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Best Backpacking Sleeping Bag of 2021

Photo: Jack Cramer
Thursday March 4, 2021
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Over the last 10 years, we purchased and rigorously tested 101 of the best backpacking sleeping bags. Our 2021 review covers 17 of today's top models. Each bag underwent rigorous hands-on testing in the lab and backcountry, from snowy peaks in the Sierra Nevada to Death Valley's sweltering desert. Our experts considered every aspect of sleeping bag performance, including warmth, weight, comfort, and versatility. We know that you care about your sleeping bag options, and we've done our best to make selecting one an easy task. Whether you want the market's best overall bag or just a great deal, we'll lead you to the best product for your needs.

Related: Best Sleeping Bags for Women

Top 17 Product Ratings

Displaying 6 - 10 of 17
 
Awards  Best Buy Award    
Price $339 List$200 List$360.00 at Amazon
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$360 List$319.92 at Amazon
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Overall Score Sort Icon
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Pros Lightweight, small packed size, quality down, nice zipper, cozy fabricAwesome warmth-to-weight ratio for the price, very compressible, tons of venting options, nice compression sack includedGreat loft, high warmth-to-weight ratio, cozy hood, convenient interior stash pocketIncredibly lightweight, packs really small, removable sleeping pad attachment system, comes with a great compression sackPacks down really small, low weight, extra zipper for venting
Cons Moderate warmthNot as warm as its temp rating, no draft collar, uncertain durabilityExpensive, frustrating zipper, narrow fit, limited ventilation optionsExpensive, colder than its temp rating, narrow footbox, short one-way zipperNarrow footbox, cheap hood drawstring, fragile accessory zipper
Bottom Line Reasonable price for a great bagGreat warmth-to-weight ratio for an affordable priceA particularly lofty bag that's optimized for minimum weight, but not our favorite zipperSuper light and packable but colder than its 32° rating and not very versatileAn overly narrow footbox mires this otherwise great sleeping bag
Rating Categories REI Co-op Magma 30 NEMO Kyan 35 Marmot Phase 20 Therm-a-Rest Hyperion 32 Marmot Hydrogen
Warmth (20%)
5
3
8
4
6
Weight (20%)
9
7
8
10
8
Comfort (20%)
8
7
6
6
5
Packed Size (15%)
8
9
6
9
9
Versatility (15%)
6
9
7
4
6
Features & Design (10%)
6
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5
Specs REI Co-op Magma 30 NEMO Kyan 35 Marmot Phase 20 Therm-a-Rest... Marmot Hydrogen
Insulation 850 FP Down Synthetic - Primaloft Silver 850+ FP Down 900 FP Down 800+ FP Down
Compressed Volume (L) 6.7 L 6.6 L 8.6 L 6.6 L 6.8 L
Measured Bag Weight (Size Long) 1.39 lbs 1.89 lbs 1.74 lbs 1.14 lbs 1.73 lbs
Manufacturer claimed weight of size Regular (lbs) 1.24 lbs 1.69 lbs 1.46 lbs 1.00 lb 1.4 lbs
Compression/Stuff Sack Weight (oz) 0.4 oz 2.4 oz 1.0 oz 1.7 oz 0.8 oz
Hydrophobic down Yes N/A Yes Yes Yes
Manufacturer Temp Rating (F) 30 F 35 F 20 F 32 F 30 F
EN Temp Rating (Lower Limit, F) 30 F 35 F 18.5 F 32 F 23.4 F
Fill Weight (oz) 9.7 oz 12 oz 14.1 oz 9.2 oz 13 oz
Compression or stuff sack included? Stuff Compression Stuff Compression Stuff
Shell material Pertex ripstop nylon (15D) Ripstop nylon (20D) Ripstop nylon (10D) Ripstop nylon (10D) Pertex nylon ripstop (20D)
DWR? No Yes Yes Yes Yes
Liner material 15-denier ripstop nylon 30-denier nylon taffeta Pertex Quantum 10D 10D nylon ripstop 30D 100% nylon w/ DWR
Neck Baffle Yes No No Yes Yes
Small Organization Pocket No Yes Yes No Yes
Zipper 3/4-length / Side 3/4-length / Side 3/4-length / Side 1/2-length / Side 3/4-length / Side
Shoulder Girth (in) 63 62 60 57 61
Hip Girth (in) 57 57 58 49.5 56
Foot Girth (in) Not stated 46 45 43 Not stated

