REI Magma 15 Sleeping Bag Review

Bottom Line

The REI Magma 15 is one of our all-time favorite ackpacking sleeping bags when it comes to quality: it’s ultralight, ultra comfy, and much easier on your wallet than most bags with similar specs. We’ve used it for hundreds of nights camping and backpacking, from multi-day treks in the Montana Beartooths in summer to section hikes of the Colorado trail in late fall. With a comfort rating of 21°F, the Magma 15 is perfect for cold sleepers and camping below freezing. Its efficient mummy shape reduces dead space to retain as much heat as possible, and the bag’s awesome compressibility is a big win for backpackers trying to keep weight down. 

Even though the standard narrow sizing and mummy design might feel restrictive to some, the Magma also comes in inclusive wide and long sizes. Some warm sleepers might find the Magma 15 too warm for summer, but it also comes in a cooler 30°F option for milder conditions. If you’re looking for a warm, well-designed, compressible, and easy-to-carry sleeping bag for cooler temperatures, the Magma 15 is one of our favorite sleeping bags for backpackers of every skill level.

Warmth

The REI Magma 15 will keep you toasty warm overnight, even when the temperature dips well below freezing. Gear Analyst Ian Krammer has used this bag for years in frigid temperatures in the Rockies of Colorado, from backpacking in winter conditions above 10,000 feet to car camping in spring snow storms. Thanks to its high-quality down insulation and efficient design, the Magma 15 is comfort-rated to 21°F, making it perfect for cold-weather adventures.

The Magma offers a true mummy shape, including a snug fit that minimizes dead space to retain as much body heat as possible and a classic insulated mummy hood that cinches around your head. The oversized draft collar and long, oversized draft tube along the zipper stop the cold from seeping in. REI uses premium down and we’re big fans of the inclusive sizing: the Magma 15 is non-gendered and comes in many different lengths and widths to accommodate all body shapes and sizes, so you can stay warm, comfortable, and get a rejuvenating night of sleep even when it’s freezing.

However, the Magma does have some drawbacks. The leg girth will feel a bit restrictive for some, especially if you prefer more room to move. Luckily, you can choose a wider size if that’s your preference. Like most warmth ratings, you’ll need to pair your sleeping bag with an insulated, high R-Value sleeping pad to stay truly warm in cold conditions. On the flip side, the Magma 15 will likely be too warm for summer backpacking, although you can always go with the lighter-weight Magma 30 if you’ll be backpacking in especially toasty or humid conditions.

Comfort

If your top priority is comfort, the Magma 15 is your golden ticket to dreamland. REI’s extensive size range means no matter who you are, you’ll likely find a snug and personalized fit. The mummy shape is not only excellent for retaining warmth but it’s super cozy and secure, making this one of our top picks for a good night’s sleep. The interior fabric is soft and pleasant against the skin, and it’s plenty warm down to around 21°F, so you’ll stay warm whether it’s a clear, cool night or a freezing evening. Its draft collar and insulated, cinchable hood keep the cold air out, so you’ll stay warm, nestled, and asleep all night long. Plus, we’re big fans of the intuitive zipper design, which wraps for easy access from off-center at the hood to the side of the bag for easy in and out while inside the Magma. 

That said, mummy bags aren’t for everyone: some find the design too restrictive since the narrow leg girth is tight if you like to spread out or move a lot in the night.

Weight & Packability

The REI Magma 15 is fairly lightweight and extremely packable, making it perfect for backpackers. At 2 pounds, 3.6 ounces, it is far from the lightest sleeping bag we tested, but it’s still considered ultralight and is an outstanding weight for short to moderate backpacking adventures. Though it’s a bit heavier than some of the options we tested, the Magma 15 is a stellar option for everyone from beginners to seasoned thru-hikers.

The down insulation compresses very well into the included stuff sack, measuring only 7.8 inches wide and 16 inches long. This high compressibility means the Magma takes up minimal space in your pack, leaving more room for essentials, and the stuff sack is effective for packing the bag down tightly. This combination of low weight and excellent packability is a slam dunk for traveling light and efficiently.

Like most ultralight gear, you’re sacrificing a bit of durability in favor of the featherlight design. While these airy materials are great for reducing weight, they don’t last as long against snags, tears, abrasion, dog nails, and consistent use as camping and backpacking bags that use heavier fabrics. The Magma 15 is super compressible, but after dozens of nights, the frequent compression diminishes the loft and insulation. While the zippers work well and get the job done, the teeth and zipper pull aren’t the most durable parts of the Magma after hundreds of uses, so you’ll want to be a bit more gentle versus heavier-duty camping bags.

Features

The REI Magma 15 is loaded with features that make it comfortable, versatile, and easy to use. We love the two separate drawcords – one around the face opening, another around the neck area – that can be adjusted from the inside, so you can dial in the fit exactly how you like it. The trapezoidal footbox allows for natural foot movement while reducing excess space, trimming down the weight. And, a large interior stash pocket easily holds small essentials like chapstick, a headlamp, or even your phone, making nighttime access easy. We also appreciate that REI includes a stuff sack for packing and a roomy mesh sack for breathable storage to retain the integrity of the loft and material.

Should You Buy the REI Magma 15?

We recommend the REI Magma 15 for backpackers headed into cool and cold nights that need a warm and efficient sleeping bag. With a comfort rating down to 21°F, this thing is perfectly suited for folks camping in the high alpine, the desert in spring and fall, or winter environments. The trim mummy shape and high fill power down offer excellent heat retention, making it a top choice for cold sleepers and all but guaranteeing cozy nights when temperatures drop. The Magma’s lightweight and packable design adds to its appeal for long treks.

However, the snug mummy-bag fit might not be ideal for those who like more space or are looking for a bag primarily for warmer conditions. If you’re headed into extremely cold temperatures or simply want an extra-roomy or more versatile design, the Magma 15 might fall short. Overall, it’s best suited for those prioritizing low weight, affordability, warmth, and efficiency in cold weather.

What Other Backpacking Sleeping Bags Should You Consider?

REI Magma Trail Quilt 30 Review: This is basically the quilt version of the Magma 15. It provides excellent warmth for cooler temperatures but with a lighter design. It’s a better option if you’re looking for something less bulky, though it won’t keep you as warm in very cold conditions because its temperature rating is lower.

Sea to Summit Spark 15 Review: The Spark 15 offers a similar temperature rating to the Magma 15, making it an outstanding choice for cold-weather adventures. This bag stands out for its lighter weight but lacks the Magma 15’s added features and also comes at a higher price point.

NEMO Disco 15 Endless Promise Review: Both the Disco 15 and Magma 15 are built for cold conditions, with comparable warmth ratings. The Disco 15 differentiates itself with a focus on sustainable materials, a mindful, eco-friendly construction, and a lower price, although it is heavier and isn’t nearly as packable.