Choosing a sleeping bag is probably one of the more complicated gear purchase decisions, for outdoor neophytes and seasoned backcountry veterans alike. There's a lot to consider—weight, packability, warmth, comfort—and there's a lot of sleeping bags to choose from.

Read on to sort through what you'll need to know to get the right sleeping bag for you.

Choosing a sleeping bag by Activity

The first thing you'll need to decide is what activity you need a sleeping bag for. Are you camping in the front-country, or backpacking for an extended period of time? Are you mountaineering, or packrafting? The weight, shape, and features of sleeping bags are often best-suited to specific end-uses, so it's important to choose one based on what you anticipate using it for the most.

Camping Sleeping Bags

A sleeping bag for camping is one that you wouldn't want to haul around in your pack for any appreciable distance. They're heavier, bulkier, and more geared towards comfort than sleeping bags made for backpacking. That being said, it's this focus on comfort that makes them fantastic for family car camping trips and other front country sojourns, and since they are less technical, they are also much less expensive.

Any sleeping bag can be a camping sleeping bag, but since front country excursions don't require anything overly technical, take the opportunity to save money and be comfortable. From left to right: The Eureka Lone Pine 0°, the Women's Kelty Galactic 30°, and the Women's Marmot Trestles 30°.

Look For: Anything you like! As long as the temperature rating is correct for the time of year you're camping, you can spend as much or as little as you like, get whatever shape is most comfortable (rectangular sleeping bags give the most space to move around), and get whatever fill you like (down lasts longer than synthetic fills, but is more expensive).

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Backpacking sleeping bags

With backpacking sleeping bags, weight and compressibility should be your main considerations. Cramming a bulky sleeping bag into a stuff sack and having it take up a ton of space in your pack is never ideal, and as part of the "Big 3" that determines your backpacking base weight (shelter, sleeping bag/pad, and pack), the lighter your bag is, the better.

The trick to picking out the right backpacking sleeping bag is balancing weight and compressibility with the correct level of warmth, so keeping an eye on temperature ratings is important.

A sleeping bag for backpacking should be as lightweight and compressible as the temperature (and your wallet) will allow. From left to right: The Marmot Nanowave 50°, a synthetic bag weighing in at 1 lb 15 oz; the Sea to Summit Spark SP I, an 850-fill down bag that weighs a spartan 12.4 oz; and the NEMO Ramsey 30°, a fully featured down bag weighing in at 2 lbs 1 oz.

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Look For: Try to get the lightest sleeping bag you can afford while keeping it warm enough to sleep comfortably. Low denier shell fabrics and high fill power down will get you the greatest weight savings and best compressibility, but at a premium price. Try to shoot for a sleeping bag weight of 2 lbs or less.

Alpine climbing / Mountaineering sleeping bags

Choosing a sleeping bag for alpine climbing and mountaineering is a lot like choosing a sleeping bag for backpacking, but with an added focus on warmth and water resistance.

In order to remain as light as possible and still have enough insulation to keep you warm in alpine environments, these kinds of sleeping bags will use some of the highest quality insulation available, and that can make them expensive. Their shell materials will also often feature waterproof/breathable membranes and water repellent coatings to deal with increased moisture levels.

Well-fitting hoods, draft-resistant zippers, resistance to condensation, and copious amounts of down make for a sleeping bag that can stand up to tough alpine environments. From left to right: The Rab Neutrino 400 25° bag; the North Face Inferno 15° bag; and the Sea to Summit Alpine III 10° bag. All three of these sleeping bags tout their water resistance and the quality of their down insulation, and their prices reflect that.

Look For: Warmth, water resistance, and features that improve those aspects in particular. Pack weight and space are at a premium in the mountains, so getting the lightest, most compressible bag possible should be your aim.

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Sleeping Bag Temperature Ratings

Sleeping bag temperature ratings represent the lowest temperature at which a sleeping bag can be used. For example, a 35° bag will keep you warm down to around 35°, and below that temperature you will start to feel uncomfortably cold.