Best Overall Backpacking Sleeping Bag


Western Mountaineering MegaLite


Western Mountaineering MegaLite
Editors' Choice Award

$485 List
List Price
See It

80
OVERALL
SCORE
  • Warmth - 20% 8
  • Weight - 20% 8
  • Comfort - 20% 9
  • Packed Size - 15% 8
  • Versatility - 15% 7
  • Features & Design - 10% 7
Weight: 1.63 lbs | Fill Power: 850+ Goose Down
Warmer than its 30°F rating
Spacious dimensions
Luxurious loft
Excellent warmth-to-weight ratio
Pricey
Awkward hood closure

The MegaLite is our favorite backpacking sleeping bag because it performs exceptionally in every aspect. Like other ultra-premium bags with down insulation, it offers an outstanding warmth-to-weight ratio in a bag that packs down extremely small. But unlike other ultra-premium down bags we tried, it also features spacious interior dimensions that provide superior comfort no matter your sleeping style. For virtually any overnight backcountry activity, this is an excellent choice.

Our criticisms are few and minor: the hood closure is slightly awkward, and the zipper is good but not great. A more significant issue is the steep price that is likely to dissuade a lot of shoppers. However, we believe that a high-end down bag's considerable benefits are worth the additional cost for dedicated outdoor recreationists, especially if you factor in the superior longevity of premium down. The hard choice then is deciding between the MegaLite, our favorite bag for the average backpacker, and other top-performers such as the Feathered Friends Hummingbird UL or the Western Mountaineering UltraLite.

Read review: Western Mountaineering MegaLite

Best Bang for Your Buck


NEMO Kyan 35


NEMO Kyan 35
Best Buy Award

$200 List
List Price
See It

69
OVERALL
SCORE
  • Warmth - 20% 3
  • Weight - 20% 7
  • Comfort - 20% 7
  • Packed Size - 15% 9
  • Versatility - 15% 9
  • Features & Design - 10% 8
Weight: 1.89 lbs | Insulation: 12 oz of Primaloft Silver
Great price for its warmth-to-weight ratio
Packs super small
Retains significant warmth when wet
Includes a sturdy compression sack
Warmth falls short of the 35°F rating
Weak loft

As a general rule, sleeping bags with synthetic insulation are larger and heavier than their down counterparts. However, someone forgot to tell the Nemo Kyan 35. It shocked us with its moderate weight and tiny packed size that is on par with several down bags at the same temperature rating. The Primaloft Silver synthetic insulation is also advantageous for wet conditions because it retains a significant percentage of its warmth even when soaked. The cherry on top is the reasonable price tag.

The Kyan 35 achieves some of its low weight and small packed size due to the lower insulation requirements of its 35°F temperature rating. In our field tests, our team also felt that this bag doesn't quite live up to that rating. Therefore, we only recommend the 35° model for warmer three-season conditions. That said, many backpackers seeking a budget bag may trend toward warmer weather outings anyhow. As usual, consider your personal use requirements before deciding if the tradeoff is worth the savings. Despite its warmth deficiency, the Kyan 35 is an excellent bag at a low price.

