Meeting winter head-on, our experts have tested 27 of the best winter down sleeping bags over 8 years. Purchasing 15 of the best and warmest, we spent months winter camping while sacrificing the comforts of a warm house. Tried and tested by ski patrollers, road trippers, and climbing dirtbags in the mountains through the winter months of California, we've got a pretty good handle on which bag is warm and which don't stack up. We meticulously evaluate key performance metrics to score each product. Our comprehensive review offers great recommendations for those seeking to save a buck and for those seeking the best performance on the market.
The Best Winter Down Sleeping Bags of 2020
Best Overall Winter Bag
Western Mountaineering Kodiak MF
This year's roundup brings us the Western Mountaineering Kodiak MF as our Editor's Choice Award winner. WM has been quietly churning out this bag to a devoted following of adventurers for years. Like the Antelope and the Versalite, this bag has a huge 3D draft tube and a snag-free zipper. What elevates it to Editors' Choice status is the super comfy 66" cut in shoulders, and its 30oz of 850 fill down, making our favorite balance of warmth, weight, and comfort for winter camping in the lower 48. The fact that testers could sleep on their stomach, side, or back without skipping a beat AND hold all of the gear that needs to be insulated all while staying comfortable really drove home the Editors' Choice award. It also packs down small!
Extra room in a sleeping bag is nice if you're going to be spending weeks at a time under the stars, but keep in mind that uninsulated space won't feel as warm as a tighter fitting bag. You can remedy this by stuffing your extra layers and jackets in the bag with you. Western Mountaineering bags are the gold standard, but they're expensive. Care for it, though, and this high-quality model could last decades of winters.
Read review Western Mountaineering Kodiak MF
Best Bang for the Buck
Therm-a-Rest Questar 0
The Thermarest Questar 0 offers comfort, compressibility, and a decent amount of warmth at a nice price. 650 fill power goose down won't break the bank, while its lightweight materials won't break your back. We're thrilled to see a winter sleeping bag at this price that manages to weigh in under three pounds. This bag also features hydrophobically treated down and a resilient shell fabric with a DWR treatment.
This isn't the warmest bag in our review, and the "0" in the name refers to the bag's transition rating, not its comfort rating, which is 14 degrees. The Transition EN rating refers to the temperature that the standard man will be "fighting against the cold but in thermal equilibrium". Basically, curled up but not shivering. If you're going to face temps hovering around 0, check out the Rab Neutrino 800. This bag isn't a screaming deal like the Questar, but it is much warmer and less expensive than many top performers.
Read review Thermarest Questar 0
Best Buy on a Tight Budget
Kelty Cosmic 0
The Kelty Cosmic Down 0 is great for the winter camper on the tightest of budgets. It weighs more than most bags, and it does not pack down as small as wed like, but it will keep you warm, and we feel warmth is the most important feature when considering a winter bag. After all, if you get the sleeping bag to the camping location and it isn't warm, who cares how light it is. This bag also comes with some great features like a full-length draft tube and a draft collar as well as a nice uninsulated stash pocket and a foot box flap to keep your toes warm.
This bag weighs more than any other bag in our review, a hefty 4.09 lbs, but it's much lighter than any other comparable synthetic sleeping bag when considering this bag is warm at 0F. If you're doing some car camping on your winter road trip, you don't have to let high prices stand in your way. Because this bag is heavy, we don't recommend it for alpine climbing or long backpacking trips. It is best suited for the occasional overnight and sleeping in colder temperatures at huts or in your car at a trailhead.
Read review Kelty Cosmic Down 0
Best for Lightweight Adventures
Western Mountaineering Versalite 10
The Western Mountaineering Versalite is our go-to bag for ultralight winter adventures. Weighing in at a scant 2 lbs 1 oz, this bag has a great warmth-to-weight ratio and is awesome for spring ski tours and chilly climbing trips. As with all the bags from Western Mountaineering, the Versalite has an awesome snag-free zipper, a lofty draft tube, and a warm draft collar. Paired with a down jacket, the versatile Versalite is a great choice for those who tend to sleep warm and want to cut weight.
The Versalite isn't as weather resistant as some of the heavier bags in this review, but it packs down smaller and weighs less than every bag in its class, except for the REI Co-Op Magma, which isn't as warm. If you're going to be facing temperatures consistently colder than the mid-teens and below, we'd suggest carrying a warmer or heavier bag, like the Western Mountaineering Antelope or the 0-degree Kodiak. If not, this bag is worthy of falling in love with.
