How to Pick a Sleeping Bag
Picking a sleeping bag can be slightly overwhelming, as there are a number of variables to take into consideration. And if I remember anything from math class, it's that variables are confusing. They vary, for crying out loud. Why can't they stay constant like whatever those constant numbers are called? Anyways, we'll go through this sleeping bag stuff together and it'll all become really clear. You just need to have an idea of what kind of trips you'll be taking. There isn't one perfect bag that will work for all your trips, but with careful selection, you can get the most range out of the ones you do buy.
Sometimes a sleeping bag is just a sleeping bag. Sometimes it isn't.
MATCH YOUR BAG TO THE ACTIVITY.
Certain sleeping bags are more practical for specific activities. Think about what activity you are going to do before taking the plunge on your sleeping bag purchase. Some sleeping bags can and will overlap for different activities, but some just won't. For example, you wouldn't use a mountaineering sleeping bag on a summer ultralight thru-hike of Michigan.
BACKPACKING - If you're a backpacker at heart then the sleeping bag you're looking for should compress down to a reasonable size, allowing you to fit it into your backpack and carry your bed on your shoulders and hips. Pay attention to the warmth-to-weight ratio so you don't freeze during the night and so you won't break down from carrying too much weight on day 2.
MOUNTAINEERING - The mountaineer will need to be looking into the incredibly warm sleeping bags due to the environment, but keep an eye out for different shell fabrics to combat moisture. I wouldn't worry about the weight of the bag, because the more insulation you have, the warmer you'll be. In extreme cold, if you're toasty warm then you'll just have to bite the bullet when it comes to extra weight.
ALPINE CLIMBING - Alpine climbers typically move fast and to do so you'll need something light and warm. The shape of these bags are often quite tight to reduce weight while allowing for more insulation to combat colder temperatures of the mountains.
CAR CAMPING - Go. Nuts. Seriously, when car camping you don't have to worry about jamming your bag into a tiny backpack, so get the biggest, fluffiest thing your wallet allows. Get a giant two-person bag and share the bed with your lover. Forget the encapsulating mummy shape and get a big old blanket. There really isn't anything to stop you from dreaming up a cozy bed.
Seasons + Temperature
'Tis the season for some nature.
BUY A BAG FOR THE COLDEST TEMP YOU'LL ENCOUNTER.
If you're headed into the outdoors, make sure you take into account what season it currently is and what season you'll be ending your trip in. Just because you head out on a bright spring morning doesn't mean you'll be returning before the sweltering heat of summer. You'll need to find a sleeping bag that can keep you warm at the lowest temperature you'll be meeting. Don't stop there, you'll also need to consider your environment, because spring in the high mountains is a whole lot different than spring in the marshy lands of the Deep South. Lastly, when temperature ratings are calculated, it is standard practice to factor at least a 1" sleeping pad, with the sleeper wearing a top and bottom base layer AND a hat.
-40 to 0 DEGREE FAHRENHEIT bags are often described as winter. While yes, you'll probably need a bag within this degree range to sleep in when exploring the outdoors in the winter, don't let that be the stopping point for your purchase thought process. Are you mountaineering? When it comes to the mountains you can often be surprised how you can hit incredibly cold weather, even in a so-called spring or summer month.
5 to 25 DEGREE FAHRENHEIT bags are often called "two or three season", as they're able to cover most temperatures met in the outdoors in spring, summer and fall. Just be sure you're checking the temperatures for the area you'll be exploring, not just noting the season. Summers can be cold too. If you only have the cash to buy one bag and plan to do a lot of outdoor exploring, something in this range will offer the most bang for your buck. Plus there are always ways to bolster the warmth when going on a one-off winter camping adventure.
30 to 55 DEGREE FAHRENHEIT are typically reserved for summertime sleeping. While it is certainly possible to see these temperature ranges in spring and fall, you probably won't want to chance it. The more time you spend in the backcountry, the more likely you are to meet a rapid and unexpected change in temperature. If you're a fair weather, warm temperatures only kind of hiker, this range will be a great option for you.
EN Temperature Rating
Check the temperature rating of a bag before ordering.
In the good old US of A, sleeping bag temperature ratings are not standardized. What this means is, companies can put a rating on a bag, and it might not come up to scratch when comparing it to bags from other companies. Europe has developed rating system and a solid amount of companies are using it. Well, never fear Americans (and all others), this actually helps you out as you shop for a new sleeping bag. The EN Temperature Rating, or EN 13537, is the result of standardized tests that check certain comfort benchmarks and survivability benchmarks. It has been adopted by most of the industry to get all the companies on the same page. It's probably run by a secret panel of mad scientists and regular scientists, so trust it when you see it. No more guessing if that 30 degree F bag is the same as that other 30 degree F bag. Unless of course it doesn't have an EN rating listed.
The stuff that keeps you warm.
Down will be warmer, and synthetic performs better in wet conditions.
If you meet a gear junkie, you can typically get them into a long, drawn out conversation about insulation. Which is better, down or synthetic? The world may never know the true answer to this question, as there are great arguments for each. The best part is, as technology gets better, the two types can be engineered or altered to perform even better than their predecessors. Science is great.