Read review: Nemo Kyan 35

Best Bargain for a Backpacking Bag


REI Co-op Trailbreak 30


REI Co-op Trailbreak 30
Best Buy Award

$100 List
List Price
See It

52
OVERALL
SCORE
  • Warmth - 20% 5
  • Weight - 20% 3
  • Comfort - 20% 6
  • Packed Size - 15% 5
  • Versatility - 15% 7
  • Features & Design - 10% 6
Weight: 2.5 lbs | Packed Size: 9.8 liters
Rock bottom price
Acceptable specs
Simple design
Mediocre warmth
Heavy
Bulky
Finicky zipper
Annoying hood drawcords

We believe most backpackers will be happiest spending the extra money to receive the performance benefits of a premium sleeping bag. For folks unable to afford that choice, or for those just dipping their toes into the world of human-powered travel, the REI Co-op Trailbreak 30 might be worth considering. Its performance is several notches behind our favorite sleeping bags, but its price is several hundreds less, too. Although this bag's weight and packed size are subpar, we still think they meet the threshold to be acceptable for backpacking.

To enjoy the potential savings of the Trailbreak 30, you will have to accept some drawbacks. First among these drawbacks is a disappointing feature set that includes a frustrating zipper and annoying hood closure. At the same time, this bag also doesn't include an effective compression sack, or storage sack for that matter, so be sure to factor the cost of those items into your purchasing decision. Nevertheless, if you're desperate to go backpacking and unwilling to fork over the dough for a better performer, the Trailbreak 30 can get you out on the trails and savoring the great outdoors.

Read review: REI Co-op Trailbreak 30

Best for Fast and Light Adventures


Feathered Friends Hummingbird UL 30


Feathered Friends Hummingbird UL 30
Top Pick Award

$429.00
at Feathered Friends
See It

79
OVERALL
SCORE
  • Warmth - 20% 8
  • Weight - 20% 9
  • Comfort - 20% 7
  • Packed Size - 15% 8
  • Versatility - 15% 8
  • Features & Design - 10% 7
Weight: 1.45 lbs | Fill Power: 950+ Goose Down
Best loft in the review
Extraordinary warmth-to-weight ratio
Exceptional anti-snag zipper
Comfy hood
Expensive
Narrow fit
Noisy shell fabric

When saving weight is paramount, our favorite bag is the Hummingbird UL. Feathered Friends uses the highest fill power down we've tried (950+) to create a bag that is extraordinarily warm yet truly ultralight. Somehow this bag also manages to include a sturdy full-length zipper that's virtually immune to snagging. The same zipper provides ample venting options and the flexibility to share it as a quilt with a partner during a full-on bivouac.

It's worth noting that the Hummingbird UL achieves its low weight with notably 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 mummy bag that supplies an unparalleled warmth-to-weight ratio. There may be no better choice when the ounces really matter.

Read review: Feathered Friends Hummingbird UL 30

Best for Colder 3-Season Conditions


Western Mountaineering UltraLite


Western Mountaineering UltraLite
Top Pick Award

$510.00
at Amazon
See It

76
OVERALL
SCORE
  • Warmth - 20% 10
  • Weight - 20% 7
  • Comfort - 20% 7
  • Packed Size - 15% 6
  • Versatility - 15% 8
  • Features & Design - 10% 7
Weight: 1.86 lbs | Fill Power: 850+ Goose Down
Warmest bag in the review
Hefty draft collar
Sturdy full-length zipper
Continuous horizontal baffles
Bulky packed size
Super expensive
Too warm for many applications

If you know you "sleep cold" or have plans for colder trips in the spring or fall, the Western Mountaineering UltraLite is the bag for you. With 17 ounces of 850+ fill power down and a legit draft collar, our testers think it is easily the warmest bag in the review. At the same time, its full-length zipper and horizontal baffle construction give you ample options to shed heat and avoid overheating on hot summer nights. In the field, we could sleep comfortably in this bag across an expansive range of overnight temperatures from 10° to 55°F.

The primary drawback to this exceptional performance is a staggering price tag. We also believe that a less insulated bag would be adequate for most 3-season travelers while offering advantages in weight and packed size. Nevertheless, if you're looking for a fantastic bag that's assured to keep you toasty, the UltraLite is our favorite model.

