Along with choosing the perfect hiking boots, packing a great sleeping bag is perhaps the single most important aspect of preparing for any outdoor adventure. Seriously, getting a good nights’ rest out on the trail can make all the difference between loving your adventure and hating it! A great sleeping bag is one that keeps you warm and dry without being unduly bulky and heavy. If you have ever carried an overloaded backpack, then you know what the golden ‘weight to warmth ratio’ is all about. Happily, this is exactly what I found in the REI Magma 15!

REI’s diverse line of sleepings bags has grown over the decades and of this year, the Magma 15 offers the most efficient weight to warmth ratio of any of their sleeping bags. For world travelers and hikers, this fact is music to our ears.

Whether you are traveling the world or trekking in the mountains, lightweight is always best. A sleeping bag can easily end taking up a ton of room in your backpack (I’ve been there), so when a sleeping bag comes around once in a blue moon that delivers toasty warmth in an ultralight package—at a competitive price— you better believe that I’m paying attention.

Recently I took the REI Magma sleeping bag out for a test run (well, a test nap) in the chilly, green forests of the Pacific Northwest, USA. Below, I’ll breakdown everything I learned through my experiences with the Magama 15.

This REI Magma review covers ALL of this sleeping bag’s juicy details including, key features and performance, weight, materials used, price, comfort rating vs. limit rating, sizing options, competitor comparison and a whole hell of a lot more.

Winter is coming John Snow, and its time for you to get to know one of the best lightweight sleeping bags for backpackers on the market today.

Get cozy and settle in…

*Note: This review cover’s the men’s version of the Magma 15, however, all of this same information can be applied to the women’s Magma 15 as well.

rei magma review
Welcome to my REI Magma 15 review!

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REI Magma Review: What Makes this Sleeping Bag Awesome?

Here are some of the big questions this Magma 15 review will answer:

  • What is the comfort rating of the Magma 15?
  • What insulation does the Magma 15 use?
  • Is the Magma 15 a true ultralight sleeping bag?
  • Can I use the Magma 15 for thru-hiking the Appalachian Trail or PCT?
  • What size should I choose? Long or regular?
  • Is the Magma 15 waterproof?
  • How does the Magma 15 compare to other sleeping bags in its temperature rating class?
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REI Magma 15: Key Features and Performance Breakdown

Choosing the right sleeping bag is an important decision. Your entire backcountry/camping experience can be made or broken based on the performance of your sleeping bag. As most of us humans sleep for at least a third of every 24 hour cycle, you will be spending lots of time cocooned inside your sleeping bag— and you want the experience to be awesome.

After exerting yourself on the trail all day, having confidence and trust in your sleeping bag is as important as believing that your car brakes will work or that the pilot flying the plane knows what he/she is doing. A sleeping bag is a very intimate piece of gear as it literally surrounds your body, keeps you safe in dangerous conditions, and provides the means to a restful night’s sleep—which is crucial to maintaining proper energy levels whilst out on an adventure.

First up, this is a 3-season sleeping bag meaning it is generally good to use in cold, but not freezing conditions.  As far as 3-season sleeping bags go, the REI Magma 15 is an attractive option on many levels.

Let’s take a look at what makes the REI Magma 15 the down-filled powerhouse that it is…

rei magma review
The REI Magma 15 in its natural habitat.

Magma 15 Warmth Performance

What’s the most important feature of a sleeping bag? The answer is obvious: to keep you warm, comfortable, and rested. If you have ever spent a never-ending night shivering inside a mediocre sleeping bag, then you know already: it’s the worst.

So does the Magma 15 actually deliver what it claims to deliver? At first, I admit I was skeptical. Compared with my Marmot Lithium 0 sleeping bag (a badass sleeping bag by the way), the Magma 15 felt super thin and light in comparison. As I headed off into the brisk Oregon wilderness I was thinking to myself, “well at least I have plenty of layers“.

With temperatures hovering in the high 30’s range (Fahrenheit which is about 1 degree celcius), I slipped into the Magma 15 and settled in for the night. My first impressions were good. The Magma 15 is roomy enough for me (I’m slender, 5’10, 165 lbs), without being drafty. I had the bag zipped up about 90% for most of the night including having my head tucked inside the hood.

The contoured hood holds warmth while providing room for a low-profile pillow (not included) and two different hood drawcords allow for internal adjustment to avoid heat escaping.

rei magma review
For near-freezing temperatures, definitely employ the hood.

Whilst camping, I typically sleep in underwear, no socks, and a base layer top (calm down ladies…). The trapezoidal “foot box” did a fine job of insualting my feet. The toe box baffle system does what its suppossed to do: keeping feet toasty.