DOWN - Down insulation is the warmest insulation by weight. It is extremely compressible and retains loft very well. The natural fibers efficiently trap your warm air and hold it right next to your body. Down bags are excellent for any backcountry activities and are perfect for lightweight backpacking. When it comes to down, you'll hear the words "fill power" quite a bit. Fill power is the measurement of loft in an ounce of down. The higher the fill power number, the higher quality the down is and the less amount of down it takes to fill up your bag. Fill power numbers range between 500 and 900. A quick example: Take two 30°F sleeping bags, one with 600 fill power down and one with 800 fill power down. The 600 fill power bag will be heavier, won't compress quite as small to fit in your pack, but will be less expensive. The 800 fill power bag will be lightweight, compress into your pack smaller, but will come with a big price tag. The kicker? Both bags will still keep you warm on a 30°F night.
SYNTHETIC - Synthetic insulation is a little heavier than down, but excels in wet conditions. Due to its polyester fiber structure, it can still trap warmth impressively well when wet. I heard dog fur makes a great insulator, but smells terrible when it gets wet. When it comes down to it, a soaking wet bag is going to be the worst, regardless of the type of insulation. When thrown side-by-side, a wet synthetic bag will outperform a wet down bag. Plus, it will at least dry out a bit faster. Really the best solution is to make darn sure that your bag doesn't get soaked. Plus synthetic insulation usually costs a little less.
HYBRID - Down and synthetic insulation are expertly mapped to targeted areas to balance warmth, compressibility and versatility. Magellan would be proud (that's a joke about mapping).
Beauty comes in all shapes and sizes.
Pick a bag shape that fits your sleep style.
MUMMY - The most common shape when it comes to backpacking and mountaineering sleeping bags is the mummy. Seriously, just like a mummy of ancient times it wraps your body closely, but in this case, not to preserve. Here it traps warm air, and since there isn't a ton of space, you warm up more quickly. No chance for the midnight chills. Great for staying toasty through the night, but if you're claustrophobic you may want to look into other shape options.
SEMI-RECTANGULAR - The semi-rectangular shape is just as you would imagine it, right in between the mummy and rectangular shapes. It works well for those with bigger shoulders or bodies, but still cuts down on weight when it comes to throwing into your backpack.
RECTANGULAR - Rectangular, it's a simple shape you learned about way back in kindergarten, or maybe even before. This shape is typically reserved for sleeping bags meant for car camping, but can sometimes be found in lightweight summer bags that can be taken on shorter summer trips. You can usually unzip these ones to lay out flat, for use as a blanket.
SPOON - Rarely seen, but definitely available is the spoon shape. To some, it may look more like an hourglass shape. Either way, it is produced for those that sleep on their sides. Side sleepers need more space when curling their knees up towards the chest, and this shape allows them to do so, without having to twist awkwardly through the night.
BED-STYLE - Bed-style sleeping bags are on the newer end of the spectrum, so pay attention early-adopters! At first glance, they look much like a sleeping bag, with a mummy, semi-rectangular or rectangular shape, but they won't have any zippers. There is a large section cut out at the top, center of the bag, which is where you enter, feet-first, from. Then, a little blanket can be pulled over top, folded down, tucked inside. One part sleeping bag, one part blanket. The comforts you want while in the wilderness with the added snuggly security of wrapping a blanket around your shoulder and neck area.
BLANKET - Blankets aren't so much sleeping bags, sorry for the confusion. Some rectangular bags can be unzipped to function as a blanket as mentioned above, but some technical blankets are only made to lay flat. Sometimes they can be snapped or strapped to your sleeping pad, or they can even just be laid out underneath your body for a bit of softness. These are more often reserved for use as extra warmth, summertime trips, or just a bit of cuddling.
Does it really matter?
A women's specific bag will be slimmer and lighter weight.
Sleeping bags are gender specific, believe it or not. This does not mean that if you're a man you have to choose a men's bag and if you're a woman you have to choose a women's bag, but there are good reasons they are made this way. Women tend to sleep a little colder than men. There is some science about body mass behind it, but men tend to sleep 5-10 degrees warmer than women. The women's bags will usually have the appropriate amount of insulation to combat this and also sometimes place additional insulation in specific sections, like the footbox as ladies tend to have colder feet. Men's bags are usually longer and wider, so getting a women's bag will mean shorter length and less width. If you're a short, skinny dude, go ahead, get a ladies' bag. I won't tell. Lastly, let's not forget kid's bags. They're much, much shorter than adult bags and weigh less, so your budding outdoors-kid won't have to fill out empty space in their sleeping bag and it also won't weigh them down when hiking.
Very different than what's on a turtle's back.
A sleeping bag shell fabric can be crucial in harsh conditions.
Without a shell fabric you'd just have a bunch of insulation lying about which wouldn't be very warm or cozy. The shell protects the insulation, keeps it in place (usually with the help of baffles) and is usually coated in a durable water repellant finish to prevent light moisture from soaking in.
