Best Overall Model
Western Mountaineering MegaLite
: 1.63 lbs | Fill Power
: 850+ Goose Down
Warmer than its 30°F rating
Great warmth-to-weight ratio
Awkward hood closure
The MegaLite is our favorite backpacking sleeping bag because it performs well in all areas. Like other ultra-premium down bags, it offers an outstanding warmth-to-ratio in a bag that packs down extremely small. Unlike the other ultra-premium down bags we tried, it features spacious interior dimensions that supply superior comfort no matter your sleeping style. For virtually any overnight backcountry application, this is an excellent choice.
Our performance criticisms are minor: the hood closure is slightly awkward, and its zipper is good but not great. A more significant issue is a price that is likely to dissuade more than a few shoppers. We believe, however, that for dedicated users the considerable benefits of this and other high-end down bags are worth the exorbitant costs, especially when you factor in the outstanding longevity of their loft. The hard choice is deciding between the MegaLite — our favorite bag for the average backpacker — and other top-performers like the Feathered Friends Hummingbird UL and Western Mountaineering UltraLite.
Read review: Western Mountaineering MegaLite
The Best Deal and The Best for Wet Conditions
NEMO Kyan 35
: 1.89 lbs | Insulation
: 12 oz of Primaloft Silver
Packs super small
Retains significant warmth when wet
Great price for its warmth-to-weight ratio
Includes a functional compression sack
Doesn't live up to its 35°F rating
As a general rule, sleeping bags with synthetic insulation are larger and heavier than their down counterparts. Somebody forgot to tell the Nemo Kyan 35. It shocked us with its moderate weight and tiny packed size that was on par with several down bags at the same temperature rating. Also, its Primaloft Silver synthetic insulation is a much better choice for wet conditions because it retains a significant percentage of its warmth even when soaked. The cherry on top is the more than reasonable price tag.
The Kyan 35 attributes some of its low weight and small packed size to the lower insulation requirements for its 35°F temperature rating. In the field, our testers felt this rating was a little generous. We thus only recommend the Kyan for warmer three-season conditions. Nemo, however, offers a 20° version that appears on paper to provide similarly high performance for colder situations. Despite its warmth deficiency, the Kyan 35 is an excellent bag at a price that can't be beat.
Read review: Nemo Kyan 35
Best Budget Down Bag
Kelty Cosmic 20
: 2.63 lbs | Packed Size
: 8.7 liters
Decent weight and packed size
Suitable for backpacking
Low warmth-to-weight ratio
Below average comfort
No compression or storage sack included
Although the Kelty Cosmic 20 scores near the bottom of the field, it was up against many ultra-premium bags that cost up to three times as much. Sure, those bags are a lighter and they pack smaller, but you can sleep just as well inside the Cosmic using all the extra money you saved as a pillow. For a low price, you get a sleeping bag that supplies respectable levels of warmth and comfort at a weight and size that's still reasonable for backpacking. You also get the convenience of a stash pocket and the coziness of a neck baffle — two features that are missing on many of its more expensive rivals.
The Cosmic cuts its costs by using a mixture of 600 fill power down (83%) and synthetic fibers (17%) for insulation. This results in a bag that's a pound heavier and two liters larger inside your pack than comparably warm, 100% premium down bags. With the money you save, however, you can invest in a lighter tent or more packable sleeping pad to reduce the weight and volume of your overall backcountry kit.
Read review: Kelty Cosmic 20
Best for Fast and Light Adventures
Feathered Friends Hummingbird UL 30
at Feathered Friends
: 1.45 lbs | Fill Power
: 950+ Goose Down
Exceptional warmth-to-weight ratio
Best loft in the review
Exceptional anti-snag zipper
Noisy shell fabric
When saving weight takes precedence over everything else, one of our favorite bags is the Hummingbird UL. Feathered Friends uses the highest fill power down we've tried (950+) to create a bag that is exceptionally warm yet truly ultralight. Somehow this bag also manages to feature a sturdy full-length zipper that's virtually immune to snagging. The same zipper provides ample venting options and the possibility of sharing it as a quilt with a partner during a full-on bivouac.