Read review: Western Mountaineering UltraLite


Sleeping bags offer the highest warmth-to-weight ratio of any...
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.
Photo: Ian Nicholson

Why You Should Trust Us


Lead author Jack Cramer is an accomplished climber, member of the Yosemite Search and Rescue team, 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 ideal gear for backpacking, climbing, and ski trips. They've both spent the better part of the last decade in the backcountry developing the expertise to evaluate all sorts of outdoor gear. For this review, they consulted with Appalachian and Pacific Crest Trail thru-hikers, National Outdoor Leadership School alumni, manufacturer reps, and novice backpacker friends to ensure a diverse array of perspectives.

Our review team researched more than 100 of the most popular backpacking sleeping bags before purchasing 17 of the best to undergo extensive hands-on testing. We measured warmth, weight, and packed size in the lab. The remaining performance characteristics, including 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 were tested at elevations ranging from 150 feet below to 14,000 feet above sea-level with nighttime lows between 10°F and 70°F.

Click to enlarge
Click to enlarge
Click to enlarge

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 away free samples limits how many of their bags eventually get reviewed. Fortunately, OutdoorGearLab's policy to purchase every piece of gear that we review gives us the flexibility to include models from both makers in this comprehensive review. And we're glad we did because they ended up with some of the highest overall scores.

Related: How We Tested Backpacking Sleeping Bags

Cowboy camping under the stars is always a treat, but be wary of...
Cowboy camping under the stars is always a treat, but be wary of rain or dew with a down-filled bag like the Marmot Hydrogen.
Photo: Jack Cramer

Analysis and Test Results


Designing anything is a balancing act, and that's undoubtedly true for backpacking sleeping bags. Add insulation to make it warmer, and a bag can quickly grow too heavy. Cut that weight by shortening the zipper, and you reduce the ability to vent excess heat. It's a game of tradeoffs that varies by personal preference and planned usage. To evaluate today's top sleeping bags, we selected six performance areas that are usually at odds with one another: warmth, weight, comfort, packed size, versatility, and features & design. We hope that the result is a comprehensive analysis that accounts for every aspect of performance, so you can hone in on the ones that matter to you most.

Related: Buying Advice for Backpacking Sleeping Bags


Value


The price is a huge part of any purchasing decision. Sleeping bags come in a surprisingly broad range of prices for products that ostensibly serve the same purpose. After extensive testing, we can confidently say that the price differences do seem to reflect meaningful performance differences.

The Nemo Kyan impressed us with its outstanding performance and...
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.
Photo: Jack Cramer

Nothing came close to the Feathered Friends and Western Mountaineering bags in terms of absolute performance — they demonstrated clear superiority in overall design, build quality, and warmth-to-weight ratios. These expensive bags, however, would require most people to save up to afford them. For less than half the price of these premium bags, the Nemo Kyan 35 and REI Trailbreak 30 provide exceptional deals. Although they're a little heavier and bulkier on the trail, you will likely sleep just as well once you get them to camp. The REI Co-op Magma 30 is another bargain worth mentioning. Although it's not exactly inexpensive, it offers noticeable savings over the ultra-premium models while approaching their high performance.

Related: Best Budget Backpacking Sleeping Bag of 2021

Warmth


Sleeping bag warmth depends primarily on the quality and quantity of the insulation. For bags filled with down insulation, you can make a rough estimate of the warmth by considering the fill power and fill weight. Fill power is a measurement of the "loftiness" of the down fill and it corresponds to the amount of air a certain weight of down can trap. More trapped air means more trapped body heat. Sleeping bags usually contain down with a fill power between 500 and 900, with higher numbers indicating higher insulation ability. Fill weight is simply the amount of down inside the sleeping bag. Due to other design choices, two different sleeping bags with the same fill weight and fill power might not provide identical warmth, but they should be pretty close.


Estimating warmth is trickier with synthetic insulation because the wide array of proprietary fibers is overwhelming and it makes a comparison between manufacturers close to impossible. However, the fill weight should still provide a rough indication--a bag with 12 oz of synthetic insulation should be warmer than a bag with 8 oz.