Additional puffy insulation around the neck and shoulders provide additional warmth and protection to the areas where heat normally escapes. The strange thing about this insulation yoke is that it is only on one side of the bag. This means that if you are not fully zipped into the bag then the extra insulation doesn’t really help.

At no point in the night was I overly warm (but I was certainly cozy) which tells me that if the temperature dropped another 10-15 degrees, I would really be pushing the bag’s limit. Which brings me to my next point…

rei magma review
When fully zipped up, the insulation “yolk” helps keep the warmth loacked in.

Magma 15 Comfort Rating vs Limit Rating

Understanding the difference between the comfort rating and the limit rating is very important. Don’t let the name of the sleeping bag fool you. The Magma 15 does not have a comfort rating of 15 degrees Fahrenheit (which would be -10 c).

The Magma 15 is an ultralight 3-season sleeping bag, not intended for winter use. Every person has a different sensitivity to temperature. For example, I identify myself as a warm sleeper, whereas others identify as cold sleepers. If you are not sure which you are, then ask your significant other or call up that girl you once hooked up with back in college.

On average the Magma 15 comfort rating is around 28 degrees Fahrenheit (-2.2 C). Once you start dipping below that number you may still be warm, but not necessarily super toasty and your sleep may be disrupted.

The Magma 15’s lower limit rating is 16 degrees F (-8.9 C). Note that temperatures below 16° F fall into the extreme lower limit category. The extreme lower limit basically means that the sleeping bag will be able to keep you alive up until a certain threshold temperature but offers no guarantees thereafter. REI does not provide an extreme lower limit rating for this sleeping bag. Typically, the extreme limit is around 15° less than the lower limit rating. For the Magma 15, the extreme lower limit probably between  0° and -7 ° F (-20+ C).

With temperatures around 30° F or higher though, the Magma 15 is an excellent performer. For 90% of all your late spring, summer, and early fall adventures, the Magma 15 offers more than enough warmth, even if you fall into the cold sleeper category. Combined with a super warm pad like the ThermaRest NeoAir XLite NXT, it’s great for a variety of different climates.

In summary, this sleeping bag is absolutely not intended for use in extreme winter conditions. This means don’t take it up Everest Base Camp, don’t take it to see the Northern Lights and don’t use it to sleep rough during London or New York winters…

rei magma 15 review
Know the difference between comfort and limit.

Magma 15 Weight: A Powerful Sleeping System in an Ultralight Package

Good quality ultralight backpacking gear usually costs serious money and can easily be over your price limit. When it comes to saving weight one usually has to pay for the pleasure.

Whilst the Magma 15 is far from dirt cheap, it does offer a lot of bang for your buck with regard to its weight-performance ratio. Weighing in at just 1 lb. 14.6 oz., you’d be hard-pressed to find another ultralight sleeping bag with a similar temperature rating at the same price point ($369).

The Magma 15 doesn’t make us have to decide between having a comfortable hiking experience vs a comfortable camping experience. You can have both! Of course, saving weight isn’t just a bonus perk for hikers.

I am constantly traveling with a large amount of gear. Sometimes I am abroad for months at a time and I need to have my whole kit with me (including my alpine gear). The Magma 15 is the perfect 3-season sleeping bag option for travelers for the simple fact that it doesn’t weigh much and can be compressed into a 13-liter stuff sack. Honestly, you can fit the Magma 15 into a 10-liter compression sack (see below). It packs down super small! Ultralight backpackers rejoice.

Of course, an ultra-light backpack also helps to reduce weight if that is your goal.

rei magma 15 review
The Magma 15 packed into a 13-liter Sea to Summit dry sack.

Insulation: Down Fill for the Win!

So what the hell is inside the Magma 15 that makes it so soft and warm? 850-fill-power goose down…that’s what!

Known for being lighter and warmer than synthetic down, real down is where it’s at if you’re looking to maximize the ever-important weight to performance ratio. Out of the bag, the Magma 15 has a decent loft, which is key to making the most of a down sleeping bag.

Remember, when storing any piece of down gear and especially down sleeping bags, you NEVER want to store the sleeping bag in a compression sack. This causes the down to compress and bunch up in weird places.

The goal should be to maintain the bag’s loft so that the insulation is evenly distributed. To help with storage, the REI Magma 15 comes with a large mesh storage sack.

rei magma 15 review
Keep that beautiful loft!