Read review Western Mountaineering Versalite
Best for Comfort
NEMO Sonic 0
The Nemo Sonic gets our Top Pick For Comfort Award. The generously wide-cut gave our testers plenty of room to toss, turn, and sprawl inside this bag. Thermal vents allowed us to dial in just the right amount of warmth. Additionally, the deep hood, wide shoulder cut, and elastic foot box allowed our testers to change clothes while still inside the bag.
Our testers feel like the Sonic isn't as warm as some of the other 0 degree bags in our review, most notably the Western Mountaineering Kodiak MF. Because of the extra room, this bag isn't as thermally efficient as some of the tighter fitting bags, but if comfort is your top priority, this could be the bag you've been looking for.
Read review Nemo Sonic
Best For Expeditions
Marmot Col -20
The Marmot Col is a great bag for expeditions, where you'll likely spend days on end inside your sleeping bag, staying warm and waiting for good weather. This bag has plenty of room to store water bottles, boots, extra clothing, and anything else you don't want to freeze. This bag is so spacious that one of our testers found he could even read while remaining completely inside.
The Col weighs over 4 pounds and doesn't pack down as small as lighter bags in our review, so this isn't the best choice for long-distance human-powered activities. This is a better choice for folks getting around on a snowmobile, horse, or a dogsled. If comfort, weather resistance, and warmth take priority above weight and packability, the Col is a perfect choice for your winter base camp.
Read review Marmot Col -20
Why You Should Trust Us
This review is brought to us by Matt Bento and Jeff Rogers. Matt has spent more of his life in a sleeping bag than he cares to admit, working wilderness therapy, as a backpacking guide, and in his own backcountry climbing pursuits. He's used roomy bags for weeks of living out in the snow, and superlight bags for alpine missions in the Sierra. An ambitious skier, Jeff has many big ski descents under his belt, traveling everywhere from Alaska to Bolivia in the pursuit of big lines. These adventures take him deep into the backcountry, where he appreciates a sleeping back that is light and warm.
Discovering the best down bags began with scouring the market and looking at reviews of the most popular models to sort out the best for our tests. Then we purchased and evaluated the top candidates, scoring them with our metrics of warmth, weight, comfort, packed size, features, and weather resistance. After 100s of zipped zippers, packed backpacks, and plenty of chilly nights under the stars, we feel confident in our recommendations.
Analysis and Test Results
A key piece of gear in every person's overnight winter kit is their sleeping bag. Without it, it is very likely you will succumb to the extreme cold while trying to catch some sleep. Another great way to visualize your sleeping bag is that it's your "survival capsule." Say you were to rip a hole in your tent or break your leg far away from the nearest help, your sleeping bag will likely be the difference of getting rescued or becoming hypothermic waiting to be rescued. In most situations, you just need the ability to burrow inside a lofty down cocoon at the end of a cold day and get warm. Remember there is no other source of heat except for your body heat in most winter trips, having fires isn't always an option. Thankfully, modern down bags allow us to stay alive and even sleep comfortably in the coldest conditions with waterproof/breathable fabrics, hydrophobic down, and a variety of clever design strategies. The ability to not only fall asleep but also rest and recover adequately is key to enjoying any of the skiing, hiking or climbing you plan on doing during your trip. Shivering all night and surviving is one thing, but slumbering into a deep sleep to wake up refreshed is another!
Our review selection includes bags that will keep you warm and comfy in the parking lot of your favorite winter crag, as well as high-end, lightweight bags suited for climbing expeditions and backcountry ski tours. We brought back some tried-and-true favorites from our previous review and pitted them against a range of newcomers. Each bag was evaluated for its warmth, weight, comfort, packed size, features, and weather resistance.
A key part of purchasing a new winter bag is ensuring it fits within your budget constraints. While we don't factor value into a product's score in this review to remain objective about performance, we understand that this is a top consideration for most buyers. A big trade-off in this category is the quality of the down fill and the loft it provides. If you're paying less, the bag will generally weigh more and loft less, leading to a heavier pack and a less warm bag. But, to save a few hundred dollars (or more!), you might be willing to haul a tad more weight and sleep with your puffy on (which is more than likely with you on any winter trip). This is a personal choice, but one worth wrestling with. Also, consider the use case of this sleeping bag. Being as realistic as possible, how often are you sleeping in this bag? Once or twice a year? Ten times a year? 50 times a year? A top-dollar sleeping bag may not seem like much of an expense when you divide its price by 50 nights. Alternatively, if you're only using it a couple of times a year you don't NEED the highest-end materials and fabrics. The Therm-a-rest Questar 0 is great value, offering warmth under 3lbs, at a price you can swallow. If you're really strapped for cash, the Kelty Cosmic Down 0 provides good warmth at a great price, but is too heavy for most backcountry pursuits.
