The most important attributes of a sleeping bag for winter camping and backpacking are warm insulation, compressibility, low weight, and ample interior space to store gear and water so it doesn’t freeze overnight. Cost is also a factor, although a good winter sleeping bag will last fifteen years or more if maintained and stored properly. For winter backpacking and other mobile pursuits such as backcountry skiing and ski mountaineering, we recommend you get a down-insulated winter sleeping bag because it packs up much smaller and is much lighter weight.
Temperature Rating: Winter sleeping bags come with temperature ratings that indicate the lowest temperature at which the bag will keep you warm. Look for a bag with a temperature rating appropriate for the coldest conditions you expect to encounter. It's a good idea to choose a bag rated for temperatures lower than what you expect to encounter to provide a safety buffer.
Insulation Type:
Fill Power: If you're going with a down sleeping bag, pay attention to the fill power. Higher fill power indicates higher quality down and better insulation. It also affects the packability and weight of the bag.
Fit and Size: Make sure the sleeping bag is spacious enough to allow for movement while inside but not so large that your body heat can't warm the air inside effectively. You don't want too much empty space as it might lead to cold spots.
Shape:
Weight and Packability: Consider the weight and compressibility of the sleeping bag, especially if you're going on a backpacking trip. Down bags are generally lighter and more compressible than synthetic ones.
Features:
Brand and Quality: Choose reputable brands known for producing quality outdoor gear. Read reviews and check for warranties.
Try Before You Buy: If possible, try the sleeping bag in-store to see how it fits and whether you find it comfortable.
Layering: Remember that your clothing layers also play a role in keeping you warm. Wearing thermal layers and a hat can significantly enhance the warmth provided by the sleeping bag.
Price: Quality winter sleeping bags can be expensive, but they are an investment in your comfort and safety. Consider your budget and balance it with the features you need.
Remember that individual comfort levels can vary, so it's a good idea to test the sleeping bag in controlled conditions before embarking on a serious winter trip.
A mummy sleeping bag is warmer and more comfortable than an ultralight down quilt under 20 degrees Fahrenheit. While quilts are popular for warm weather use, mummy bags are far less drafty when the mercury drops below 20 degrees. They also provide a warm overnight space where you can keep water, filters, and footwear overnight to prevent them from freezing. This is harder to do with an ultralight quilt, which is usually shorter and sized narrow to save weight. Sleeping in temperatures below freezing definitely changes your behavior and requires a different skillset and gear list than regular three-season camping or backpacking in warmer weather.
Down insulation is more compressible and warmer by weight than synthetic insulation. How much warmer? The best synthetic insulation is only equivalent to 600 fill power down. What about moisture accumulation inside the bag? If you’re just going out for one night or a few nights in zero-degree weather, it’s unlikely that you’ll perspire enough to significantly reduce the insulation value of a down bag. It’s a very different story if you’re on an expedition where you’re sleeping out in -40 degree weather every night for weeks on end. Even then, most mountaineering guides and explorers still opt for down-filled sleeping bags over synthetic ones because they’re warmer, pack up much smaller, and are much lighter weight to carry. You can also dry out a sleeping bag during a trip in the sun to rid of it any extra moisture. People do it all the time.
There’s no such thing as waterproof down. While so-called down waterproofing treatments allow down to dry faster if it gets damp from perspiration, most premium sleeping bag makers won’t use it because it reduces the perceived insulation value of 800, 850, 900, ad 950 fill power goose down.
What is the best sleeping bag temperature rating to get for winter backpacking? While there are bound to be regional differences, a zero-degree sleeping bag is usually a good baseline temperature to aim for because you can easily make it warmer by 20 degrees by wearing insulated clothes or by using a sleeping bag liner, which can save you a chunk of money. A zero-degree bag can also be used in warmer temps up to about 20-30 degrees by cracking open the zipper or loosening up the hood and venting it if you’re too warm. The weight and packability of a zero-degree sleeping bag is also pretty reasonable compared to a minus 20-degree bag or minus 40-degree bag and usually doesn’t require the purchase of a larger backpack to carry.
If you plan to do any winter backpacking, you’re going to want a down-insulated sleeping bag because it’s the warmest insulation available by weight. It compresses very well, making it very packable. Aim for down fill powers of 800, 850, or 900: the higher the better. Higher fill power down traps more warmth by weight than lower fill power down. People often wonder whether goose down is better than duck down. All down is graded the same way, in a species-independent manner. In other words 800 fill power goose down is as good as 800 fill power duck down, only more expensive because there’s a smaller supply.