It must be noted that the Hummingbird UL achieves its low weight with particularly narrow dimensions that many will find constrictive. Its ultra-high fill power down also comes with an ultra-high list price. If you can look past these faults you get a traditional sleeping bag that offers an unparalleled warmth-to-weight ratio. There may be no better choice when the ounces matter.
Read review: Feathered Friends Hummingbird UL 30
Best for Colder 3-Season Conditions
Western Mountaineering UltraLite
: 1.86 lbs | Fill Power
: 850+ Goose Down
Warmest bag in the review
Sturdy full-length zipper
Legit draft collar
Continuous horizontal baffles
Bulky packed size
Maybe too warm
If you know you "sleep cold" or have plans for higher elevation trips in the spring or fall, the Western Mountaineering UltraLite might be the best bag for you. With its 17 ounces of 850+ fill power down and a legit draft collar, our testers thought it was easily the warmest bag in the review. Also, its full-length zipper and continuous horizontal baffle construction allow enough venting possibilities to avoid overheating on hot summer nights. In the field, we were able to sleep comfortably in this bag across an expansive range of overnight temperatures from 10° to 55°F.
The drawback to this exceptional performance is a staggering price tag. We also believe that most 3-season travelers would be happier with a slightly less warm bag that can offer weight and packed size benefits. Nevertheless, if you're looking for an awesome bag that's assured to keep you toasty, the UltraLite is our favorite model.
Read review: Western Mountaineering UltraLite
Best for Exceptional Comfort
Sierra Designs Backcountry Bed 700
: 2.10 lbs | Insulation
: 700 Fill Power Dridown
Zipperless comforter-like closure
Convenient foot vent
Great for tummy sleepers
Heavy for its warmth
Drafty in colder weather
This bag lives up to its name by bringing the comfort of an ordinary bed to the backcountry. Its zipperless design features a comforter-like flap that you can fold open or closed to get your temperature just right. The notably roomy dimensions also mimic the freedom of movement you enjoy with a regular blanket, ensuring that you have plenty of space to stretch your legs or roll over.
The drawbacks to this exceptional comfort are the extra materials that its design require, which add weight and bulk to the overall bag. Its 35°F temperature rating also felt a little optimistic, so we suggest "cold sleepers" consider the Sierra Designs Cloud 20 for regular use in spring or fall. Nevertheless, with the Backcountry Bed, Sierra Designs has created an exceptionally comfortable bag that is sure to be adored by those who've long found the design of traditional sleeping bags unpleasant.
Read review: Sierra Designs Backcountry Bed 700
Sleeping bags offer the highest warmth-to-weight ratio of any outdoor gear so a good bag should be one of the most important pieces of your overall overnight kit.
Why You Should Trust Us
Lead author Jack Cramer is an accomplished climber, a National Outdoor Leadership School alumnus, and undeniable gear nerd. Co-author Ian Nicholson is an American Mountain Guides Association-certified guide who has helped over 1,000 clients select the right gear for backpacking, climbing, and ski trips. They have both spent the better part of the last decade in the backcountry and have consulted with Appalachian and Pacific Crest Trail thru-hikers, Yosemite Search and Rescue team veterans, professional outdoor athletes, and novice backpacker friends to ensure a diverse set of perspectives.
Our review team researched more than 100 of the most popular backpacking sleeping bags. We selected and purchased 16 of the best that today's market has to offer to undergo extensive testing. We measured warmth, weight and packed size in the lab. The remaining performance characteristics, such as comfort, versatility and design, were assessed in the spectacular landscapes of California's Sierra Nevada, Wyoming's Wind River Range, Grand Staircase Escalante National Monument, and Death Valley National Park. Bags went to elevations from 150 to 13,000 feet with nighttime lows between 10° and 70°F.
This review is also unique because it includes direct comparisons between Western Mountaineering and Feathered Friends products. These small, specialty manufacturers source some of the best goose down on the market, but their reluctance to give reviewers their products for free limits how many get reviewed. Fortunately, OutdoorGearLab's policy of purchasing all the sleeping bags we test gives us the flexibility to include both makers in this comprehensive review.
Related: How We Tested Backpacking Sleeping Bags
Analysis and Test Results
Designing a great backpacking sleeping bag is a tricky balancing act. Add extra insulation to make it warmer, and it quickly becomes too heavy. Trim the zipper's length to save weight, and you limit your options for venting excess heat. We selected six important performance criteria that are often at odds with one another: warmth, weight, comfort, packed size, versatility, and features & design.
Related: Buying Advice for Backpacking Sleeping Bags
Although the price is not a consideration in our performance scores, we know it's important to your purchasing decision. Sleeping bags come in a surprisingly wide range of prices for models that ostensibly serve the same purpose. After extensive testing we can confidently say that the price differences generally reflect meaningful performance differences.
The Nemo Kyan impressed us with its outstanding performance and surprisingly low price. We consider it one of the best sleeping bag deals out there.
In terms of absolute performance, nothing came close to the Feathered Friends and Western Mountaineering bags, which demonstrated clear superiority in overall design, build quality, and warmth-to-weight ratios. These bags, however, require most of us to save up to afford them. For less than half the price of these premium bags, the Nemo Kyan 35 or Kelty Cosmic 20 both offer exceptional deals. Although they're a little heavier and bulkier, once you get them to camp, you're likely to sleep just as well. The REI Co-op Magma 30 is another bargain worth mentioning. Although many won't consider its price to be cheap, it offers noticeable savings over the ultra-premium while still providing close to the same level of performance.
Your warmth in a bag is largely a function of the quantity and quality of the insulation. With down feather bags, you can get a rough sense of their warmth by examining the fill weight (quantity) and fill power (quality) of the down it contains. This task is trickier with synthetics where the overwhelming number of proprietary fibers makes comparison close to impossible. Further complicating matters is the design and fit of a bag. This has a smaller, but still significant, effect on warmth.
In an attempt to resolve this confusion, the European Committee for Standardization developed the EN 13537 standard, which is a test designed to determine sleeping bag temperature ratings that are consistent between different companies. These EN ratings seem to be more accurate than past manufacturer-advertised temperature ratings, but due to the added costs of testing, some of the best companies do not have their bags tested. Also, the complicated details of the testing protocols can arbitrarily favor certain designs that may not reflect real-world warmth.
The EN comfort, lower limit, and extreme temperature ratings listed on the Therm-a-Rest Hyperion. Our testers don't think it's quite as warm as these ratings.
Due to these issues, we chose to evaluate warmth using real human testers. We slept in each bag for at least three nights in a 48°F room. The performance was then assessed relative to the other bags we tried and their EN ratings if they had one. The difference between the warmest and coldest bags was much more significant than the official ratings would suggest. The same field tester, for example, slept comfortably in a Western Mountaineering UltraLite at temperatures 10° below its 20°F rating, and shivered in the Nemo Kyan 35 in temperatures 10° above its 35°F rating.
In climbing and mountaineering, and perhaps even more than long-distance hiking, weight is an important factor. You may have to make challenging technical moves with the weight of your sleeping bag on your back. Photo: An open bivy with the MegaLite under the stars while climbing the North Ridge of Forbidden Peak.
Our warmth ratings are scaled so that a score of ten indicates bags with the highest level of warmth, and a one, the least. Importantly, this doesn't mean that a bag with a ten would be the best possible bag for you. More likely, if you're looking for a bag for moderate 3-season conditions, a score of 7 or 8 will probably be sufficient. For most people, the bags with the highest warmth rating are better-suited for the colder nights of spring and fall.
While sleeping bags are foundational to staying warm during overnight stays in the backcountry, 100 percent of sleeping bags are designed to be used in conjunction with a sleeping pad and no model will perform anywhere close to its published rating without one.
Keep in mind that for your bag to keep you warm at its temperature rating, you will also need a quality sleeping pad and some protection from the elements.
Related: The Best Backpacking Sleeping Pads of 2020
Related: The Best Backpacking Tents of 2020
In contrast to warmth, weight is easy to measure. It is also is one of the most important considerations. A sleeping bag's weight is a consequence of the amount and type of insulation, the dimensions of the bag, the size and length of the zipper, and the density of the fabrics. Generally, higher quality materials weigh less but come with correspondingly high prices. Saving weight with a shorter zipper or trimmer fit is also an option but affects versatility or comfort.
To evaluate weight, we used our digital scale to weigh each bag. We also separately weighed the included stuff or compression sacks. Our 'Weight' performance category, however, is based solely on the weight of the bag under the assumption that most users will get an after-market compression sack that is lighter and more effective at compression.
Take ultralight principles to the extreme and it's possible to trim enough weight off your overnight pack to enjoy activities like climbing, skiing, or backpacking for weeks on end.
There is almost a 1.5-pound difference between the lightest and heaviest bags in this review: the Therm-a-Rest Hyperion 32 and the Kelty Cosmic 20, respectively. This difference may not sound like much, and perhaps for a single piece of gear, it's not. However, if you have the means and wherewithal to combine a 1.5-pound weight savings on your sleeping bag with comparable weight savings on your tent, sleeping pad, and cook kit, the difference becomes enormous.
The Hummingbird is our favorite backpacking sleeping bag for when we want to go light. Pair it with a backpacking tarp to really trim the weight of your overnight kit.
Premium ultralight bags, like our favorite Feather Friends Hummingbird UL, can thus become one piece in the puzzle that is cutting 10-15 pounds from your total load. Accomplishing this is expensive but can pay enormous dividends in back/knee health and overall enjoyment.
To sleep well, you have to be comfortable. Most people find this easy to achieve in a bed with a blanket and thermostat nearby. The task can be harder outdoors when you're at the mercy of mother nature and zipped inside an ill-fitting sack. Although some people can sleep like a log in any sleeping bag, many find the unfamiliar and inherently restrictive design to be disruptive. The former group can ignore this performance category, but the latter should devote special attention.
To evaluate comfort, we considered several factors: the dimensions and fit of a bag, the loft of the insulation, the feel of the interior fabric, and in some cases, the noisiness of the materials. Although being too cold or warm can obliviously affect how comfortable you are, we tried to evaluate the likelihood of this happening with our separate warmth and versatility metrics. A bag's comfort score is thus our best subjective judgment of its performance in terms of fit, loft, feel, and noisiness.
The symmetrical "comforter" on the Sierra Designs Backcountry Bed can be closed to seal heat in (top) or opened to let heat escape (bottom).
Three bags provided notably impressive comfort in three different ways that are worth discussing. The Sierra Designs Backcountry Bed is perhaps the most interesting of these. Its zipperless design incorporates a comforter-like flap that mimics the feel of an ordinary bed and blanket. This design, however, lacks a reliable closure mechanism, so it sometimes feels a bit drafty. Avoid this issue with the similarly comfortable Nemo Riff 30. It features a three-quarters-length zipper like a classic mummy bag, but is shaped like a broad hour-glass instead of a tapered sarcophagus. The bottom of the hour-glass gives side and tummy sleepers ample room to stretch their legs in any direction.
The lofty Western Mountaineering MegaLite (left), hourglass-shaped Nemo Riff (center), and zipperless Sierra Designs Backcountry Bed (right) all achieve their exceptional comfort in different ways.
While we enjoyed the Riff's innovative shape, its down is not particularly lofty, nor is its fabric exceptionally soft. The final standout in the comfort department, the Western Mountaineering MegaLite, addressed these deficiencies. Its 850+ fill power down and 12-denier ExtremeLite fabric team up to create a cozy cocoon of luxurious loft. Although it's among the most spacious models, it has a classic mummy shape that won't be appreciated by all.
Check out the difference between budget down and ultra-premium. The 850+ FP down of the Western Mountaineering MegaLite (right) lofts 6 inches upward, while the cheaper 650 FP down of the Klymit KSB 35 (left) lays nearly flat on the ground.
As these examples illustrate, a bag's comfort is inherently subjective, so it's essential to choose one that matches your preferences. Those that don't detest mummy bags will likely prefer the MegaLite's luxurious materials. Meanwhile, side sleepers may find the Riff's innovative shape superior. Finally, if zipping yourself inside a bag always made you feel claustrophobic, the Backcountry Bed may be your salvation.
Bags in their included stuff sacks. From left to right, top row: Therm-a-Rest Hyperion, Nemo Kyan, Nemo Rff, Mountain Hardwear Lamina, Feathered Friends Hummingbird, Feathered Friends Swallow. Bottom row: Western Mountaineering UltraLite, Western Mountaineeering MegaLite, Sierra Designs Cloud, Sierra Designs Backcountry Bed, Rab Mythic, Marmot Phase 20, REI Igneo.
The bigger your backpack, the further away its weight is from your center of gravity, the harder it is to carry, the more fatigued you get, the less fun you have. And sleeping bags occupy a significant portion of an overnight backpack. Therefore, getting a bag that compresses smaller can be an effective way to reduce the size, and burden, of your overall load.
All the bags we tested included a stuff or compression sack for storing inside your backpack. Many of these sacks, however, were unable to compress a sleeping bag fully. So to evaluate packed size, we used the same 11-liter Granite Gear compression sack to measure each bag's minimum compressed volume.
The Feathered Friends Swallow stuffed in an after-market compression sack (left) and the stuff sack that it comes with (right).
By and large, the compressed volumes we observed corresponded closely with the weight of each bag. A couple of exceptions were the Nemo Kyan 35, which compressed roughly 20% more than its weight would suggest, and the Marmot Phase 20 and Western Mountaineering UltraLite, which were 15% larger than comparably heavy bags.
The Nemo Kyan 35 (left) weighs nearly the same as the Western Mountaineering UltraLite 20 (center) but compresses a lot smaller. The UltraLite, however, is substantially warmer.
Although these discrepancies are worth noting, we consider all the bags we tested to be small, especially when compared to Best Budget Backpacking Sleeping Bags or the bags of yesteryear. Therefore, we don't think packed size is a great characteristic for distinguishing between the nicer backpacking sleeping bags. Depending on your budget, however, it may be worth checking if the bag you're thinking of getting includes a functional compression sack. If not, a quality after-market compression sack could set you back more money.
Related: The Best Budget Backpacking Sleeping Bags
Versatility speaks to how useful a piece of gear is for a variety of activities and conditions. For sleeping bags, we assessed it by considering the range of temperatures a bag is comfortable in, how well it performed if it got wet, and whether a bag does things besides keeping a single person warm when sleeping.
How comfortable a bag is in a range of temperatures is determined by its ability to insulate at lower temperatures and its ability to vent excess heat at higher temperatures. Draft collars and well-fitting hoods are both features that can boost a bag's cold-weather performance, such as those found on the Western Mountaineering UltraLite and REI Co-op Magma 30. Conversely, a long main zipper and accessory vents extend the Nemo Riff 30's performance on warmer nights.
The venting "gills" on the top of the Nemo Riff 30 with zippers closed and open.
Overall, the bags with three-quarters or full-length zippers seem to supply adequate venting options for most 3-season conditions. However, the shorter half-length zippers of the Rab Mythic 400, Therm-a-Rest Hyperion 32, and Sea to Summit Spark II can make sleeping in average summer temperatures far less pleasant.
The makers of all these bags call the zippers "full-length" but there is a noticeable difference between the Nemo Kyan (orange), Western Mountaineering UltraLite (blue), and Feathered Friends Swallow (red).
How well a bag performs when wet is primarily determined by its type of insulation. Down notoriously clumps and loses its ability to insulate if it gets wet. Synthetic fibers, in contrast, do not clump and can continue to supply up to 50% of their usual warmth when soaked. For this reason, synthetic bags, like the Nemo Kyan 35 and Mountain Hardwear Lamina 35, are better choices for particularly wet activities or environments.
The Nemo Kyan's synthetic insulation is ideal if you're worried about rain getting your sleeping bag wet.
Many manufacturers now market their down as hydrophobic because it receives a chemical treatment to improve water resistance. Claims about the performance benefits of these treatments seem to be overstated. In our testing, we observed little difference between down that was treated or untreated, so we didn't factor it into the versatility score. Interestingly, both of the top-performing bag makers, Western Mountaineering and Feathered Friends, do not use hydrophobic down due to concerns about the longevity of the chemical treatments and the possible harm that it might do to the water-resistant oils that high-quality down naturally contains.
We didn't identify any substantial difference in performance between hydrophobic and non-hydrophobic down. Both performed equally bad when wet. So if you're expecting rain, take every precautions to keep your down bag dry or use synthetic insulation instead.
The final aspect of versatility is how well a bag functions in non-traditional ways. We found bags with particularly long zippers, like the Feathered Friends Hummingbird UL 30 and Swallow 20 YF, could be shared as a quilt when fully unzipped, which is a nice bonus when eating breakfast on a cold morning or during an unplanned bivouac. The Sierra Designs bags, in contrast, lack insulation on the underside, which necessitates that they be used with a good sleeping pad. These designs, therefore, may not be a great choice if you're hoping to sleep in a hammock.
Bags with truly full-length zippers, like the Feathered Friends Swallow, can be zipped open to share as a quilt on really cold mornings.
Features and Design
Features and Design is a catch-all category to encompass the performance characteristics not addressed with other evaluation criteria. Features includes things like small stash pockets, sleeping pad attachment systems, and the quality of the bag's zipper, among other things. Design assesses the overall execution of the bag. Are all of its materials similarly durable? Do its warmth, weight, and dimensions make sense for its intended application?
One unique feature we like is the waterproof fabric on the footbox of the Nemo Riff 30, which ensures the bag's down insulation doesn't become saturated from brushing against condensation on a tent wall. We are also big fans of the full-length zippers on the Feathered Friends bags. Not only do they feature a Y-shaped, anti-snag slide, but there is an internal strip of plastic in the fabric next to the teeth that further reduces the chance of snagging.
The Feathered Friends bags that we tried feature a Y-shaped zipper slide and an internal strip of flexible plastic to prevent the zipper from snagging.
Another example of a particular design we like is the sleeping pad attachment system on the Therm-a-Rest Hyperion 32. Some people like attaching their sleeping bag to their pad to ensure they don't slide off. Most of our testers, however, find this to be unnecessary. They were thus delighted to discover that the Hyperion's attachment system is designed to be functional, but removable, allowing the user to decide if the extra weight is worth the benefits.
The straps on the underside of the Hyperion that you can use to secure it to a sleeping pad are also easy to remove if you'd rather save weight.
In contrast, the closure flap on the Sierra Designs Cloud 20 serves as an example of a design that didn't score highly. This bag has ample insulation and one of the lowest EN temperature ratings in the review (17°F). However, there is no reliable way to secure its asymmetrical, zipperless closure flap. Roll to you right, the bag opens, and chilly draft ruins your night.
There is a convenient elastic cord that keeps the Backcountry Bed's zipperless "comforter" (blue) in place, but the Cloud (red) doesn't have a similar way to secure its diagonal closure flap.
Another unfortunate sleeping bag flaw we've noticed concerns the main zippers without an open-ended closure. Most sleeping bag zippers have a pair of the interlocking pins found on one end which allow you to connect or disconnect the left and right sides of the zipper. Although easily overlooked, these tiny pins are necessary for restarting a zipper that gets misaligned. To save weight, however, some manufacturers have removed the pins, instead choosing to sew the ends of the zipper directly into the bags.
In our view, this design creates a huge durability problem. Even the best zipper will occasionally snag. When that happens, there is a decent chance the teeth will get misaligned or the slide will pop off one side. If that happens in the backcountry with the Sea to Summit Spark II or Thermarest Hyperion, prepare to shiver because you won't be able to zip the bag closed properly. Furthermore, fixing the zipper will likely require cutting it off the bag and then sewing it back on.
The pins at the bottom of most zippers (center) are necessary to get it restarted if the teeth become misaligned. Unfortunately, the Sea to Summit Spark II (left) and Thermarest Hyperion (right) both lack these important pins.
Marketing claims and a huge number of options combine to make sleeping bag shopping a tough undertaking. Our extensive testing process and thorough assessments aim to crack the code for traditional mummy bags. Depending on your preferences, however, you might be happier in an inexpensive car camping bag or a hoodless ultralight option.