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The Best Backpacking Sleeping Bags of 2020

Thursday April 23, 2020
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Over the last 10 years, we purchased and rigorously tested 99 of the best backpacking sleeping bags. Our 2020 review covers 17 of today's top models. Each underwent rigorous hands-on testing in the lab and backcountry, from snowy peaks in the Sierra Nevada to the sweltering desert of Death Valley. 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 comparing them 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: The Best Sleeping Bags for Women of 2020


Top 17 Product Ratings

Displaying 6 - 10 of 17

Best Overall Model


Western Mountaineering MegaLite


Editors' Choice Award

$470.00
(3% off)
at Amazon
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 fit
Luxurious loft
Great warmth-to-weight ratio
Pricey
Awkward hood closure

The MegaLite is our favorite backpacking sleeping bag because it performs exceptionally in all areas. Like other ultra-premium down bags, it offers an outstanding warmth-to-ratio in a bag that packs 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 limited 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 a high-end down bag are worth the exorbitant costs, especially when you factor in the outstanding longevity of their loft. The hard choice then 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

Best Value for Wet Conditions


NEMO Kyan 35


Best Buy Award

$199.95
at Amazon
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 functional compression sack
Doesn't live up to its 35°F rating
Weak loft

As a general rule, sleeping bags with synthetic insulation are larger and heavier than their down counterparts. But somebody forgot to tell the Nemo Kyan 35. It shocked us with its moderate weight and tiny packed size that matched several down bags at the same temperature rating. Also, its Primaloft Silver synthetic insulation is advantageous 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 of its 35°F temperature rating. In field tests, our testers felt this rating was overly aspirational. We thus only recommend the 35° version 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


Best Buy Award

$169.95
(6% off)
at REI
See It

54
OVERALL
SCORE
  • Warmth - 20% 6
  • Weight - 20% 3
  • Comfort - 20% 6
  • Packed Size - 15% 6
  • Versatility - 15% 6
  • Features & Design - 10% 6
Weight: 2.63 lbs | Packed Size: 8.7 liters
Very affordable
Decent weight and packed size
Suitable for backpacking
Burly materials
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'll likely sleep just as well inside the Cosmic while using the stack of money you saved as a decadent 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% down bags. With the money you save, however, you could invest in a lighter tent or more packable sleeping pad which would likely result in a lower overall weight or volume for your whole backcountry kit.

Read review: Kelty Cosmic 20

Best for Fast and Light Adventures


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
Exceptional warmth-to-weight ratio
Exceptional anti-snag zipper
Comfy hood
Expensive
Narrow fit
Noisy shell fabric

When saving weight is more important than anything else, 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 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.

We should mention that the Hummingbird UL achieves its low weight with especially 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 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 Backcountry
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
Possibly too warm

If you know you "sleep cold" or have plans for a colder trip in the spring or fall, the Western Mountaineering UltraLite may be the best bag for you. With its 17 ounces of 850+ fill power down and a legit draft collar, our testers think it was easily the warmest bag in the review. Also, its full-length zipper and horizontal baffle construction give you ample options for shedding heat and avoiding 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 a slightly less warm bag would be adequate for most 3-season travelers and provide additional benefits in terms of weight and packed size. 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


Top Pick Award

$219.73
(22% off)
at REI
See It

66
OVERALL
SCORE
  • Warmth - 20% 5
  • Weight - 20% 5
  • Comfort - 20% 9
  • Packed Size - 15% 8
  • Versatility - 15% 6
  • Features & Design - 10% 7
Weight: 2.10 lbs | Insulation: 700 Fill Power Dridown
Zipperless comforter-like closure
Roomy dimensions
Convenient foot vent
Great for tummy sleepers
Heavy for its warmth
Mediocre fill power
Drafty in cold weather

This bag lives up to its name by bringing the comfort of an ordinary bed to the backcountry. Its zipperless design features a blanket-like flap that you can fold open or closed to get your temperature just right. We also dig the foot vent for additional temperature control. The notably roomy dimensions also mimic the freedom of movement you enjoy in a regular bed, ensuring that you have plenty of space to stretch your legs or roll over.