In an attempt to standardize sleeping bag warmth measurement, the European Committee for Standardization developed the EN 13537 standard, which is a test designed to provide consistent temperature ratings for all sleeping bags. These EN ratings seem to be more accurate than the manufacturer-advertised temperature ratings of the past, but some of the best companies still don't get their bags tested due to substantial testing costs. Also, the testing protocols' peculiar details may arbitrarily favor certain designs while offering limited information on warmth under real-world conditions.

The EN comfort, lower limit, and extreme temperature ratings listed...
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.
Photo: Jack Cramer

Due to these issues, we chose to evaluate warmth using real human testers. Each bag was slept in for at least three nights in a 48°F room. Each bag's performance was assessed relative to the other bags in the review and their EN rating (if they had one). The difference between the warmest and coldest bags is 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 a Nemo Kyan 35 in temperatures 10° above its 35°F rating.

Despite the introduction of EN ratings, companies still chose the...
Despite the introduction of EN ratings, companies still chose the temp rating they market a bag at. Marmot leaves a nice buffer between the Hyrdogen's EN lower limit rating (23.4 F) and its marketed rating (30 F).
Photo: Jack Cramer

Further complicating warmth is the fit and design of a bag. A loose-fitting sleeping bag will leave extra interior space for your body to heat. On a cold night, this can make you feel colder. A bag that fits too tight, in contrast, can result in your body pressing against the insulation, compressing the loft, and reducing the insulation's ability to trap heat. For maximum warmth, it's best to size your bag so it fits snug but not tight. Other design features that can also affect warmth are zipper baffles and draft collars. Both features are additional pieces of insulation that are positioned to stop heat from escaping out the zipper and hood, respectively. Seek out these features if you want a bag to keep you toasty on the colder nights of spring and fall.

Our warmth ratings are scaled so that a score of ten indicates a bag with the highest level of warmth, and a score of one indicates the least. Importantly, this doesn't mean that a bag with a ten would be the best 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 best-suited for frosty nights during the shoulder seasons.

All bags are designed to be used with a good sleeping pad to...
All bags are designed to be used with a good sleeping pad to insulate you from the ground. Without one you'll be lucky to sleep at all near a sleeping bag's temperature rating.
Photo: Jack Cramer

Keep in mind that for your bag to perform up to its temperature rating, you need a quality sleeping pad and protection from the elements. It's not hard to find online complaints about bags not living up to their temp ratings. In most cases, however, we believe these complaints are mistaken, and the true culprit is an inadequate sleeping pad.

Related: Best Backpacking Sleeping Pad of 2021

Related: Best Backpacking Tent of 2021

Weight


Although warmth is hard to measure, it's easy to measure weight, and this is one of the most important metrics to consider when human-powered travel is involved. 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 they come with correspondingly high prices. Switching to a shorter zipper or a trimmer fit is a potential way to trim weight, but it will likely harm versatility or comfort. We tested and measured all the bags in this review in size Long to fit our lead tester.


To evaluate the weight, we used a digital scale to weigh each bag by itself, without any included stuff or compression sacks. Although we report the weight of stuff sacks individually, the 'Weight' performance category is based solely on the weight of the bag. This is under the assumption that most users will opt for an aftermarket compression sack that is more effective at compression and potentially also more lightweight.

The Hummingbird is our favorite backpacking sleeping bag for when we...
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.
Photo: Jack Cramer

There is a 2+ pound difference between the lightest and heaviest bags in this review: the Therm-a-Rest Hyperion 32 and the Nemo Forte, respectively. This difference may not sound like much, and in the grand scheme, it may not be. In a comparative sense, however, the Forte is 214% heavier. That's enormous. If you select similarly heavy gear for your entire overnight kit, the weight difference will quickly grow to double-digit pounds. That might be the difference between making it to camp before dark or turning back before your knees and back give out.

