Have you ever been excited about going camping, only to experience a cold, nearly sleepless night that left a bitter taste in your mouth on the drive home? Chances are, your sleeping bag was mostly to blame.
A sleeping bag is your most important piece of equipment for staying warm and comfortable during nights spent outside. People use sleeping bags in lots of different situations, though. There's car camping, open-air summer camping, backcountry camping, winter hut trips, indoor sleepovers. well, you get the point.
To meet the wide range of consumer demands, manufacturers have designed many types of sleeping bags from which to choose. It may sound obvious, but you wouldn't wear the same jacket on a cool spring evening as you would wear during a winter blizzard; likewise, you wouldn't expect any old sleeping bag to keep you comfortable in all situations. One bag does not fit all, so this guide is intended to help you narrow down sleeping bag selections to the bag that's just right for you.
Sleeping bags are designed for specific temperature ranges to meet the demands of different climates or seasons. A bag's temperature rating or comfort rating can be defined as the absolutely coldest temperature at which the bag is designed to keep you warm. There is no industry standard for determining a bag's comfort rating, though, and no two people are exactly alike (for example, women are generally colder than men in the same air temperatures). Therefore these temperature ratings are meant only as general guidelines.
We've found these ratings to be most accurate under a set of specific conditions: if you are fully sheltered from the wind (inside a tent or other structure) and have some sort of sleeping pad underneath you, these minimum temperature ratings apply best.
To be on the safe side, we recommend adding 10 degrees to the temperature rating on a sleeping bag for a more realistic picture of its ability to keep you warm. For example, a bag rated for 30°F should only be used in temperatures that never drop below 40°F. On the other hand, don't think you'll be comfortable in a 10° bag when it's a 70° night. People in warmer climates should buy bags with higher temperature ratings.
The table below offers some rough guidelines for selecting a sleeping bag with the right comfort rating.
| Sleeping Bag Use | Bag Comfort Ratings |
| Summer/Indoor | +40°F or higher |
| 3-Season Bag (Spring through Fall)/Summer High Altitude | +15°F to +40°F |
| Winter Camping | -10°F to +15°F |
| Polar/Extreme Alpine | -10°F or lower |
Your metabolism, blood circulation intensity and gender are all essentially uncontrollable factors that affect your body warmth. However, you do have control over a few things besides sleeping bag selection in your effort to stay warm when sleeping outside. By placing a sleeping pad or some other insulator between you and the ground, you can greatly increase a sleeping bag's ability to warm you. Also, being inside a tent or some other shelter to prevent wind chill can make you feel a full 10° warmer (and that's assuming there's only a light breeze!). Wearing a base layer and a hat can also bump up your warmth in a sleeping bag, as long as they're not damp.
Easily the most popular bags in the backpacking world, mummy bags are a must for cold nights and high altitudes. They may seem overly snug, but you'll appreciate that cozy, warm fit during a night when the mercury plummets. Mummy bags are widest at the shoulders and taper down to a narrower head and footbox.
Mummy bags are:
Rectangular bags offer more room to change positions during the night, but create a lot more air space that your body needs to heat up. In a nutshell, rectangular sleeping bags are:
Semi-rectangular bags, or "hybrids," fall somewhere in between mummy bags and rectangular bags: These sleeping bags are:
Bivy sacks (short for "bivouac sacks") are waterproof breathable sacks that envelop your sleeping bag to protect you in wet or windy conditions. When you're stuffed inside a bivy, it's like having a tent wrapped only around your bag. Essentially these are ultralight backpacking/ mountaineering shelters, and are also great for keeping the weight down on overnight cycling excursions.
Originally designed primarily for emergency survival situations, bivy sacks have become more popular with extreme minimalists who cover a lot of ground and need to lighten their load. Also, if you really love being able to see the stars as you fall asleep, these may be a better option than a tent.
Modern bivy sacks usually have a totally waterproof, reinforced bottom similar to a tent floor, with a lighter waterproof breathable fabric on top. "Bivy shelters" are a slight variation of bivy sacks. They provide an enclosed "mini-tent" around your head to totally block out bad weather, insects, etc.
Overbags are used in conjunction with your sleeping bag to provide a little extra insulation and protection from wind and water. They tend to be less-protective than bivy sacks, and are used more for supplemental warmth in very cold weather than as a total shelter.
Women's sleeping bags are narrower at the shoulder and wider at the hip than unisex sleeping bags, to prevent too much air circulation. Women's sleeping bags may come in various sizes (i.e., short, regular or long) to fit all heights. Also, women's bags usually offer extra insulation at women's "cold spots," namely the footbox and torso. Women tend to produce less heat than men, so they may need a sleeping bag with a lower temperature rating than men for use in the same conditions.
For a complete list of women-specific outdoor products and descriptions of each, check out our Women-Specific Gear Guide.
As a general rule, buy a long sleeping bag if you are over 6' tall (up to 6'6"). You'll find specific height information on every sleeping bag sold by Sierra Trading Post, which should make it easy to find the right bag length.
A high-quality sleeping bag's outer shell is usually made of nylon because of its lightweight durability. Nylon bags are either silky nylon taffeta or slightly more durable (but perhaps less smooth) ripstop nylon, which has extra-sturdy threads woven into the fabric in a crosshatch pattern. Some nylon shells utilize a very thin, highly breathable laminate like Gore-Texr's water-resistant DryLoftr or Sierra Designs' fully waterproof DryzoneT, which may come in handy if you experience a wet weekend.
Less-expensive bags may be constructed of polyester instead of nylon, which is fine if you are an infrequent camper and won't put lots of miles on the bag. Also, most of the less-expensive rectangular bags are crafted solely from cotton. Cotton is easy to care for, very breathable and won't stick to your skin, making cotton bags good for hot-weather car camping or children's sleepovers, but not much else.
The inner lining of a sleeping bag will most likely be nylon or smooth polyester. Cotton sleeping bags will have a cotton or flannel lining, though, and some fancier mummy bags may have a silk lining. Silk is very comfortable but less durable then nylon or polyester.
"Fill" refers to the insulation in a sleeping bag. There are three main types of insulation found in sleeping bags: down, synthetic (usually polyester) and cotton.
Down comes from the fluffy underfeathers of waterfowl - usually geese. All down products are rated by "fill power," which describes the loft (or volume) a given amount of the down occupies. A higher fill power means more volume occupied and thus more warmth; this rating can range in sleeping bags from as low as 400 fill power all the way up to supreme-quality 800 fill power. Compared to other fills, down:
Synthetic fill is basically formed from composite threads bunched into dense clumps. Usually made from polyester fibers, synthetic fill:
Check out our complete guide to Down vs. Synthetic Insulation for more information about the properties of these two sleeping bag fills.
Cotton fills are found in only the least expensive rectangular sleeping bags. Cotton-filled sleeping bags are acceptable for indoor sleeping or car camping in warmer weather, but never acceptable in the backcountry because of cotton's heaviness, its tendency to soak up water and its loss of heat-retaining abilities when wet.
If you have the money, down sleeping bags are generally best unless you plan to frequent wetter conditions. If you're new to camping, on a tight budget or live in a rainy climate, go with a synthetic fill. And remember that you get what you pay for. Department store bags may be inexpensive, but they're cheaply made and have many cold spots along the stitching. By comparison, better sleeping bags have some form of baffled construction to prevent cold spots. Stick with a name-brand bag by a manufacturer that will stand behind its product.
By taking good care of your bag, you may not need to replace it for a decade or more. Follow these tips to make your bag last:
Although there is a lot of information in this guide, it's really quite simple to pick a sleeping bag. Just follow these four steps:
