There are loads of choices out there when it comes to winter down sleeping bags, and selecting the right one can be a serious investment. Well, rest easy, because we researched over 55 of the top bags out there and put 12 of the best to the side-by-side test, spending many cold nights out to find the best bag. We highlight which bag is the lightest, warmest, most comfortable, and the best overall. By stuffing and unstuffing, zipping and unzipping, shivering and even sweating, we've determined which bag is right for you on your next winter adventure. All so you don't have to scratch your head wondering if the $700 sack of bird feathers will keep you warm and happy on your next winter trip, or if you'll be sent plummeting down the financial bergschrund.
The Best Winter Down Sleeping Bags of 2018
We scoured the ends of the earth analyzing over 50 bags that are adept for use in cold temperatures. Our findings indicate that the Mountain Hardwear Phantom Torch 3 is best in the bunch, while the Nemo Sonic and Western Mountaineering Versalite take home Top Pick awards. The Best Buy remains the Rab Ascent 900, while the Kelty Cosmic 0, at $220, takes the cake as the Best Buy on a Tight Budget. New to the review this year, we've included the REI Co-Op Magma 10 and the Sea to Summit Talus III. A previous Editors' Choice winner, the Brooks Range Drift -10, is out of stock until late 2019, according to the manufacturer.
Best Overall Winter Bag
Mountain Hardwear Phantom Torch 3
Read review Mountain Hardwear Phantom Torch 3
Best Bang for the Buck
Rab Ascent 900
Need warmth but don't want to break the bank? Good thing there's the Rab Ascent 900. 31.7oz of 650 fill duck down kept our testers warm through the night. This bag is just as warm as other bags that are twice the price, but also a lot heavier. If you like to sleep on your side or your stomach, this bag has plenty of room for all kinds of slumber techniques. The Ascent 900 is a little heavy for long backpacking trips, but for a short trip or a base camp, this bag is a great budget option.
Read review Rab Ascent 900
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. Its heavy, and it doesn't pack down very small, but it will keep you warm, and we feel warmth is the most important feature when considering a winter bag. This bag also comes with some great features like a full-length draft tube and a draft collar. This bag weighs more than any other bag in our review, but it's still lighter than some of the synthetic alternatives. 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.
Read review Kelty Cosmic Down 0
Top Pick 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 2lbs 1oz, this bag has a great warmth-to-weight ratio and is awesome for spring ski tours and chilly climbing trips. The Versalite isn't as weather resistant as some of the heavier bags in this review, but it packs down smaller and weights less than every bag in its class, except for the REI Co-Op Magma. 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.
Read review Western Mountaineering Versalite
Top Pick 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. 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. If comfort, weather resistance, and warmth take priority over weight and packability, the Col is a perfect choice for your winter base camp.
Read review Marmot Col -20
Analysis and Test Results
A good sleeping bag is the single most important piece of gear you will carry on an overnight or multi-day trip into the wilderness. Think of it as your survival capsule in the wilderness. The ability to burrow inside a lofty down cocoon at the end of a cold day and get warm without a fire can turn an unforgiving snowy landscape into a winter sports paradise. 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. A good night sleep is essential for all the hiking, skiing, or climbing you plan on doing in the daytime. 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. With a multitude of expensive down bags out there, purchasing a good one can be more difficult than finding your way in a whiteout.
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 weight 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.
For 2018, 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 sleeping bag's warmth comes down to a combination of the volume or loft of its fill material and the cut or fit of the bag. A bag with more loft will keep you warmer because there will be more insulated air between you and the cold air outside. This insulated space allows for you to create a warm microclimate with your body heat! The cut or fit of the bag determines how much extra space will be inside the bag. 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, boots, headlamps, phones, and batteries. However, if there is more uninsulated space there is inside the bag, it is less thermally efficient. It will take longer to feel warm inside, and you will notice 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 44oz of 800 fill power down, and features a wide cut, with plenty of space for wear/storing extra layers. The Col takes home a perfect 10 out of 10 in this category. Our testers found they could even change clothes inside the bag. The tighter fitting The North Face Inferno -20 feels equally as warm with 36.4oz of 800 fill down because there is less uninsulated space. It also takes home a 10 out of 10 in the warmth metric.
Our Editors' Choice award-winning Mountain Hardwear Phantom Torch 3 (scoring an 8 out of 10) feels only a touch less warm and much lighter than the bags mentioned above and has less room than the Marmot Col but is wider than the similarly rated Snowbunting and Antelope. Finally, for those looking for maximum thermal efficiency, there is the Feathered Friends Snowbunting, the slimmest bag in our review, packing 25.3oz of 900 fill down into a 2lbs 13.6oz package. The Snowbunting also takes home a near perfect 9 out of 10 in this metric.