It is common to sleep with boot liners or boots, water bottles, and other items, like water filters, that should not freeze overnight. This means you’ll want some extra space in a cold-weather sleeping bag to store the gear while still maintaining your personal comfort. In addition to added shoulder, hip, and foot width, some people get a longer sleeping bag so they can store gear below their feet. Winter nights are long and it pays to be comfortable, especially if you have to sleep with cold, damp boots and water bottles.
Most zero-degree winter sleeping bags are unisex. The one exception to this is Featured Friends which makes seven women’s specific sleeping bags by our last count including 0, -10, and -25 degree winter sleeping bags.
Winter sleeping bags should have a draft collar, zipper draft tubes, and snag-free zippers at a minimum. Partial length zippers, continuous baffles, vents, and even water-resistant down are all nice-to-haves, but you can get by without them to save on cost or because they’re not strictly necessary.
Most winter sleeping bags have draft collars and I consider it a cold-weather essential. A draft collar is a tube of insulation that drapes over your chest and neck and seals in the bag’s warmth. Without it, the warm air inside the bag will rush out around your neck when you move around inside. The simplest draft collar is a down tube that covers the front of your chest. Higher-end bags add a second draft collar around the back of your shoulders and neck and provide additional controls, so you can tighten or loosen it.
Draft tubes are down-filled tubes of fabric that cover up the side zipper so your legs don’t come in contact with it (because it’s cold). They also prevent cold air from leaking into the bag through the needle holes that are created when sewing the zipper to the bag. Most winter bags have at least one zipper draft tube, although some have two, both top and bottom, that fall into place when you zip up your bag.
Snag-free zippers prevent the side zipper’s teeth from tearing the shell fabric of your bag and spilling its insulation. The zipper is usually bordered by stiff fabric tape, to keep it away from the down baffles and prevent it from getting snagged on the bag’s outer shell.
Water-resistant down is a nice to have, not a must-have in a winter sleeping bag. The truth is most people can keep their sleeping bags dry. If you notice moisture on the outside of your sleeping bag in the morning, it doesn’t mean that the down inside is wet. Simply drape it over your tent in the sun while you eat breakfast and it will dry in no time.
Continuous baffles usually run horizontally across a bag. They allow you to shake the down in the baffles and move it to a different location. For example, if you’re too warm, you could shake the down so it fell down the sides of the bag, rather than keep it on your chest. While continuous baffles let you customize the distribution of down for different needs, many people prefer baffles that keep the down in one place reliably and permanently. It’s one less thing to worry about.
Partial length zippers are often used as a weight-saving feature, however, they can reduce use across a wider temperature range by limiting your venting options.
Vents like NEMO’s Thermogills can increase the temperature range of a sleeping bag, but they’re just one way of accomplishing this goal.
Mummy bags tend to be lighter weight because they’re form-fitting, making them better for winter backpacking when you want a lightweight, compressible sleeping bag. Rectangular sleeping bags can be just as warm, but they’re more appropriate for winter camping, not backpacking, because they’re not as form-fitting, they’re heavier, and have less efficient hoods to keep your head warm.
It really depends on how cold you want to go. Most people switch from quilts to mummy sleeping bags at about 20 degrees Fahrenheit because sleeping bags are much better at blocking cold drafts than quilt-pad attachment straps. A quilt can certainly work down to 0 degrees if you augment it with a down hood (effectively replicating a mummy bag hood and draft collar) to keep your head, neck, and upper chest warm. Below zero, you can try stacking quilts but I highly recommend testing out this strategy at home before trying it someplace where it counts.
If you’re interested in winter backpacking, your best bet is to get a down sleeping bag with the highest down fill power (see below) you can afford because it is ounce-for-ounce lighter weight and more compressible than a winter sleeping bag filled with synthetic insulation. Winter backpacking gear is very heavy when you add up the weight of insulated boots, a high-capacity backpack, a four-season tent, winter sleeping pad(s), a liquid fuel stove, fuel, snowshoes, crampons, etc. so it really does pay to save as much weight and pack space as you can by using the lightest and smallest winter sleeping bag that will keep you warm.
So-called waterproof down isn’t actually waterproof, but water-resistant. If you dunk it in water, it will fail to insulate, although it will dry faster than untreated down. Therefore, if you plan on sleeping in snow caves or out in the open in a bivy sack, waterproof down is probably a better option since the down will dry faster if the fabric shell of your bag gets wet. If you’re sleeping in a cozy tent with a waterproof floor, it probably doesn’t matter that much, except if you’re on a multi-day trip where the accumulation of perspiration passing through your insulation and out the breathable shell of your sleeping bag can accumulate in the down, degrading its loft and ability to retain warmth. Waterproof down would be better in those circumstances.