NYLON is the most common shell fabric you'll find. It is incredibly lightweight and packs down easy while still protecting the insulation that has been packed inside. For ultralight sleeping bags, 10 or 15 denier is common.
MICROFIBER is a more durable shell fabric, offering not just more protection from abrasion, but also weather resistance. It still breathes so you don't overheat in the bag, but it helps keep wind out due to the tight weave.
GORE WINDSTOPPER® isn't very common, unless you're looking for an expedition sleeping bag. It's really tough, windproof, and also offers the best resistance to moisture (although it is NOT waterproof).
Which side are you on?
This is not a no-brainer. Consider how you sleep, and which side of your tent the door is on.
Right or left zip isn't a critical decision and isn't always an option. Right or left zip refers to which side of the sleeping bag the zipper is on when you're lying on your back. So don't assume that since you're right handed, you should get a right zip. It's usually more comfortable and intuitive for right handed people to buy a left zip bag (and vice versa). The other consideration is which side of your tent the door is on. It can be convenient (but not necessary) to have your bag open up to that side for getting in and out of your tent or for accessing your vestibule. If you're ambidextrous, congratulations, the world is your oyster and you can pick whichever side you like.
Sometimes it's about the little things.
A few small features can make a big difference in your sleeping bag of choice.
DRAFT TUBE + COLLAR - The majority of technical sleeping bags (those meant for backpacking, mountaineering, or climbing bags) will include a draft tube and collar. The draft tube runs along zipper on the inside of the bag. It is filled with insulation and blocks drafts from sneaking their way through the opening. The draft collar is a similar shaped tube, but softly wraps your neck area, where the hood meets the bag. As in the name, this too blocks drafts. Absolutely necessary in the most frigid of temperatures, but when it comes to summer bags, some just don't have 'em.
HOOD - Sleeping bags have hoods, so your little head can snuggle inside and get in on the warmth. Most bags will have a hood, but most often you won't find them on rectangular bags.
ZIPPERED STASH POCKET - Stash pockets are pretty small, located right near the top of your bag. If your bag has one they can be pretty darn handy. They are meant to zip something small that you might need to grab quickly in the middle of the night. Head lamp. Lip balm. Watch.
Which side are you on?
Great for adding warmth, keeping your bag interior clean, or sleeping comfortably in high temps.
Sleeping bag liners come in several different fabrics and weights such as fleece, synthetic, cotton and even silk. There are three main purposes for using them, but you don't have to unless you want to.
WARMTH is a great reason to add a liner, especially during winter camping. The thicker fleece liners are a great option here. There are even some liners that use a reflective material, allowing your own heat to bounce back at you.
CLEANLINESS is a solid reason for adding a liner to your bag, because face it, after just a few days on the trail you can get pretty stinky and dirty. Save your expensive sleeping bag from the extra grime and add a lightweight cotton or synthetic liner. The lighter ones won't add much weight or warmth but they'll feel nice and you'll be able to go longer between sleeping bag washings, which can take lots of time and effort to do properly.
DITCHING THE BAG is my favorite reason for liners. If you're going out for a super short overnight and the weather is incredibly hot and sticky, just grab your liner and go. Not a good option for long trips, but you can get away with it on certain occasions. The silk liners are so soft and comfy against the skin, you'll even want to bring one along when you travel. Much nicer than sleeping on questionable sheets at the motel or hostel.
Stuff, Compression + Storage Sacks
Know the difference!
A compression sack can cut the size of a packed sleeping bag in half.
You'll need to have something to jam that big, fluffy sleeping bag into before heading out into the wilderness. Proper care should also be taken to your bag once you arrive home.
STUFF SACKS are great for holding onto the little things, like clothing, kitchen gear, a first aid kit. Not so much for sleeping bags.
COMPRESSION SACKS will compress a sleeping bag down mighty small, as small as the size of your sleeping bag will allow it. This way, you can jam it into your backpack of choice and still have space for the rest of your gear. It is typically recommended you get a waterproof one, because nature tends to do its own thing like rain, snow, sleet. Even rivers can get a hold of your backpack. A soaking wet sleeping bag won't keep you warm at night, so do yourself a favor. It's worth noting many backpacking sleeping bags these days come with an ultralight compression sack made of nylon, which isn't waterproof. You make the best decision for you
STORAGE SACKS are what you can put your bag into when at home, lamenting the fact that you're not out in nature. The best way to store your sleeping bag is lying flat, perhaps underneath a bed where the cat won't take a nap on it. Not everyone is lucky enough to have enough space to lay a bag flat however, so storage sacks are the next best option. It allows the bag to fluff out and the insulation to breathe. If you store your bag in a compressed state, the insulation will get all sad and floppy and when you go to use it next season, it won't loft up as nice, leaving you cold through the night.
Now get out there already
Sleeping bags are like a little cocoon you snuggle up in at night, only to be reborn each morning as a well-rested, happy hiker. It's a beautiful metamorphosis, unlike the butterfly metamorphosis which is mostly gross (did you know they turn into a goo in there?). By tailoring your sleeping bag options to your own personal preferences, you can make your rebirth all the more enjoyable.