to ventilate than nearly any other ultra-light mummy bag.

What set it apart was the reason that we awarded it our Top Pick, the fact that it features both a superior water-resistant Pertex Quantum nylon face and liner fabric, and combines it with treated down on the inside.

marmot phase 30 ultralight sleeping bag review - a shot of the pertex quantum 10d face fabric as it causes water...
A shot of the Pertex Quantum 10d face fabric as it causes water sprayed on it to bead up without absorbing into the fabric. This water resistance is the first line of defense against your down getting wet and losing its insulating value.

Although you must still be careful to keep it as dry as possible, we think this bag makes a decent choice for those tackling the PCT, who might be concerned about the rain they will inevitably encounter once they hit Oregon and Washington, or the AT, who could encounter deluges almost anywhere. There is no doubt this is a bag suitable for epic thru-hikes.

marmot phase 30 ultralight sleeping bag review - pertex quantum uses capillary wicking action to dry out quickly...
Pertex Quantum uses capillary wicking action to dry out quickly. Even after a night of heavy condensation inside our tent and on the bag, it dried out in about 30 seconds, as long is it took to snap a photo.


The Phase 30 has an interesting combination of unique features that we didn't find on any other ultra-light bag, combined with some widespread features that didn't perform as well as we would have liked. Its unique offerings included a small internal pocket with a zipper just big enough for a small smartphone (our older iPhone 5 barely fit). Its position is on the side of the chest, so you don't risk rolling over and smashing whatever you put in there. We thought it was nice for a cell phone to keep the battery alive on cold nights, but wouldn't think of using it for our glasses, just in case we did roll over. It also has a glow-in-the-dark pull tab on the zipper so you can quickly find it once the headlamp has been shut off, but was also dim enough so as not to be distracting from our zzz's.

While these features are nice, we would have liked to see the standard features perform a bit better. In particular, we found that the zipper, which is a tiny gauge to save weight, has the habit of catching on fabric two or three times per night. While there is a more durable zipper guard fabric in place, it didn't work as well as we would have liked. We were also missing a neck baffle, although we were able to tighten up the facial opening till it was a tiny hole, and barely allowed in any air.

marmot phase 30 ultralight sleeping bag review - one of the unique features is an interior zippered pocket that is...
One of the unique features is an interior zippered pocket that is big enough for a small smartphone, and rests on the top side of the chest.


The price puts in on the higher side of average. Since it scores pretty comparable to these bags in our overall rankings and was worthy of recognition as a Top Pick, we think this presents a pretty good value.

marmot phase 30 ultralight sleeping bag review - here you can see the very deep and thick hood, which does a great...
Here you can see the very deep and thick hood, which does a great job of comfortably wrapping the entire head. On the near side is the single yellow draw cord, which tightens the top of the hood but not across the collar. We liked how this cord rests outside of the bag when sleeping.


The Marmot Phase 30 offers all the great advantages of an ultra-light sleeping bag, such as super lightweight and great packability, while also suffering from their common drawbacks — not super warm, fairly expensive. We love its versatility and think it is a great choice for those who want an ultralight mummy bag rather than a quilt, but don't want to pay the price in ounces.

marmot phase 30 ultralight sleeping bag review - the phase 30 is a great addition to your ultralight kit and is...
The Phase 30 is a great addition to your ultralight kit and is versatile enough to stretch into three season use, while also offering solid resistance against water and condensation.

Andy Wellman
You Might Also Like

Ad-free. Influence-free. Powered by Testing.

GearLab is founded on the principle of honest, objective, reviews. Our experts test thousands of products each year using thoughtful test plans that bring out key performance differences between competing products. And, to assure complete independence, we buy all the products we test ourselves. No cherry-picked units sent by manufacturers. No sponsored content. No ads. Just real, honest, side-by-side testing and comparison.

Learn More