First and foremost, temperature ratings are created with the assumption that you are using a sleeping pad, so don't forget one! When you lay in a sleeping bag, you are compressing the fill material underneath you, which renders its insulating capabilities moot. A sleeping pad puts another couple of inches of insulation between you and the cold ground, and increases the effectiveness of the bag you are in.

Temperature Ratings and Seasonality

If you aren't planning on high altitude expeditions, you can use the list below to correlate temperature ratings to seasons. Since temperatures in the mountains are quite a bit colder than temperatures at lower elevations, seasonality goes out the window—shop by anticipated temperatures instead.

Summer Bags: 35 degrees and up
3-Season Bags: 15 - 30 degrees
Winter Bags: 10 degrees and under

While you'll have a hard time finding anywhere (relatively close to sea level, anyway) that's 35° during the summer, bags with this temperature rating and above are the best choice for warm weather. Likewise, spring and fall temperatures don't usually get down to 20°, but a 20° bag is highly versatile and can deal with shoulder-season conditions well. If you're camping in the dead of winter? You'll want at least a 10° bag, and more likely, a 0° or lower bag.

Think about how hot or cold it will actually be on the trips you intend to take, and buy accordingly.

Pro-Tip: A 20° bag will get you through most of the year without too much discomfort. For very warm temperatures, it's easy enough to unzip the bag and kick a leg out, and for cold temperatures, wearing extra clothes and using a sleeping bag liner can buy you an extra 10-15 degrees of warmth.

Sleeping bag Fill type — Down versus Synthetic

On the left: A pile of down feathers. Right: A sheet of synthetic insulation.

Down insulation in sleeping bags is, on the whole, the superior choice. Down's warmth-to-weight ratio is better than any synthetic fill, it's highly compressible, and it keeps lofting even after stuffing your sleeping bag into a compression sack hundreds of times. If you want the lightest, most durable sleeping bag possible, you'll want a down one.

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The great equalizer for synthetic insulation is its ability to keep you warm even after it's been soaked through with water—something that remains out of reach for down (though great strides have been made with water-resistant treatments for down). Synthetic insulation also dries out much faster than down can, and is much less expensive. This traditionally has made synthetic sleeping bags the best choice for trips that have a very high chance of becoming very moist—trekking in Patagonia, for instance, or alpine climbing in the PNW.

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But...

REAL TALK: While the financial advantage of buying a synthetic-fill bag can't be understated, and the fact that they don't use animal products in their construction is an important and valid factor to many, the 'synthetic fill insulates better when wet' argument just isn't a very good one for ignoring all of the benefits of a down bag.

The fact is, it's not hard to keep a down bag dry even in very wet conditions—just store it in a roll-top drysack and use a pack liner, and don't take it out until you're sheltered from precipitation.

Down Fill Power

Down fill power is a numerical rating system that represents how "lofty" the down in your sleeping bag is—the higher the fill power, the more air gets trapped by the down. A higher fill power down will keep you warmer with less filling, making for a lighter sleeping bag.

Comparison of different fill powers. Each cylinder contains the same amount of down by weight.

How is Down Fill Power Measured?

To measure fill power, manufacturers take a one ounce sample of down and put it into an enclosed graduated cylinder. Then, a one ounce weight is then placed on the down to compress it. The weight is then removed and the down is left to loft for a period of 72 hours. The height that the ounce of down lofts to (in cubic inches) is the fill power.

Is an 800-fill 30° bag warmer than a 600-fill 30° bag? No, they will provide the same level of warmth. It will just take more 600-fill down to do so, which means it will be heavier.

Common Down Fill Power Values

550 - 600 fill: On the low end of the spectrum, this fill power makes for the most affordable down bags. Though it can be relatively heavy and less compressible, it's still lighter and more compressible than synthetic fills.
700 fill: Used in mid-range down sleeping bags, this fill power strikes a decent balance between cost and weight savings.
800+ fill: 800, 850, 900, 1000 fill power—these are the most expensive sleeping bags you can get, but their ultra light weight and their ability to compress to very small sizes make them particularly prized by those who want the lowest pack weights possible. Winter bags with this grade of premium down can run upwards of $1000, just by virtue of the fact that they're stuffed with so much of it.