A sleeping bag's warmth stems from a few different factors. The fill power of the bag, the fill weight of the bag, and the cut of the bag most dramatically affect how warm a sleeping bag is. A bag with a high loft (a combination of fill weight and fill power) will keep you warmer because there will be more insulated air between you and the cold air outside. This insulated space allows you to create a warm microclimate with your body heat. The cut or fit of the bag determines the dimensions of the shoulder, hip, and foot box which can feel tight or roomy depending on a person's body shape. Extra space can be useful for accommodating extra layers you may want to wear, or items you want to keep warm with you through the night, like water bottles, radios, headlamps, phones, white gas, stoves, boot liners, and batteries. However, with the added airspace a larger cut bag provides, there is more uninsulated space inside the bag, and it is less thermally efficient. It will take longer to bring the sleeping bag from the ambient temperature to a suitable body heat temperature and feel warm inside. You will also have an easier time noticing any drafts that make it past the draft collar.
The warmest bags in our selection are the bags with the most loft and the most fill material. The Marmot Col -20 houses an impressive 44 oz of 800 fill power down, and features a wide cut, with plenty of space for wear/storing extra layers. Our testers found they could even change clothes inside the bag. The tighter fitting The North Face Inferno -20 feels just a touch less warm with 36.4 oz of 800 fill down. But this is due to a much more restrictive and therefore warmer and tighter cut.
Our Editors' Choice award-winning Western Mountaineering Kodiak MF feels less warm, while being much lighter than the bags mentioned above. It has less room than the Marmot Col but is significantly wider than the similarly rated Snowbunting and Antelope. It is a great option for those who value roominess, but also want to have plenty of insulation to keep them warm at 0F.
For those looking for maximum thermal efficiency, there is the Feathered Friends Snowbunting, one of the slimmest bags in our review. The Snowbunting packs 25.3 oz of 900 fill down into a 2.85 lbs package.
The Western Mountaineering Antelope MF, the Rab Neutrino 800, and our Top Pick for Comfort, the Nemo Sonic, are similarly rated and weighted bags, but the Rab Neutrino 800 and the Antelope feel warmer than the Nemo Sonic because they both have more down and narrower fits. The Western Mountaineering Versalite, conservatively rated to 10 degrees, is the lightest bag in our review but is still warmer than the heavier Nemo Sonic and the REI Co-op Magma 10, due to its high loft and a narrower cut.
Less expensive bags like the Best Buy Award Winning Thermarest Questar, Rab Ascent 900, the Kelty Cosmic Down 0 can feel as warm as some of the higher-end bags. The Thermarest Questar employs 29 oz of 650 fill power down to a achieve a warmth rating similar to the much lighter and more expensive Western Mountaineering Versalite. The good news is that you can sleep out in the lower temps at a lower price. The Kelty Cosmic Down 0 is as warm and lofty as the Rab Ascent 900, but you'll pay with your legs, back, and the space in your pack.
A sleeping bag's total weight is a function of its fill material and the weight of its shell fabrics. In our tests, there are two important indicators, the fill weight, and the weight of the rest of the bag. You can compare this ratio against other bags to see how warm for the weight the bag is. A bag with higher quality down (800 or more) can achieve a lower temperature rating at a lower weight. High-tech shell fabrics allow for weather resistance and durability, even in light, 12 denier shells. Light is right if you're going the distance! But it's usually very expensive.
The lightest bags in this review are the Western Mountaineering Versalite with its super thin 12 denier Extremelite shell, and the sub-two-pound REI Co-Op Magma 10. The Versalite boasts 20 oz of 850 fill goose down and weighs in at 2 lbs 1 oz; it has an excellent warmth-to-weight ratio but isn't as weather-resistant as the heavier Feathered Friends Snowbunting. The Magma 10 weighs a scant 1 lb 14 oz but isn't as warm as the Versalite. The welterweight Western Mountaineering Antelope MF tips the scale at 2 lbs 10 oz, exactly the same as the Nemo Sonic, but the high-quality lightweight shell allocates more of that weight to insulation, so it feels warmer. It's important to also look at what kind of environment the bag will be experiencing. Maybe it makes sense to get a more weather resistant shell if you often face damp climates during your winter excursions.