The drawbacks to this exceptional comfort are the additional materials that its design require, which add weight and bulk to the overall bag. Its 35°F temperature rating also seems a little optimistic, so we suggest "cold sleepers" consider the 20° version or its cousin, 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 felt the design of traditional sleeping bags is 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.
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 ideal gear for backpacking, climbing, and ski trips. They have spent the better part of the last decade in the backcountry and 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 sifted through more than 100 of the most popular backpacking sleeping bags before selecting and purchasing the best 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 feet below to 14,000 feet above sea-level with nighttime lows between 10°F and 70°F.

Recording our thoughts during a field test with the Feathered Friends Hummingbird.
We stuffed all the sleeping bags we tested  including this Western Mountaineering UltraLite  into this Granite Gear 11-liter compression sack and then measured the dimensions to calculate compressed volume.
The authors of the our backpacking sleeping bag reviews with a pile of several million goose feathers.

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. And we're glad we did because they ended up being some of the highest-scoring models.

Related: How We Tested Backpacking Sleeping Bags

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.
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.

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 cut that weight, and you limit your options for venting excess heat. To analyze today's sleeping bags, we selected six important performance criteria that are often at odds with one another: warmth, weight, comfort, packed size, versatility, and features & design. We hope the result of this approach is that we're able to better evaluate overall performance.

Related: Buying Advice for Backpacking Sleeping Bags


Value


Although the price is not a consideration in our performance scores, we know it's a huge part of any purchasing decision. Sleeping bags come in a surprisingly broad range of prices for models that ostensibly serve the same purpose. After extensive testing, we can confidently say that these price differences generally reflect meaningful differences in performance.

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.
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 expensive 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 and Kelty Cosmic 20 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 models while approaching their high level of performance.

Related: The Best Budget Backpacking Sleeping Bags

Warmth


The warmth of a bag is largely a result 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 and fill power of the down it contains which corresponds to the quantity and quality of the insulation, respectively. This task is trickier with synthetics where the overwhelming number of different proprietary fibers makes comparison close to impossible. Further complicating matters is the design and fit of a bag which 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 developed to provide consistent temperature ratings between different companies. These EN ratings seem to be more accurate than the manufacturer-advertised temperature ratings of the past, but due to the added costs of testing, some of the best companies still do not have their bags tested. Also, the complicated details of the testing protocols can arbitrarily favor certain designs that may not reflect warmth in real-world conditions

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.
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. Each bag was slept in for at least three nights in a 48°F room. The performance was 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 a Nemo Kyan 35 in temperatures 10° above its 35°F rating.

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).
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).

Our warmth ratings are scaled so that a score of ten indicates a bag 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 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 the colder nights of spring and fall.

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.
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.

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. Customer reviews are filled with complaints about bags not living up to their ratings. In most cases, we believe these complaints are inaccurate, and the true culprit is an ineffective sleeping pad.

Related: The Best Backpacking Sleeping Pads of 2020

Related: The Best Backpacking Tents of 2020

Weight


In contrast to warmth, weight is easy to measure, and it is also is one of the most important considerations for human travel. 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 may harm versatility or comfort. We tested and measured all 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 separately from its included stuff or compression sack. Although we report the weight of stuff sacks, the 'Weight' performance category is based solely on the weight of the bag under the assumption that most users will use an aftermarket compression sack that is lighter and more effective at compression.

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.
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.

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 in the grand scheme, it's not. However, it amounts to a substantial 56% weight reduction. If you have the means and wherewithal to achieve similar weight reductions with your tent, sleeping pad, and cook kit, the overall weight savings can become enormous.

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.
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.

Premium ultralight bags, like our favorite Feather Friends Hummingbird UL, are thus 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.

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 harder outdoors when you're at the mercy of mother nature and zipped inside an ill-fitting sack. Although there are some people who 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 will 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).
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 achieves this with perhaps the most interesting approach. It's completely zipperless, utilizing a comforter-like flap to close that mimics the feel of an ordinary blanket. This design, however, lacks a reliable closure mechanism, so it sometimes feels 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 is shaped like a broad hour-glass instead of a tapered sarcophagus. The bottom of this hour-glass offers an extra foot of girth to give 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 to foot than an ordinary mummy bag. That leaves your legs with lots of luxurious room to stretch out.
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.

