How To Buy a Sleeping Bag

Some of the most cathartic moments you experience during multi-day wilderness escapes happen when you slip into your sleeping bag beneath the stars. The blissful warmth that engulfs your sore body as you lie your head down simply cannot be replicated with Egyptian cotton sheets. But that’s only if you bring the right sleeping bag. If you don’t, you run the risk of spending the night in misery, struggling like a fish out of water—a thrashing, shivering disaster. The difference between comfort and misery outdoors comes down to making the right buying decision. Here are a few pointers to help you choose the best sleeping bag for your needs.

Temperature Ratings: Sleeping bags are broadly categorized by temperature rating, meaning the temperature listed is the coldest that your bag can handle comfortably. Be sure to check if the temperature rating follows the EN 1357 standard, which is used by many companies to provide uniform ratings.

If the temperature rating is not based on EN 1357, it might be an arbitrary designation by the company that you may or may not agree with. Even if the EN 1357 standard is followed, temperature ratings are subjective. While one person may sleep comfortably in a 20-degree bag at 10 degrees, another may freeze in the same bag at 30 degrees.

If you get cold easily or have sweaty hot flashes all night, you will want to keep in mind that these ratings are based on average comfort levels. Wet/humid climates tend to feel colder (when it’s cold) and hotter (when it’s hot) then the same temperature in dry climates. Also keep in mind that the ratings are based on the user wearing a simple base layer. The temperature range of a bag can be extended by wearing heavy clothing inside the bag.

Season ratings: Additionally, some sleeping bags have a season rating in addition to the temperature rating to give you an idea of its best use.

Summer bags: Should not be used where the temperature dips below freezing.
Three-Season bags: Can sometimes handle below-freezing temperatures, but nothing too frigid.
Winter bags: These are excellent for keeping warm when there is a blizzard outside your tent, but not ideal for other seasons unless used as a blanket.
Extreme bags: For when it’s really cold. For example: high in the Himalayas or on an ice sheet in Antarctica.

Weight: The weight of your bag depends largely on what type of material it is filled with (more on that later). Additionally, you will be sacrificing weight for space. Roomier bags are heavier than their form-fitting counterpart.

If you are car camping, weight might not be an issue. However if you’re going on an extended backpacking trip, then you’ll want the lightest bag comfortably possible.

Insulation Type: The material inside the bag used to keep you warm is called fill. There are three main types of fill:  Down, Synthetic, and Cotton.

Down: Made from the undercoating of young birds, this natural material is a fantastic insulator. It’s lightweight, compressible, and retains volume after getting packed and repacked many times.  However, it does have some drawbacks:

    • It is more expensive than synthetic fill
    • Loses ability to insulate when wet (Water resistant down combats this to an extent)
    • Takes a long time to dry when wet
    • Requires a dependence on farming waterfowl

Water resistant down: Technologies like DriDown (unique to Sierra Designs) and DownTek (a third-party supplier of water resistant down) treat down in a way that makes down more apt to wet climates. While a great innovation, it is more expensive.

Synthetic fill: Synthetic down is intended to copy the effects of down.  It’s usually made from polyester fibers and is a great alternative if price is a factor. Additionally they work much better in wet environments, drying out faster and repelling water instead of absorbing it.  However, synthetic fill does not pack well and has a higher weight-to-warmth ratio than a down bag with the same temperature rating.

Cotton fill: Cotton is a poor option. Cotton doesn’t have any properties that make it superior to the other two options except for price. It’s a poor insulator, does not pack well, and is dreadfully soggy when wet.

Fill Power: Not all down is created equal, and fill power helps you make a better decision based on your weight/volume expectations. The higher the fill rating, the lighter and more compressible your bag will be compared to one with a lower fill rating of equal temperature/warmth.

Over time, the fill power can decrease.  Washing your bag, especially with a few tennis balls, will help “fluff” the bag and bring the fill power back.

Shape: There are three main shapes for sleeping bags: rectangular, mummy, and hybrid. While largely personal preference, the shape also determines how well the bag can recirculate body heat.

Rectangular bags: Shaped just as the name implies. They are roomy, which in sleeping bag speak, also means bulky. Generally they zip all the way to the feet and can even be opened up to use as a blanket making them great for summer.  Some bags can even be zipped together for multiple bodies to share body warmth.

Mummy bags: These are tapered at the feet, and oftentimes include a hood, making mummy bags a better insulator than a rectangular bag. However sometimes it works too well and since zippers usually only goes halfway down the body, ventilating on warm nights can be a hassle for warm sleepers. On the other hand, the smaller volume of a mummy bag saves on weight making them more compactable.

Hybrid bags: Hybrids are a compromise between rectangular and mummy bags. They provide the roominess and ventilation of a rectangular bag, but are lighter and more packable and have a hood for cold nights.

Women specific bags: Women specific bags have wider seams at the chest and hip. Many companies make women specific bags.

Packability: A warm, roomy sleeping bag is not much use if it doesn’t fit in your backpack. Similarly, if space is not an issue (i.e. if car camping), then getting an expensive bag simply because it packs up small might not be the best use of your resources.

Packed Volume:  Some bags pack more tightly than others, which is important when you have limited space in your backpack.  Packed volume is a metric that helps gauge the size of your bag when packed. Most sleeping bag models will provide this, or the information can be found with a little bit of inquiry.

Containment: When packing your bag, there are usually two options to contain it: A stuff sack or compression sack. Cotton bags don’t really apply here since they are made to “fold and roll”.

Stuff Sacks: Stuff sacks allow you to quickly and easily “stuff” your bag into the sack with little regard for order. This is a good way to store your down bag, as it gives the down room to retain its shape over time. Pro tip: if down compressed for too long then it can take a long time for it to get it’s “fluffiness” back.

Compression Sacks: These can be cinched down and get the bag compressed to its smallest possible volume, giving you extra room in your pack for other fun supplies. Many compression sacks are waterproof. Keep in mind that down bags shouldn’t stay in compression sacks after the transport. Opt for a more voluminous sack when being stored.

With so many variables, finding the right sleeping bag can seem daunting. Often times the ideal bag is dictated by the price tag. But keep in mind that if you take care of your sleeping bag, it can last for many adventurous years. One day, slipping into your sleeping bag at the end of a hard slogged day in the elements, and you’ll be glad you did your homework.