Sleeping Bag Construction

This is where 'Sleeping Bag Basics' ends, and 'Advanced Sleeping Bags' begins. The different shapes, fabrics and features of sleeping bags are what make choosing one so complicated, so read through this section carefully, and you should get enough information to make a relatively educated decision.

Different Sleeping Bag Shapes

Rectangular Bags

A rectangular sleeping bag is the most common shape for recreational camping. They are the most comfortable shape of traditional sleeping bag, as they allow you to spread out and sleep in a natural position. Their drawbacks are that they are heavier and bulkier due to extra material. They are also less efficient at keeping you warm, since there is more dead space in them for your body to heat up.

Rectangular sleeping bags can be totally unzipped and used as a blanket—or zipped together with another rectangular bag to create a double bag.

Double Bags

Great for couples' camping, getting a double bag and sharing a partner's body heat is by far the most efficient way to keep warm. Ones made for recreational camping are some of the largest and heaviest bags you can find, however, so only get one of those if that's all you plan to do with it.

Double bags made for more technical pursuits, like alpine climbing or ultralight backpacking, are a great option to cut you and your partner's total pack weights, since you can rely more on each other's body heat for warmth and get a lighter bag than you would otherwise need. Just make sure that if your partner is carrying it, you carry an extra part of the tent, or more food or something. Be equitable.

Mummy Bags

Mummy bags are the lightest traditional sleeping bags (for the lightest non-traditional sleeping bags, read about quilts below), with the caveat of being rather uncomfortable for some people, and downright claustrophobic for others. Their tightly sculpted shapes not only make them much lighter than a rectangular bag, but also make them very efficient at keeping you warm since there is very little dead space for your body to heat up.

Beware of a mummy bag that is too tight, though—there needs to be at least some air circulating around your body for a sleeping bag to work properly. Keep this in mind especially if you plan on wearing extra layers in your bag to pad out its temperature rating.

Specialized Shapes

On the left: a semi-rectangular bag from Sea to Summit. Right: A NEMO Spoon bag.

Semi-rectangular bags attempt to bridge the gap between mummy bags and rectangular bags, and are a good option for people who want to save some weight but don't want to feel entombed.

Nemo's Spoon bags are another shape option aimed at increasing comfort without adding too much weight, featuring an hourglass-esque shape that's made with side-sleepers' knees in mind.

Quilts

Different configurations of the Sea to Summit Ember EB I quilt.

Quilts are a (relatively) new development in backcountry sleep systems. They operate under the assumption that since all of the filling in the bottom of a sleeping bag is being compressed underneath you when you lay on it, it might as well not even be there at all—and it isn't. Instead, you lay directly on your sleeping pad and draw the quilt around your body, with your legs and feet in the lower third of the quilt that is either totally enclosed or zipped together.

Quilts feature removable, adjustable strap systems that integrate with your sleeping pad to make sure they stay put and don't let in drafts in cooler temperatures. Since quilts use less material, less filling, and have either no zipper or a significantly smaller one, they are some of the lightest sleeping bags you can get today.

Women's-specific sleeping bags

Comparison between the men's (left) and women's (right) version of Marmot's Phase 20° sleeping bag.

Women's-specific bags are constructed slightly differently than unisex sleeping bags, namely in that they are cut to be narrower in the shoulders, wider in the hips, and they come in a range of shorter lengths. They also come with added insulation.

Shell and Lining Fabrics

Most sleeping bags are made with DWR-treated nylon ripstop shell and liner fabrics, which are lightweight, very comfortable, and allow for sleeping bags' fillings to loft especially well. The more expensive your sleeping bag is, the lighter and thinner this nylon fabric will be—and the specification you will want to look for to quantify this is denier. The weight difference per square yard between a 10D and a 40D nylon fabric (the 'D' standing for denier) is significant, and ultralight sleeping bags are often so thin that you can see right through them to the down feathers inside.

Sleeping bags for recreational camping will sometimes use more "old-school" fabrics than nylon (like cotton and flannel), and this can be particularly nice in cooler temperatures. For camping in warm or humid weather, nylon will remain cooler and dry faster, though.