The warmest bags in our selection are also some of the heaviest. The Marmot Col -20 weighs 4.08 lbs, dedicating 21.3 oz to its tough, highly weather-resistant 30 denier Pertex shell fabric, while The North Face Inferno -20 (3.44 lbs) shaves off the ounces with a lighter shell and a smaller cut. The Western Mountaineering Kodiak MF (2.85 lbs) cuts off a few ounces while still having a wide fit and great features due to its light shell fabrics. In our experience all of these bags proved to be very weather resistant, with the marmot col being waterproof, it was a struggle to force water into the baffles!
Midweight bags include the Feathered Friends Snowbunting (2 lbs 13.6) and the Rab Ascent 900 (3 lbs 4.6 oz). The Kelty Cosmic Down is the least expensive bag and the heaviest, weighing 4 lbs 1.5 oz, almost the same as the Marmot Col -20, but not even close in terms of warmth and weather resistance.
We determine comfort based on the feel of the bag against our skin, how the hood and draft collar fit, and most importantly, how much space is in the bag. Sleeping bags with a wider cut generally received higher comfort scores. If you sleep exclusively on your back, a wide cut isn't too much of a concern. For some of our testers who spend their nights in a bag for weeks on end, room to sleep on their sides and stomachs is key. The price of comfort? Extra fabric equating to extra weight and less space in your backpack. Consider how well you perform after a poor night of sleep and you may decide the extra weight is worth it.
The Nemo Sonic wins our Top Pick for Comfort because it has the widest cut of all the bags; it employs a 20 denier ripstop fabric to keep the weight down from all that extra girth. Our testers found they could sleep comfortably in this bag in any position, even in the classic "can opener" position, due to the slight stretch in the middle. The Thermarest Questar 0 is also quite comfortable, featuring extra room in the hips and foot box.
The Western Mountaineering Versalite and the Antelope lost points in this metric due to their shallow hoods. Our testers generally preferred the slightly deeper hood of the Kodiak with drawstrings for the hood and the draft collar. The lower scores in the comfort metric go to the Feathered Friends Snowbunting and the Kelty Cosmic Down 0. The Snowbunting and the Cosmic Down have shallow hoods and relatively narrow (but thermally efficient) cuts. These bags didn't score very high here but are by no means uncomfortable - simply average. Again, if you primarily sleep on your back, the width isn't so important. Additionally, if you're interested in the Snowbunting for alpine and big wall climbing, you'll likely be on your back anyway, sleeping on a narrow ledge or nestled among the rocks. Conversely, if you are spending weeks climbing Denali, or weeks camping in remote and cold locations, a thermally efficient cut can get tight quickly. With the added amount of items needed to sleep with and the overall longevity of time spent in your sleeping bag, it makes sense to go with a wider cut like the Kodiak or Marmot Col.
Ski touring can be a gear-intensive activity, and pack space is a premium once you've accounted for a shovel, probe, food, water, layers, and a tent. Ditto for alpine climbing, when you may find your pack overflowing with ropes and cams. Higher quality materials are critical for increased packability. To assess the packed size, we crammed each bag into our Sea to Summit compression sack and pulled down as hard as we could on the compression straps. We then got an accurate idea of how each sleeping bag compressed in the same stuff sack, as well as how they compressed in their own stuff sacks when the manufacturer included them.
Much to our surprise and delight, each bag fit inside the compression sack, even the hulking Marmot Col, which looks huge when lofted in its storage sack. The ultra-light Western Mountaineering Versalite and REI Co-Op Magma 10 predictably compress the most. We found it easiest to compress the bags by sitting on them once they were in the stuff sack, you can then rotate the compression sack and tighten each strap. The Editors' Choice Award-winning Western Mountaineering Kodiak MF packs down to a backpack-friendly size, even though it's one of the wider and warmer bags in the review. This is why we love the Kodiak so much, a ton of loft, and room with a manageable packing size.
Bags with a lower fill power down take up the most space. The Kelty Cosmic Down 0 one of the least packable, taking up more room than the Marmot Col and The North Face Inferno -20.
Features are a subjective, multifaceted metric, comparing aspects universal to all the bags such as draft tubes, hoods, and zippers, while also factoring in characteristics unique only to certain bags. Some bags had stash pockets, which are useful for storing batteries or a watch but also can be annoying if you roll over on them. Some sleeping bags also had two zippers so you could sit up while still inside the bag. Other bags had "gills" to allow you to vent at the base of the climb where you may not encounter conditions even close to 0F. All of these features were considered when scoring a bag.