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, 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 for your torso, 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 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.
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 has always made you feel claustrophobic, the Backcountry Bed may be your salvation.

One aspect of comfort we didn't anticipate before testing was the noisiness of fabric. The lighter sleepers among our testers, however, quickly noticed the crinkly sound of some fabrics could disrupt their sleep. This issue was most noticeable with the Pertex Endurance fabric of the Feathered Friends Hummingbird UL. Anyone concerned about noise might consider avoiding this fabric. Fortunately for the Hummingbird, it can be ordered with Pertex Quantum fabric instead that is much quieter.

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.
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.

Packed Size


The bigger your backpack is the further its weight will be from your center of gravity, the harder it is to carry, the more fatigued you get, and ultimately, the less fun you will have. 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 include a stuff or compression sack for storing them inside your backpack. Many of these sacks, however, were unable to compress a sleeping bag fully. So 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 Mountaineering UltraLite 20 (center) but compresses a lot smaller. The UltraLite  however  is substantially warmer.
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.

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 Western Mountaineering UltraLite, which were 15% larger than comparably heavy bags.

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

Although these discrepancies are worth noting, we consider all the bags we tested to be small, especially when compared to Budget Backpacking Sleeping Bags or the behemoths of yesteryear. Therefore, we don't believe packed size is a great characteristic for distinguishing between today's nicest 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 will set you back more money.

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

Versatility


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 usable temperature range, 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 options for venting 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 usefulness to warmer nights.

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.
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.

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 on a warm summer night 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).
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 the 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. Some bags feature waterproof exterior fabric to try to prevent the insulation from getting wet at all. However, these fabrics add considerable wet and bulk along with the potential to trap your own body moisture inside. For these reasons, "waterproof" sleeping bags never became very popular and we chose to leave them out of this review.

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.
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.

Many manufacturers now market their down as hydrophobic because it receives a chemical treatment that's intended 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 don'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 have on the water-resistant oils that high-quality down naturally contains.

Bags with truly full-length zippers  like the Feathered Friends Swallow  can be zipped open to share as a quilt on really cold mornings.
Bags with truly full-length zippers, like the Feathered Friends Swallow, can be zipped open to share as a quilt on really cold mornings.

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 means they must 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.

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.
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.

Features and Design


"Features and Design" is a catch-all category to encompass the performance characteristics not addressed with our 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? Does 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 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 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.
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 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 be sure they don't slide off unexpectedly in the night. Most of our testers, however, find this to be wholly unnecessary. They were thus delighted to discover that the Hyperion's attachment system is designed to be functional, yet removable, allowing the user to decide if the extra weight is worth the benefits. We've tested plenty of sleeping pad attachment systems in the past that didn't come close to this nice of a design. Not all attachment systems are equal.

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.
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, and the bag usually opens, followed by a chilly draft to disrupt your slumber. We like the execution of the symmetrical blanket flap of the Sierra Designs Backcountry Bed much more.

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.
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 on several bags is a main zipper without an open-ended closure. Most sleeping bag zippers have a pair of the interlocking pins found on one end which allows you to connect and disconnect the left and right sides of the zipper. Although they're easily overlooked, these tiny pins are necessary for restarting a zipper that gets misaligned. To save weight some manufacturers have done away 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 versatility  but its sewn fully into the bag. That means if it gets misaligned there isn't a easy way to fix it.
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.

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 the teeth will get misaligned or the 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 it happens in the backcountry with the Sea to Summit Spark II or Thermarest Hyperion, prepare to shiver because you won't be able to restart it or zip the bag closed properly. Furthermore, fixing the zipper will likely require cutting it off the bag, getting the teeth aligned, and sewing it back together.

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.
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.

Conclusion


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 3-season backpacking sleeping bags. Depending on your activities you might be happier in a specialty ultralight option or inexpensive car-camping model.


Jack Cramer and Ian Nicholson