Waterproof/Breathable Membranes

These are mostly used only in sleeping bags that are specifically for alpine climbing and mountaineering; a waterproof/breathable membrane will help them remain dry in the face of the heavy, iced-over condensation that can occur in a buttoned-up mountaineering tent.

For most people, they're not really needed, as the DWR coating on the shell fabric is enough to deal with light condensation.

Zippers

Snag-Free Zippers

There's nothing worse than getting your sleeping bag's zipper snagged in that oh-so-delicate fabric, so do your best to find a sleeping bag that was made with one that attempts to be snag-free. The smaller and daintier the zipper, the more likely it is to snag, so look for larger, sturdier teeth, as they will zip and unzip more smoothly. Also, look for a stiff backing along the length of the zipper, as that will prevent the fabric from bunching.

Left or Right Zip?

Choosing a left or right zip is pretty simple: If you're right-handed, get a sleeping bag with the zipper on the left. If you're left-handed, get one with the zipper on the right.

Think of it this way: If you're lying on your back, it will be much easier for your dominant hand to reach over your body to use the zipper, rather than the chicken-arm maneuver you'd have to do if the zipper was on the same side as your dominant hand.

Draft Tubes

If you're getting a sleeping bag that you'll use in cooler weather, look for one with a draft tube; it's a chamber filled with insulation running along the length of the zipper. The zipper is basically a sleeping-bag-length weak point for cold drafts without one. If you're getting a summer bag specifically, then don't worry too much about it.

Baffles

A sleeping bag's baffles are the chambers that contain the bag's insulation. With down bags, you'll see a lot of different configurations of these, but the two most common types are vertical and horizontal baffles. Synthetic bags' baffles are mostly just for show, so don't worry about them too much.

Vertical Baffles

Vertical baffles are great for sleeping bags that have more dialed-in shapes, and their sculpted hoods and footboxes are generally more comfortable than those from horizontally-baffled sleeping bags, particularly for people who sleep on their backs.

The drawback to sleeping bags with vertical baffles is that they need mesh walls sewn along their length to prevent their down filling from migrating, so they are heavier than a horizontally-baffled sleeping bag of the same temperature rating and quality.

Horizontal Baffles

Sleeping bags with horizontal baffles are warmer by weight than vertically-baffled sleeping bags, though they can't be sculpted into ergonomic wonders like them. That's less of a problem if you sleep on your side, though.

If you want a truly versatile sleeping bag, look for one with continuous horizontal baffles. Continuous horizontal baffles wrap around the entire circumference of the sleeping bag, and that means that you can move your down insulation around as you see fit to dial in your warmth level. Too cold? Shake all the down out from the bottom of the bag so there's twice as much on top. Too warm? Shake it out from the top so all the down is beneath you.

Hoods

The colder the temperature is, the more important a hood for a sleeping bag becomes. A bag strictly for summer use won't necessarily need a hood, and there are plenty of sleeping bags that are made without them to save weight.

The most important thing to consider as far as hoods are concerned is how well one fits around your head. An ill-fitting hood will not only be uncomfortable when drawn tight, but as you move around throughout the night you can get "lost" in the hood and start breathing wator vapor into your sleeping bag, making it damp and even more uncomfortable. If you're able, heading to a gear shop to try out sleeping bags in-person is the most surefire way to know if the hood is right fit for you.

Sizing your sleeping bag

The length of sleeping bag you need is based on your height, and it's important to not get one that's too short or too long. If your sleeping bag is too short, your feet and head will press against the ends of your bag, compressing the insulation there making it less effective. If your sleeping bag is too long, there will be too much dead space in it and it will take more energy (and longer) to heat it up.

That being said, it is acceptable to get a longer sleeping bag if you plan on keeping gear that needs to stay warm in the footbox, like boot liners or electronics.

Sleeping bag lengths are standardized across different brands, with men's and women's bags being either regular or long.

Men's Regular: 78 inches long (fits someone up to 6')
Men's Long: 84 inches (fits someone up to 6'6")
Women's Regular: 72 inches (fits someone up to 5'6")
Women's Long: 78 inches long (fits someone up to 6')

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