If you’ve ever shopped for sleeping bags, you probably noticed that a temperature rating (a.k.a. comfort rating) usually appears in the product name. (Example: Marmot 20°F Kenosha Down Sleeping Bag). Sleeping bag temperature ratings are tested by the manufacturer, either according to their own set of standards or in accordance with EN 13537 standards.
Manufacturer Standards for Sleeping Bags
When a company uses its own standards to measure a sleeping bag's temperature rating, that rating is often the coldest temperature a sleeping bag is designed to be used in (and hopefully still keep a person warm). However, not all companies use the same standards or testing methods. Also, different people have different comfort zones. What one person considers "warm" may be too cold for another person.
Unless you wear warm clothing at night, consider adding 10 degrees to the factory temperature rating of any sleeping bag. For example, a bag rated for 30°F should be used in temperatures of 40°F or warmer. If the temperature gets down to freezing, you might not get hypothermia, but you might not be warm and cozy either, unless you add some additional layers of clothing. Again, everyone’s comfort level is different. The chart below offers general guidelines for choosing a sleeping bag according to manufacturer comfort ratings:
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
EN 13537 Standards for Sleeping Bags
EN 13537 is a relatively new, three-part temperature rating system that has been used in Europe for several years. Recently, this system has been adopted in the United States by some brands. However, it's still an optional rating system, so not all manufacturers are required to use it. Sleeping bags that feature an EN 13537 rating are assigned three distinct temperature ratings according to a standardized laboratory test. Keep in mind that this rating system presumes that a user will be sleeping on a one-inch thick sleeping pad, will wear top and bottom base layers, and will also wear an insulating cap or beanie. The advantage to the EN 13537 system is that it offers multiple temperature ratings, which make it easier for a customer to choose an appropriate sleeping bag. This system provides three separate ratings:
- Comfort rating is primarily geared toward women and people who tend to sleep a little colder. This rating presumes that the user will sleep in a relaxed, supine position. If you tend to feel chilly easily at night, choose a sleeping bag based on this EN 13537 rating.
- Lower limit rating is primarily geared toward men and people who tend to sleep a little warmer. This rating presumes that the user will sleep in a curled position. If you consider yourself to be a warm sleeper, choose a sleeping bag based on this EN 13537 rating.
- Extreme limit rating is a survival rating only that designates the temperature at which a sleeping bag may or may not help prevent hypothermia. In other words, the sleeping bag may keep a person alive overnight at this temperature, but the person will most likely not be warm or comfortable.
How to Shop on Our Website
When shopping for sleeping bags on our site, you may notice that there is only one temperature rating provided in the product name. If a men's sleeping bag has an EN 13537 rating, we use the lower limit rating. If a women's sleeping bag has an EN 13537 rating, we will use the comfort rating. The full temperature rating can be found by clicking on the spec tab in the product description. When a sleeping bag doesn’t have an EN 13537 rating, we use the manufacturer's temperature rating.
Tips for Staying Warm
- Your metabolism, circulation, muscle mass, body fat percentage and gender are all factors that can affect body warmth. Although you can’t change many of these factors, you can maximize your chances of staying comfortable by always using a sleeping pad and adequate shelter. Sleeping pads are not only designed to provide cushioning; they also provide an insulating buffer zone between you and the cold earth.
- For cool weather, wear long underwear inside your sleeping bag to keep you warmer at night. This also keeps your bag cleaner and free of body oils. In colder conditions, it's also a good idea to wear warm socks and a lightweight winter cap.
- Always pull your bag out of the stuff sack at least 30 minutes or an hour before it's time to go to sleep, especially if it's a down sleeping bag. This will give your bag time to fully restore its loft before you bed down for the night.
- Another good trick for cold weather camping is to fill a water bottle with hot water, put the hot water bottle inside a sock (make sure the bottle cap or lid is sealed tightly first) and place it at the bottom of your sleeping bag. It won’t last all night, but it will help keep your feet toasty for a few hours.
Now that you have an understanding of sleeping bag temperature ratings, the next thing you'll have to consider is what kind of sleeping bag to buy. Most sleeping bags can be divided into three primary categories: mummy bags, rectangular bags and semi-rectangular bags, also called hybrid sleeping bags.
When it comes to keeping you warm and protected from the elements in the great outdoors, no other sleeping bag can compete with the mummy bag. When the mercury plummets, this style of bag is specifically designed to maximize warmth with its snug-fitting design. Of course, some people find this design to be a little restrictive. However, there are several benefits to using a mummy bag in the great outdoors:
- Mummy bags are the best choice for cold weather because their shape creates less dead air space.
- All mummy bags include an insulated hood for added warmth.
- Mummy bags are typically lighter than comparable rectangular bags because they use less material.
Rectangular Sleeping Bags
Unlike mummy bags, rectangular sleeping bags offer more interior space to move around and change positions during the night. Many people find this design much less restrictive and more comfortable. However, a rectangular design creates more dead air space that your body needs to heat up, which makes these bags much less warm than comparable mummy bags. Rectangular sleeping bags are good warm-weather bags, but much less ideal for cold weather. Below are some other things to consider when choosing a rectangular sleeping bag:
- Rectangular sleeping bags are ideal for sleepers who like to feel less restricted and move around a lot at night.
- Most rectangular bags are less expensive than comparable mummy bags.
- Rectangular bags tend to be heavier and bulkier than mummy bags, making them a poor choice for backpacking.
- Rectangular sleeping bags are not ideal for very cold conditions.