The Nemo Sonic has a ventilation system employing two zippered gills on the top of the bag, so you can cool off when using the bag in warmer weather. We feel this is an interesting feature but do not like the fact that if the zipper breaks, you are now in a 20F bag regardless of how cold the night time low is. The Western Mountaineering bags are a standout for their awesome snag-free zippers, while the Nemo Sonic's zippers constantly snagged on its double draft tubes. The Thermarest Questar 0 has removable elastic straps for securing it to a sleeping bag, a feature a few of our testers find useful. It also features a down-insulated flap in the toe box to take up some dead space and increase warmth, but you can do the same thing with a jacket or an extra layer, so we don't think it's a game-changer, but it did add a bit of warmth to the toe box. A few bags had a small pocket inside the bag for keeping small items accessible and items with batteries warm. Bags with simple, effective features scored higher because features are great, but when they break they can cause problems, and they also add weight. So if the feature set was well thought out, reliable, and didn't add significant weight to the bag, those scored the highest.
The top scorer in this metric is the Marmot Col -20, pumping out the features. The Nemo Sonic 0 and Rab Ascent 900 were all trailing closely behind.
Due to the variety of conditions that can be encountered on a climb, a sleeping bag must be able to withstand wet weather. Condensation from tents, frost from your breath freezing on the inside and even a light rain shower are all realities your sleeping bag might face on a multi-day climb. When down gets wet, it loses its loft because the down clusters can no longer trap air, this results in a total loss of insulating properties.
Alternatively, If a bag can withstand the elements well enough on its own, you get a bonus weight savings since you don't have to bring along a bivy sack or a tent. A sleeping bag's weather resisting abilities boil down to shell fabrics. The variety of shell fabrics on the market make some down sleeping bags suitable for use out in the open, others made for the shelter of a tent. Some of the bags feature specially treated hydrophobic down.
The manufacturers claim hydrophobic down absorbs less water and maintains its loft better, and dries out faster than untreated down. Our testing team could easily distinguish a difference between treated and untreated down in some of the sleeping bags with a more delicate face fabric. We found that the sleeping bags with a thick waterproof shell didn't seem to need hydrophobic down as it was hard to get the down inside the bag wet at all, short of sticking the garden hose INSIDE the bag. This style of testing was a necessity, as there was no other way we could force water into some of the down bags. They were just that waterproof. The Thermarest Questar 0, the Rab Neutrino 800, and the Rab Ascent 900 all feature down with a hydrophobic treatment.
The Marmot Col -20 is king when it comes to combating the adverse weather. Its burly, waterproof shell absorbed zero water, even in our submersion test. The Feathered Friends Snowbunting and The North Face Inferno -20 fall in right behind the Marmot Col. All of these contenders kept our testers warm and dry in light rain. And something to note, none of these bags contain hydrophobic down! The best bags for cowboy camping just have excellent shell fabrics.
The Rab Ascent 900, the Rab Neutrino 800, and the Nemo Sonic resisted the rain well, but all absorbed small amounts of water in the submersion test (just don't jump in the lake with your sleeping bag and you'll be fine). And if you do jump in the lake, make sure you are wearing the Marmot Col -20F! Even the lightweight Western Mountaineering bags were impervious to light rain and condensation. We want to stress how high tech these fabrics are nowadays and that you don't need a full membrane for most applications.
Only the Kelty Cosmic Down 0 absorbed enough rain to soak through to our testers. If you decide to purchase this warm, budget-friendly bag, make sure you've got an effective way to keep it dry, like a tent, or the back of your car.
A stuff sack and a storage sack are included with each of the bags in this category, with the exception of the Kelty Cosmic Down 0, which only comes with a stuff sack. The Western Mountaineering bags have the largest storage sacks so you can store them at the maximum loft. The North Face Inferno -20 and the Rab Ascent 900 both include stuff sacks with compression straps, and the Rab Neutrino 800 comes with a dry bag. Additionally, some sleeping bags come with a compression sack, which is useful for getting the smallest form factor out of your sleeping bag. Alternatively, in some conditions stuffing the bag directly into the backpack can yield the best results. Be sure to purchase a quality pad that will keep your body warmth in. All the expensive, high-quality down is useless if it's compressed underneath your body, with only a thin shell layer between you and the frozen ground. You'll need a pad that's light, durable, and insulates well to complement a winter down bag. Look for an r-value of at least 5, which can be achieved with a foam pad underneath and inflatable pad. Alternatively, there are some high-end sleeping pads that do not require the addition of foam underneath.
We hope we've unraveled some of the mysteries around selecting the best cold weather down bag to suit your specific needs. While a down bag may seem like a huge financial investment, it will keep you warm and cozy for years if properly cared for, and nothing beats a good night's sleep under the stars on a long winter's night.
— Matt Bento and Jeff Rogers