Take ultralight principles to the extreme and it's possible to trim...
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.
Photo: Jack Cramer

Premium ultralight bags, like our favorite Feather Friends Hummingbird UL, can thus serve as one piece in the puzzle that is cutting 10-15 pounds from your load. Accomplishing this is expensive but can pay dividends for your back/knee health and overall enjoyment in the outdoors.

Comfort


To sleep well, you have to be comfortable. For most people, this is a simple task in a bed with a blanket and thermostat nearby. The task can be a lot 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 environment to be disruptive. The former group can ignore our comfort evaluations. The latter should devote special attention.


To evaluate comfort, we considered several factors: the dimensions and fit of a bag, the loft or fluffiness of the insulation, the feel of the interior fabric, and in some cases, the noisiness of the materials. Although being too warm or cold can affect how comfortable you are, we assess the likelihood of that happening with our separate warmth and versatility metrics. Thus, a bag's comfort score is our best subjective judgment of its performance in terms of fit, loft, feel, and noisiness.

The Sierra Designs Cloud (red) uses a zipperless flap to seal you...
The Sierra Designs Cloud (red) uses a zipperless flap to seal you inside. This is great for reducing claustrophobia but it doesn't stay closed as reliably as a traditional zippered system.
Photo: Jack Cramer

Three bags provide impressive comfort in three different ways that are worth discussing. The Sierra Designs Cloud achieves its comfort with perhaps the most interesting approach. It's a completely zipperless bag that utilizes an overlapping diagonal flap to close. This flap supplies more freedom and less claustrophobia than a zippered closure. However, its zipperless closure is less secure, so it can feel a bit drafty. You can avoid this issue with the similarly comfortable Nemo Riff 30. It features a three-quarters-length zipper like a classic mummy bag, but it's shaped like a broad hour-glass rather than a tapered sarcophagus. The bottom of this hour-glass offers an extra 12 inches of girth compared to ordinary bags, which gives side and tummy sleepers ample room to stretch their legs in any direction.

The Nemo Riff 30, see here at the right, tapers far less from head...
The Nemo Riff 30, see here at the right, tapers far less from head to foot than an ordinary mummy bag. That leaves your legs with lots of luxurious room to stretch out.
Photo: Jack Cramer

While we enjoyed the Riff's innovative shape, its down insulation is not particularly lofty, nor is its fabric exceptionally soft. The final standout in the comfort department, the Western Mountaineering MegaLite, addresses these deficiencies. Its 850+ fill power down and 12-denier ExtremeLite fabric combine to create a cozy cocoon of luxurious loft. Although it's among the most spacious models in the torso dimensions, it has a classic mummy shape and narrow footbox that won't be appreciated by all.

Check out the difference between budget down and ultra-premium. The...
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.
Photo: Jack Cramer

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 the shape of a mummy bag 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 has always made you feel uneasy, the Cloud could be your salvation.

One aspect of comfort we failed to anticipate before testing was the noisiness of the fabric. The lightest sleepers among our testers, however, quickly noticed that some crinkly fabrics could disturb their sleep. This issue was most noticeable with the Pertex Endurance fabric of the Feathered Friends Hummingbird UL. Anyone concerned about noise should consider avoiding this fabric. Fortunately for the Hummingbird, it can also be ordered with Pertex Quantum fabric that is much quieter, but slightly heavier.

Bags in their included stuff sacks. We love it when the manufacturer...
Bags in their included stuff sacks. We love it when the manufacturer includes a compression stuff sack for the sleeping bag, adding value and reducing packed size.
Photo: Jack Cramer

Packed Size


The bigger your backpack is, the further away its weight will be from your center of gravity. This can make it more strenuous to carry, causing you to get more fatigued and ultimately making your time in the outdoors less fun. Sleeping bags usually occupy a significant portion of an overnight backpack. Therefore, getting a bag that compresses smaller is a good way to reduce the size and burden of your overall load.


All the bags we tested include a stuff or compression sack for storing them inside your backpack. Many of these sacks, however, are ineffective at compressing a sleeping bag fully. Therefore, to evaluate packed size fairly, we used the same 11-liter Granite Gear compression sack to measure each bag's minimum compressed volume.

The Nemo Kyan 35 (left) weighs nearly the same as the Western...
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.
Photo: Jack Cramer

By and large, the compressed volumes we observed corresponded closely with the weight of each bag. A couple of exceptions are the Nemo Kyan 35, which compresses roughly 20% smaller than its weight would suggest, and the Western Mountaineering UltraLite, which packs down 15% larger than comparable bags.

The Feathered Friends Swallow stuffed in an after-market compression...
The Feathered Friends Swallow stuffed in an after-market compression sack (left) and the stuff sack that it comes with (right).
Photo: Jack Cramer

Although these discrepancies are worth noting, we consider all the bags included in this review small, especially compared to Budget Backpacking Sleeping Bags or the behemoths of yesteryear. Therefore, we don't think packed size should be a crucial characteristic to distinguish between today's nicest backpacking sleeping bags. Depending on your budget, however, it may be worth checking whether the bag you're thinking of buying includes a functional compression sack. If not, a quality aftermarket compression sack is a relatively inexpensive option.

The Nemo Kyan's synthetic insulation is ideal if you're worried...
The Nemo Kyan's synthetic insulation is ideal if you're worried about rain getting your sleeping bag wet.
Photo: Jack Cramer

Versatility


Versatility is our assessment of how useful a piece of gear is for a variety of activities and conditions. For sleeping bags, we evaluated it by considering the usable temperature range, how well they perform if they get wet, and whether a bag can do things besides keeping a single person warm when sleeping.


How comfortable a bag stays across a range of temperatures is influenced by its ability to insulate when it's cold and shed excess heat when it's hot out. Draft collars and snug hoods, such as those found on the Western Mountaineering UltraLite and REI Co-op Magma 30, are both features that can boost a bag's cold-weather performance. Conversely, a long main zipper and accessory vents make the Nemo Riff 30 ideal for warmer nights.

The yellow strips on the top of the Nemo Riff are called "thermo...
The yellow strips on the top of the Nemo Riff are called "thermo gills." A small zipper cleverly allows you to spread out insulation for shedding heat on warm nights.
Photo: Jack Cramer

Overall, the bags with three-quarter or full-length zippers seem to supply adequate venting options for most 3-season conditions. Shorter half-length zippers, in contrast, such as those of the Rab Mythic 400, Therm-a-Rest Hyperion 32, and Sea to Summit Spark II, can make sleeping on a warm summer night far less pleasant.

The makers of all these bags call the zippers "full-length" but...
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).
Photo: Jack Cramer

How well a bag performs when wet is primarily determined by the type of insulation. Down feathers are notorious for clumping when they get wet, which severely reduces their ability to insulate. Synthetic fibers, in contrast, do not clump and can continue to supply up to 50% of their usual warmth even when soaked. For this reason, synthetic bags, like the Nemo Kyan 35 and Mountain Hardwear Lamina 35, are safer choices for particularly wet activities or environments. Some bags feature waterproof exterior fabric to try to prevent the insulation from getting wet at all. These fabrics, however, add considerable weight and bulk and increase the potential to trap your body moisture inside. For these reasons, "waterproof" sleeping bags never became very popular, and we have chosen to leave them out of this review.

Some bags, like the Riff 30, utilize waterproof fabric on the...
Some bags, like the Riff 30, utilize waterproof fabric on the footbox to prevent moisture on a snow cave or tent wall from soaking in.
Photo: Jack Cramer

A buzzword used to market many down bags recently is hydrophobic, which simply means that the down received a chemical treatment in an effort to make it more water-resistant. In our opinion, claims about the benefits of these treatments seem to be overstated. In our testing, we observed little difference between down that was treated or untreated, so we did not factor it into our versatility score. Interestingly, both top-performing bag makers, Western Mountaineering and Feathered Friends, do not use hydrophobic down. Instead, they express concern about the longevity of hydrophobic treatments and the possible harm it could do to the water-resistant oils that high-quality down naturally contains.