Semi-Rectangular Sleeping Bags
Semi-rectangular bags, sometimes called hybrid sleeping bags, fall somewhere in between mummy bags and rectangular bags. These sleeping bags are wider at both the shoulders and hips, but tapered down to the head and footbox. Most are hoodless. Semi-rectangular bags tend to be slightly heavier and bulkier than comparable mummy bags, but are also roomier. Most are lighter and less bulky than comparable rectangular bags. If you find a mummy bag too restrictive but need more warmth than a rectangular bag can provide, a hybrid sleeping bag may be a good alternative.
Women's Sleeping Bags
Women's sleeping bags are usually slightly narrower at the shoulder and slightly wider at the hips compared to men's and unisex sleeping bags. This design helps create a more comfortable fit for most women and also minimizes dead air space. Some women's sleeping bags also offer additional insulation at common "cold spots," such as the footbox and torso. Aside from these factors, there is very little difference between a women's sleeping bag and a unisex bag.
A Note on Sleeping Bag Sizes
Many sleeping bag models come in two sizes: regular and long. As a general rule, you should only buy a long sleeping bag if you're over 6' tall (up to about 6'6"). If you're under 6' tall, a regular sleeping bag should be adequate. Some sleeping bags also come in short, and some brands make sleeping bags designed for children, which are even smaller. To find specific length, girth and weight information on all of our sleeping bags, simply click on the 'specs' tab in the product description.
Sleeping Bag Shell & Lining
The outer shell of a high-quality sleeping bag is usually made of nylon, which is both lightweight and durable. Nylon bags are typically either made from smooth nylon taffeta or slightly more durable ripstop nylon. Some nylon shells even utilize a waterproof breathable laminate or membrane like Gore-Tex® to provide additional protection in harsh weather conditions. The lining of most sleeping bags is made of polyester, which is breathable and soft against the skin.
Less-expensive sleeping bags may be constructed with a polyester shell, which is suitable if you’re an infrequent camper and won't put lots of miles on your bag. Polyester shells aren’t as durable as nylon shells, but are still lightweight and breathable. Some inexpensive rectangular bags may be manufactured with a cotton shell and lining. Cotton is easy to care for, breathable and comfortable in mild conditions. However, always avoid using a sleeping bag made of cotton in wet conditions because this material dries very slowly once it becomes damp.
Types of Sleeping Bag Fill
Fill refers to the insulation found inside a sleeping bag. There are three primary types: down, synthetic and cotton.
Down fill 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 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 800 fill power. Below are some key advantages of down fill:
- Down is the lightest fill you can buy and has the highest warmth-to-weight ratio. This means that a 30°F down-filled bag will almost always weigh less than a 30°F synthetic-filled bag.
- Down is the most compressible fill and offers the greatest longevity. In other words, down insulation can be compressed regularly and will still expand to provide substantial warmth for many years. Synthetic fills tend to lose more loftiness over time. Down fill also compresses more than synthetic fill. This means that a fully compressed down sleeping bag will usually take up less space inside a backpack compared to a comparable synthetic sleeping bag. (Note: Never compress your sleeping bag for long-term storage. Always store your bag in a larger storage sack rather than in a compression sack.)
Synthetic fill is usually created from polyester fibers. High-quality synthetic fills are designed to emulate the loft of natural down insulation. However, no synthetic fill can quite match the warmth-to-weight ratio of down. Below are some key advantages of synthetic fill:
- Most synthetic fills are less expensive than down.
- Synthetic fill is hypoallergenic and ideal for people who are allergic to down.
- Unlike down, which loses most of its insulating properties when wet, synthetic fill still provides some degree of insulation after becoming wet.
Take a look at our Down vs. Synthetic Guide for more detailed information about the properties of these two sleeping bag fills, or check out the video below:
Cotton fill is found in only the least expensive sleeping bags. Cotton-filled sleeping bags are acceptable for indoor sleeping or car camping in warm, dry weather, but are never a good choice in the backcountry. Cotton fill is heavy, absorbs water quickly, dries slowly and loses its insulating properties when wet.
Buying for Your Budget
If you have the money, down sleeping bags are generally the best, unless you plan to camp in very wet conditions. However, a down bag with a waterproof breathable membrane is another good option for wet and cold conditions. If you're new to camping, on a tight budget and/or live in a very wet climate, consider going with a synthetic sleeping bag. Keep in mind that you get what you pay for. Inexpensive department store sleeping bags may be easy on the budget, but they're cheaply made and won’t provide the same level of warmth and durability as quality bags from reputable brands. By comparison, better-quality sleeping bags typically have baffled construction to prevent cold spots and are designed to last. To get the best bang for your buck, stick with sleeping bags from name-brand manufacturers that stand behind their products.
If you take good care of your sleeping bag, it can last for many years. Of course, how long your bag lasts largely depends on how often you use it. If you only camp out once or twice a year, your bag could last for decades. If you spend four months backpacking across Europe, on the other hand, your sleeping bag will probably wear out much sooner. To get the most longevity out of your sleeping bag, follow these simple tips:
- Always air out and thoroughly dry your bag after every use.
- If you used your bag for more than a few nights, consider laundering your bag.
- Follow the care instructions when washing your sleeping bag. These are usually listed on the tag. Most sleeping bags should be hand washed with mild detergent or washed in a front-loading washer on gentle cycle. Always tumble dry on low heat.
- Store your bag in a cool, dry place and don't leave it crammed into a compression sack, or it will eventually lose loft and may permanently become less effective. Most bags come with two sacks: a small one for camping and backpacking, and a larger one for long-term storage. If your bag didn't come with a larger storage bag, you can simply use a trash bag. This will also help keep out bugs. Just make sure your bag is completely dry before storing it.
- Never pack away a wet sleeping bag for longer than it takes to drive home from your destination. Hang it out to dry as soon as you get home. If the bag has a musty or funky odor after being dried, consider washing it.