What does 850-fill power mean? Technically speaking fill power is a measurement of the amount of space one (1) ounce of down will occupy in cubic inches when allowed to reach its maximum loft. … So 850 fill power will rise or “loft” higher than 800 fill power. The higher the fill power the larger the down cluster. Basically what this means is having 850-fill power wrapped around your body will provide more warmth and insulation than a 600-fill power sleeping bag.

While the Magma 15 is NOT waterproof (no down stuff ever is) it is made using a Downproof Pertex shell and water-resistant down. The supple 15-denier lining combines to provide sustained coziness and a supersoft feel. If you are inside a good camping tent rather than sleeping in a stream, you should be ok.

Where does the down used in the Magma 15 come from you ask? REI being the thoughtful and responsible gear manufacturer that they are only using down certified to the Responsible Down Standard (RDS) in REI sleeping bags. The Responsible Down Standard aims to ensure that the down feathers come from animals that have not been subjected to unnecessary harm or cruel treatment.

sustainable down feathers
RED Down Feather Standards.
Photo: RDS

Magma 15 Zippers: Anti-Snag Zips

Do you ever feel like breaking something every time a zipper gets jammed into the fabric of your sleeping bag? Your cold, you’re in a hurry, and you just want the damn sleeping bag to zip as it should. I mean why do they design zipper tracks to essentially feed right into fabric? Why??

Take a second to breathe and reflect on this good news: the Magma 15 is equipped with a new zipper cover and internal *anti-snag* strip that combines for painless zipping. Painless I say! Thank God. A hybrid zipper path provides easy access along shoulders and torso so you can easily open or close the sleeping bag without having to search for the track.

One should never have to get frustrated with sleeping bag zippers. REI understands this basic concept and has developed a zipper system that is actually functional. As always, remember to take your time with the zippers (even if you are cold) to ensure that they keep performing at a high snag-free level for many years to come.

rei magma 15 review
Behold: anti-snag zippers.

Magma 15 Sizing and Fit

The Magma 15 comes in two sizes: Long – Left Zip (1 lb. 14.6 oz.) and Regular – Left Zip (1 lb. 12.3 oz.).

The obvious difference between the two sizes is that the long-left bag is—you guessed it— longer. The long-left size is better for taller humans looking to be able to stretch out all the way. If you are between 6′ and 6’5, you are going to want to go with the long size.

As mentioned, I am 5’10 and use the regular size. If you too are of average height it would be a mistake to go with the longer sleeping bag. Having more air space at your feet means that there is more surface area to warm up. If you have six inches of unoccupied space at the bottom of the sleeping bag your toes will certainly feel it.

For the long-left sleeping bag size, sorry tall folks, you’re going to have to pay $20 more for the extra room ($389).

Designed with generous knee and foot space and a fitted silhouette that maximizes warmth capabilities, the Magma 15 still is a mummy-style sleeping bag. Even if you are a slight person don’t expect to have a TON of extra room inside the sleeping bag. I personally find mummy bags to be warmer than the more square cut sleeping bags. I will always prioritize warmth and lightweight over personal space within the bag. I recommend you do the same.

rei magma 15 review
The REI Magma 15 size regular-left zip.

Whilst the bag is pretty roomy, it’s not big enough for two. If that’s what you’re looking for check out the Rei Siesta 20 double sleeping bag.

Is the REI Magma 15 Fit for a Thru-Hiker’s Kit?

When I hiked the Appalachian Trail a few years ago, I did so with an REI Trailmade 20 sleeping bag (2lbs. 11 oz.). After June brought warm weather to the mountains, I mailed my sleeping bag home and continued hiking with a sleeping bag liner only.

(Pssssttt – Wondering if you need a sleeping bag liner? Then our guide to the best sleeping bag liners will answer all your questions!

The Magma 15 is almost a pound lighter than the Trailmade 20, making it a more ideal option for long-distance hikers overall. If you start you hike in early March as I did, you’ll need a sleeping bag that can keep you warm in a snowstorm (it snowed on me three times on the AT), but won’t weigh down your pack.

Most thru-hikers would agree that a warm sleeping bag weighing in at 1 lb. 14 oz. is a hell of a good value. Carry more frosted donuts and less in sleeping bag weight. It’s that simple.

hiking the appalachian trail
Hiking the Appalachian Trail in 2015.

REI Magma 15 Price: Paying for the Pleasure

Price: $369.00 USD.

If you have a look at some of REI’s other sleeping bag options, you may quickly ask yourself “why is the Magma 15 so much more expensive?” It is true that REI is famous for providing quality gear priced waaaaay lower than some of the leading brands out there.

I would argue that that fact still rings true when it comes to the Magma 15. The honest truth is that if you want to step into the realm of an ultralight down sleeping bag it comes at a price. Synthetic sleeping bags are always going to be cheaper and they are always going to be heavier and bulkier.