We didn't identify any substantial difference in performance between...
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.
Photo: Jack Cramer

The final aspect of versatility that we considered is how well a bag functions in non-standard ways. We noticed that bags with truly full-length zippers, like the Feathered Friends Swallow 20 YF or Hummingbird UL, can be shared as a quilt when completely unzipped. This is a nice bonus when eating breakfast on a cold morning or while trying to survive an unplanned bivouac. The Sierra Designs Cloud, in contrast, lacks a zipper or insulation on the underside of the bag. This means that it cannot be shared easily, and it must be used in conjunction with a good sleeping pad. For this reason, it's probably not a great choice for hammock sleeping.

When it comes to stash pockets, we prefer that they're located...
When it comes to stash pockets, we prefer that they're located inside rather than outside the bag. This ensures that the batteries in your electronics stay warm and holding a strong charge.
Photo: Jack Cramer

Features and Design


"Features and Design" is a catch-all category that encompasses the performance characteristics that are not addressed with our other evaluation criteria. "Features" include 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. This ensures that the bag's insulation doesn't get saturated from brushing against condensation on a tent wall. We're also big fans of the full-length zippers on the Feathered Friends bags. Not only do they feature a Y-shaped, anti-snag zipper slide, but there is an internal strip of plastic in the adjacent fabric to direct the fabric away from the zipper teeth and further reduce the chance of snagging.

The Feathered Friends bags that we tried feature a Y-shaped zipper...
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.
Photo: Jack Cramer

Another example of a 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, so they don't have to worry about sliding off their pad in the middle of the night. Most of our testers, however, think this is pretty unnecessary. We are thus delighted to see that the Hyperion's attachment system is designed to be functional yet removable, leaving the decision up to you whether the extra weight is worth the benefits. We've tested plenty of other sleeping pad attachment systems that don't offer a similar degree of adjustability. Not all attachment systems are equal.

The straps on the underside of the Hyperion that you can use to...
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.
Photo: Jack Cramer

Another flaw we've noticed on several sleeping bags is a main zipper with a fixed closure at both ends. Most sleeping bag zippers include a pair of the interlocking pins on one end that allow you to connect and disconnect the left and right sides of the zipper. Although they're easy to overlook, these tiny pins are necessary for restarting a zipper if it gets misaligned. For some inexplicable reason, a few manufacturers have done away with the pins, choosing instead to sew the ends of the zipper directly into the bags.

This auxiliary zipper on the Marmot Hydrogen boosts the bag's...
This auxiliary zipper on the Marmot Hydrogen boosts the bag's versatility, but its sewn fully into the bag. That means if it gets misaligned there isn't a easy way to fix it.
Photo: Jack Cramer

This design creates a huge durability problem. Even if you're incredibly careful, a zipper will occasionally snag. When that happens, there is always a chance that the teeth will get misaligned, or the zipper slide will pop off from one side. With most bags, it's not a problem; restart the slide at the pins, and it's fixed. But if misalignment occurs in the backcountry with the Sea to Summit Spark II or Therm-a-Rest Hyperion, prepare to shiver because you won't be able to restart the zipper or close the bag properly. Furthermore, fixing a misaligned zipper will likely require cutting it off the bag, realigning the teeth, and sewing it back together. We consider this durability issue so significant that we cannot recommend either of these bags.

The pins at the bottom of most zippers (center) are necessary to get...
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.
Photo: Jack Cramer

Conclusion


Deceptive marketing claims, a huge number of models, and preposterous prices combine to make sleeping bag shopping a daunting task. Our extensive testing process and thorough assessments aim to crack the code for three-season backpacking sleeping bags. Depending on your activities, you might be happier in a specialty ultralight option or inexpensive car-camping model. We hope this review has keyed you into the best model for your needs.

Jack Cramer and Ian Nicholson