The Western Mountaineering Antelope MF, the Mountain Hardwear Phantom Torch 3, and our Top Pick for Comfort, the Nemo Sonic, are similarly rated and weighted bags, but the Phantom Torch 3 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 Sea to Summit Talus II, due to its high loft and a narrower cut.
Less expensive bags like our Best Buy Award Winning Rab Ascent 900, Sea To Summit Talus III or the Kelty Cosmic Down 0 can feel as warm as some of the higher end bags. The Rab Ascent 900 employs 31.7oz of 650 fill power duck 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. 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 REI Co-Op Magma 10, both scoring a perfect 10 out of 10. The Verslite boasts 20oz of 850 fill goose down and weighs in at 2lbs 1oz; 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 1lb 14oz but isn't as warm as the Versalite. The welterweight Western Mountaineering Antelope MF tips the scale at 2lbs 10oz, exactly the same as the Nemo Sonic, but the high-quality lightweight shell allocates more of that weight to insulation, so it feels warmer.
The warmest bags in our selection are also some of the heaviest. The Marmot Col -20 weighs 4.08 lbs, dedicating 21.3oz 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 Mountain Hardwear Phantom Torch 3 (2.74 lbs) cuts off a few ounces while still having a wide fit due to its light shell fabrics.
Midweight bags include the Feathered Friends Snowbunting (2lbs 13.6), the Rab Ascent 900 (3lbs 4.6oz), and the Big Agnes Storm King 0 (3lbs 6.7oz). The Kelty Cosmic Down is the least expensive bag and the heaviest, weighing 4lbs 1.5oz, almost the same as the Marmot Col -20, but nowhere near as warm or weather resistant.
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, but 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 the in the classic "can opener" position, due to the slight stretch in the middle. The Big Agnes Storm King 0 also scored high in the comfort metric due to its roomy interior and integrated pad design. Loved by some of our testers and hated by others, the Storm King features a pad sleeve that helps you stay on the pad throughout the night but makes it difficult to sit up while remaining inside the bag. The Rab Ascent is also quite comfortable, earning a perfect 10 out of 10, featuring extra room in the hips and foot box.
Both of the Western Mountaineering bags lost points in this metric due to their shallow hoods. Our testers generally preferred the slightly deeper, wider hood of the Mountain Hardwear Phantom Torch 3. The lowest scores in the comfort metric go to the Feathered Friends Snowbunting and the Kelty Cosmic Down 0. Both have shallow hoods and relatively narrow (but thermally efficient) cuts. Both bags scored a 6 out of 10, 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.
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.
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 predictably packs down the smallest, with the Nemo Sonic coming in at a close second. The Versalite 10 earned 10 out of 10 in the review, as did the equally packable REI Co-Op Magma 10. The Mountain Hardwear Phantom Torch 3 stuffs to a very small size, especially considering it's 29.9oz of down, due to its nearly translucent 10 denier shell fabric. It also has the best stuff sack (included).
Bags with a lower fill power down take up the most space. The Big Agnes Storm King 0 (650 fill) relies on its integrated pad for bottom insulation and packs down a little smaller than the Rab Ascent 900. The Kelty Cosmic Down 0 is 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.
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. 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. Bags with simple, effective features tended to score higher because they are less likely to break and make for a lighter, more reliable product.
Top scorers in this metric include the Marmot Col -20, and the Big Agnes Storm King 0, which all scored 9 out of 10s, and were pumping out the features. The Mountain Hardwear Phantom Torch 3, Nemo Sonic 0, and Rab Ascent 900 were all trailing closely behind, scoring above average 8 out of 10s.
It is essential that a winter bag can withstand condensation, snowmelt, and even the occasional rain shower, as the climate in the mountains is variable depending on elevation. If down gets wet it loses all its insulating properties and you'll have to cut your trip short, or worse. 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. 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 couldn't distinguish a difference between treated and untreated down, in part because the shell fabrics on many of the bags are so effective at repelling water that the down didn't get wet. Short of cutting into the bags to fully soak the down, there was no way to test the effectiveness of this 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.
The Big Agnes Storm King 0, Rab Ascent 900, 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). Even the lightweight Western Mountaineering bags and the Mountain Hardwear Phantom Torch 3 were impervious to light rain and condensation.
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 maximum loft. Read our Buying Advice article for pertinent info about how you can prolong the life of your down sleeping bag. The North Face Inferno -20, the Mountain Hardwear Phantom Torch 3, and the Rab Ascent 900 all include stuff sacks with compression straps, and the Mountain Hardwear compression sack is of notably good quality. 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 light, durable, and insulates well to complement a winter down bag.
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. Take a look at the Buying Advice article if you're still feeling uncertain.
— Matt Bento