Down consists of fluffy filaments that are a lot like human hair. A single ounce of average quality down contains about 2 million of these filaments which interlock to keep warm air in and cold air out. This layer is very springy so you can scrunch it up by compressing it, but it will spring back into shape almost immediately. Fill power measures the lofting power of goose down which is its ability to trap air. To measure fill power, one ounce of down is compressed in a small glass cylinder. When the weight is removed, the down’s ability to spring back can be measured. Down with a higher fill power rating is more resilient to compression, lofts better, and can trap more air. Besides being warmer, this also means that sleeping bags or parkas with higher fill ratings require less insulation by weight to provide the same level of warmth as an item made with lower quality down.
No. Fill power is measured the same way across different animals and species. In other words, 750 fill power goose down provides the same level of insulation as 750 fill power duck down.
Yes. The higher the fill power, the more expensive it will be. Prices have dropped in recent years however since there is a worldwide surplus of down, the higher fill powers remain the most expensive.
The lightest weight, most compressible winter sleeping bags are insulated with 800, 850, 900, or 950 fill power down. A 950 fill-power down bag is top of the line.
While warm weather sleeping bag ratings have become much more objective in recent years with the adoption of international temperature rating standards and third-party testing, the same can’t be said about winter sleeping bag temperature ratings. While the EN and ISO temperature ratings published for warm weather sleeping bags rated 10 degrees and higher have proven to be reliable, studies have shown that it is not a statistically reliable way to rate the temperature rating of sleeping bags rated below 10 degrees, including all winter sleeping bags.
Instead, sleeping manufacturers rate their own sleeping bags by having people sleep in cold rooms, basically walk-in freezers, to see if they stay warm at different temperature settings. This can generate very subjective results depending on who does the testing, whether they’re male or female, what their body weight is, how well a sleeping bag fits them, the warmth of the long underwear they’re wearing, whether they’re wearing a hat or not, what sleeping pad they’re using when they last ate, and so on.
So who can you trust? Your best bet is to buy a winter sleeping bag model that’s been on the market for a while and has a loyal following of people who will attest to the accuracy of its temperature rating.
Feathered Friends and Western Mountaineering have built their business around word-of-mouth testimonials, which is why people prefer their winter sleeping bags over all others. No one else provides the range of selection or technical features provided by these two manufacturers.
There are all kinds of tricks to extend the range of a 0-degree sleeping bag for colder weather, especially if gear weight or bulk is a big concern:
It is best to experiment with these in your backyard or within walking distance of your car before you need to count on them in a wilderness survival situation.
If you are on a major expedition and your guide requires a -20 degree or -40 degree bag for sustained frigid weather, you should consult with them about using a winter sleeping bag rated for warmer temperatures. Many guides rent cold-weather bags, which can save you the expense of buying one for one-time use.
Another option is to cancel trips where you know the weather will be too cold for your sleeping bag. As a winter backpacking trip guide, my partners and I routinely cancel trips where the weather forecast calls for -20 nighttime temperatures since it’s really no fun to sit outside and melt drinking water in weather like that. There’s no shame in bailing on a trip when it’s too cold outside to enjoy yourself.
Women tend to sleep colder than men, so it’s recommended that they get a sleeping bag that is 10 degrees warmer when buying a unisex or men’s sleeping bag. For example, women should buy a -10 degree winter sleeping bag in order to stay as warm as a man in a 0-degree winter sleeping bag. However, that’s not the case, if you buy a winter sleeping bag designed for a woman. A women’s 0-degree winter sleeping bag should keep you as warm as a men’s 0-degree sleeping bag.
Women’s sleeping bags are often shorter in length, narrower in the shoulders, and wider in the hips. They may also have extra insulation over the chest, in the hood, and in the foot box, since women have a harder time keeping their heads, hands, and feet warm.
Sleeping in a winter sleeping bag is different from sleeping in a three-season or summer sleeping bag because you need to sleep with some of your gear from freezing overnight (boots, water bottles, electronics) or because you need to wear additional insulated clothes in your sleeping bag like a down parka and down-filled pants.
To size up, people typically get a longer-sized sleeping bag or one that has a wider shoulder girth. Shoulder girth measures the circumference of the sleeping bag at shoulder height. When fitting a winter sleeping bag, you want to minimize the amount of extra interior free-space that your body has to heat up while not compressing the loft of your insulation by getting a bag that’s too tight.
For example, a 5′ 10″ tall man might opt to get a 6′ 6″ long bag instead of a 6′ long sleeping bag in order to store some of his gear in the sleeping bag foot box. Alternatively, you can opt to get a bag with wider shoulders or chest measurements so you can hug your extra gear at night to keep it warm or tuck it behind your back (if you’re a side sleeper.) That’s always been my preference, instead of getting a longer-length sleeping bag.
How do you determine your needs and preferences? Try on lots of sleeping bags while wearing your overnight gear, even if it means buying bags and returning them to retailers if they don’t fit.
After fit, the most important features are having a draft collar, draft tubes, zipper guards, and a well-fitting hood. It’s also important to get a sleeping bag with a breathable external shell that can vent perspiration but is water-resistant. Sleeping bags with waterproof/breathable shells are often less breathable than those without a waterproof/breathable external fabric.
A draft color is an insulated tube insulation that covers the top of your chest and back and seals in all of the warmth below it in your bag so it can’t escape. It prevents what’s called the “bellows effect”, where the warm air around your legs and core is forced out through the top of your sleeping bag when you move around at night. You can achieve a similar effect by wrapping a weather or down jacket around your upper chest or neck as well.
A draft tube is an insulated tube of insulation that runs along the zipper and prevents cold air from leaking into your sleeping bag or warm air from leaking out. Some sleeping bags like the Western Mountaineering Puma -25 have two interlocking draft tubes, one above and one below the zipper.
A zipper guard is a piece of fabric or stiffened fabric tape that runs along a zipper and prevents it from snagging on the inside lining of your sleeping bag. It’s an important feature of a sleeping bag since it eliminates snags that can prevent you from closing the zipper in frigid weather.
A baffle is a fabric tube containing down or synthetic insulation. They’re usually oriented horizontally or vertically in sleeping bags.
Continuous baffles are fabric tubes filled with down insulation that usually run horizontally around a sleeping bag. They let you shake the down inside them to move it where you want it, usually to the top of a sleeping bag, or down the sides. Found in high-end quilts and sleeping bags like those from Feathered Friends or Western Mountaineering, continuous baffles are a highly desirable feature for some people that lets you move the insulation to the parts of you that are cold. For others, it’s a curse, because the down insulation can shift where you don’t want it to go, creating cold spots.
Blocking baffles, also called side block baffles or V-block baffles are used in high loft, winter expedition sleeping bags to prevent down from shifting from the top of a sleeping bag to its sides.
Unfortunately, they’re mostly cons. The idea of covering a sleeping bag with a waterproof/breathable shell fabric is appealing because it would mean that you don’t need to carry a bivy sack to sleep in a snow shelter or worry about getting internal condensation on the outside of your sleeping bag when you touch your tent’s walls at night. But experience has shown that covering the exterior of a sleeping bag with a waterproof breathable shell tends to trap more perspiration inside the insulation of a sleeping bag than one with a much lighter shell fabric.
Contrary to what you’d expect, waterproof/breathable fabrics are actually far less breathable than most of the non-waterproof shell fabrics used on the exterior of sleeping bags today. You can get the same waterproof benefit by spraying a DWR coating on the outside of this lighter-weight, more breathable fabric, which will repel water droplets that fall onto the outside of the bag, causing them to bead and roll off, just like a rain jacket. Most sleeping manufacturers already do this at the factory. But if the DWR coating wears off, you can apply it at home using Nikwax TX Direct or similar products.
In addition, most sleeping bag manufacturers don’t tape or seam seal all of the seams in their bags, which is really required for true waterproofing. Think about all of the tiny needle holes in the baffling of a down bag. Taping or seam sealing them all would be very costly. In contrast, most bivy bags made with waterproof/breathable fabrics have taped seams or can be easily sealed with a seam sealer. You really can’t do the same with a sleeping bag.
You want an external shell fabric that is tough enough to be durable and has good breathability, with a tight enough weave and/or a DWR coating that will make water roll off its surface. Pertex Shield and microfiber calendared nylon are good examples of fabrics with these properties.
This is an area of personal preference, but you want a hood that will fit around your head without any air gaps that leak warmth. It should be easy to adjust (many aren’t), move with you if you roll onto your side, and not become saturated with water vapor when you exhale at night through your mouth. The best way to determine hood fit is to get inside a sleeping bag and try it out. It’s important to get a hood that you can spend 12 hours or more in comfortably since winter nights are so long.
A winter sleeping bag without a high R-value sleeping pad is like a sheep without wool. Without one, your body heat will be sucked into the cold ground. We recommend using a sleeping bag with an R-value of 5 or better. R-values are additive, so you can also use two sleeping pads, one stacked on top of the other to achieve a higher composite R-value. Many winter backpackers will carry a foam pad, which can be used as a seat when cooking or snow melting, in addition to an inflatable sleeping pad for comfort. When choosing winter pads, we recommend using ones that have been rated using the new sleeping bag standard, such as the Therm-a-Rest XTherm, which has an R-value of 6.9.