For what you get in return, splashing out the $369 bucks on the Magma 15 is well worth it in my opinion. That said it is not the cheapest option. If saving money is more of a priority than saving weight, you do have some interesting alternatives.

The Nemo Disco 15 costs $299.95 and offers a similar amount of warmth performance. It also weighs a pound more than the Magma 15 and though it can be compressed to 7.2 liters(!) versus the 10 of the Magma (you could also probably compress the magma into 7 liters too). Another fine sleeping bag is the Big Agnes Anvil ($349,95). The Anvil 15 comes in three sizes (regular, long, and wide) which may make for a more comfortable fit if you are a large person. Again, the Anvil 15 weighs nearly a pound more than the Magma 15.

If you are looking for the cheapest quality option and don’t mind a little extra weight, the above mentioned REI Trailmade 20 should get the job done for you.

Let’s now take a closer look at how the REI Magma 15 stacks up against the competition…

rei magma 15 review
It’s hard to find a superior sleeping bag with a better weight-warmth-price ratio.

REI Magma 15 vs the World Comparison Table

rei magma sleeping bag for backpacking

REI Magma 15

  • Price > $369
  • Weight > 1 lb 14 oz.
  • Insulation > 850-fil water resistant down
  • Comfort Temperature Rating > 28 F
REI Co-op Trailmade 20 Sleeping Bag - Nic

REI Trailmade 20

  • Price > $99.95
  • Weight > 3 lb. 4.6 oz.
  • Insulation > Synthetic
  • Comfort Temperature Rating > 21 F
REI Co-op Zephyr 25 Recycled Sleeping Bag

REI Zephyr 25

  • Price > $159
  • Weight > 2 lb. 11 oz.
  • Insulation > Synthetic
  • Comfort Temperature Rating > 25 F
REI Coop Siesta Hooded 20 Sleeping Bag

REI Siesta 20

  • Price > $139
  • Weight > 5 lb 14 oz.
  • Insulation > Synthetic
  • Comfort Temperature Rating > 20 F
Nemo Disco 15

Nemo Disco 15

  • Price > $299
  • Weight > 2 lb. 15 oz.
  • Insulation > 650-fill down with Nikwax
  • Comfort Temperature Rating > 25 F
Big Agnes Anvil 15

Big Agnes Anvil

  • Price > $269.95
  • Weight > 2 lb. 10 oz.
  • Insulation > 650-fill-power DownTek down
  • Comfort Temperature Rating > 28 F
Big Agnes Torchlight

Big Agnes Torchlight 20

  • Price > $319
  • Weight > 2 lb. 12 oz.
  • Insulation > 7Downtek™ 750FP water repellent down
  • Temperature Rating > 28.5 F
best quality sleeping bag feathered friends swallow nano 20

Feathered Friends Swift 20 YF

  • Price > $459
  • Weight > 1 lb 15 oz.
  • Insulation > 900-fill goose down
  • Temperature Rating > 20 F
Sea to Summit Spark

Sea to Summit Spark 2

  • Price > $309
  • Weight > 9.2 oz.
  • Insulation > 750-fill goose down
  • Temperature Rating > 50 F

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    REI Magma 15 Review: Final Thoughts

    Not all sleeping bags are created equal. By now, you should know all of the ins and outs of the REI Magma 15 and if it is the right sleeping bag for your adventures. My verdict? Despite its steep price tag, the Magma 15 delivers sustained and proven warmth in an ultralight package.

    Travelers and backpackers don’t need to sacrifice space and weight in order to be warm, which is huge. If you want to go with one sleeping bag that will cover all of your 3-season backpacking and international travel needs, you have arrived at the right place. The REI Magma 15 has my full blessing.

    Another attractive aspect of buying an REI product is its warranty program. If literally anything goes wrong with your Magma sleeping bag or you simply don’t like the color after a few uses, you can exchange it for a full refund or exchange. Not many other companies offer such sweet return policy.

    One of the best parts about setting off on any adventure is the feeling one gets when you know you are prepared with the right gear. Grab yourself an REI membership card and get yourself a Magma 15 sleeping bag and prepare for many years of blissful nights in the backcountry.

    What is our final score for the REI Magma 15 Sleeping Bag? We give it a rating of 4.7 out 5 stars!

    rei magma 15 review
    Whenever I’m cold, I’ll just look at this photo.

    What are your thoughts? Did this brutally honest review of the REI Magma 15 help you? Anything I didn’t answer? Let me know in the comments below – thanks guys!