How to Choose a Sleeping Bag for Backpacking

• What's Your Backpacking Style?
• Pick a Comfort Rating
• Women's Bags
• Insulation: Down or Synthetic?
• Sleeping Bag Construction
• Other Bag Features
• Sleeping Bag Liners
• Bag FAQs

For a relatively small amount of weight, a sleeping bag allows you to stay warm and comfortable despite the chill (or perhaps bitter cold) of a backcountry night. Backpacking bags can represent a fairly sizable investment, so take a few minutes now to learn how to pick the right one for you. Not a backpacker? Read our separate discussion of sleeping bags for family/base camping.

What's Your Backpacking Style?

When backpacking, you want to keep weight low, without jeopardizing comfort or safety. Individual views on comfort and weight, of course, can vary greatly. So REI divides core gear (bag, pack and tent) into 4 general categories. The goal: to help you build a gear system matched to your preferences.

• Minimalist: Low weight overrides all other concerns (comfort, durability and convenience).
• Ultralight: Gear for those willing to forego some conveniences to reduce pack weight.
• Lightweight: Traditional gear redesigned with new-generation, low-weight materials.
• Deluxe: For explorers who put a priority on comfort and convenience features.

Look for these classifications to help narrow your search when shopping at REI.

Pick a Comfort Rating

How Do Sleeping Bags Work?

Sleeping bags keep you warm by trapping and holding a layer of "dead" (non-circulating) air next to your body. This dead air is warmed by your radiated body heat, with the bag forming a barrier between this air and the colder ground or outside air. The less air space there is to heat, the faster you warm up and stay warm.

What Is a Comfort Rating?

A sleeping bag's temperature or "comfort" rating identifies the lowest temperature at which a bag will keep the average sleeper warm. When you hear a bag described as a "20-degree bag," it means that most users will remain comfortable if the air temperature drops no lower than 20°F. These ratings are based on the sleeper wearing a layer of long underwear and using a sleeping pad with the bag.

Are such ratings infallible? No. Humans all have different metabolic rates, and no industry standards exist that uniformly determine comfort ratings. Instead, each manufacturer assigns a rating based on its own research. Therefore, use these ratings as a guide, not a guarantee.

What Else Affects My Overall Warmth?

Besides a sleeping bag, the following factors influence your warmth and comfort.

• Sleeping pad: This insulates the space beneath your bag as well as adding cushioning. On some bags, the pad replaces the need for insulation on the bottom side of the bag. If sleeping on snow or frozen ground, we recommend using 2 pads.
• Tent: Using a tent or bivy sack traps a layer of dead air around you, warming it by up to 10°F.
• Metabolism: You might be a "cold sleeper" who prefers extra insulation when sleeping. Or maybe you are a "warm sleeper" who kicks off the covers at home.
• Gender: Women generally prefer slightly warmer bags than men.
• Clothing: What you wear inside the bag makes a difference. Long underwear and clean socks help insulate you while also keeping body oils off of your bag. A cap and neck gaiter help retain body heat. For colder-than-expected nights, a fleece jacket and pants can help.
• Hood: Sleeping bags with hoods can be cinched up on cold nights to help retain warmth.
• Hydration: Staying hydrated adds warmth. A warm drink before bed is a popular tip.

What Comfort Rating Should I Choose?

Select a bag with a comfort rating that is a bit lower than the lowest temperature you expect to experience. For example, if near-freezing temperatures can be expected, then choose a 20°F bag instead of a 35°F bag. On warmer nights, you can always vent a bag by using the double-zipper to open the area by your legs. Or, simply drape the unzipped bag over you.

Here's a general rule of thumb on comfort ratings:

Women's Bags

In the last decade or so, sleeping bag options for women have increased dramatically. These bags are specifically designed and engineered to match a woman's contours. When compared to standard bags, women-specific bags usually have the following characteristics:

• Shorter in length
• Narrower at the shoulders
• Wider at the hips
• Occasionally, extra insulation in the upper body and/or footbox

Insulation: Down or Synthetic?

Down

Down is the fluffy plumage that forms the undercoat of geese and ducks. This natural fiber is an extraordinary insulator. Premium down usually comes from geese, as their plumes offer a higher fill power. Fill power (or loftiness) refers to the number of cubic inches one ounce of down will displace. The higher the down's fill power, the less down is needed to achieve a given comfort rating. For example, a +10°F bag using 800-fill-power down will weigh less than a +10°F bag using 600-fill-power down. Because high-fill-power down is less plentiful, it usually comes with a higher price tag.

Down loses its insulating properties when wet, so any high-quality down bag will use a shell fabric treated with a Durable Water Repellent (DWR) finish. DWR allows water to bead up rather than soak through the fabric. In addition to DWR, a few specialty bags feature a waterproof/breathable coating so the bag can be used in wet climates.

Synthetics

Synthetic insulators (usually a type of polyester) retain much of their warmth even when wet, so they are a good choice in damp climates. They are quick-drying, nonallergenic and (in high-end bags) almost as light as down bags. The downside is that a synthetic bag offers a little less warmth for its weight, plus its insulating power gets reduced each time it is stuffed into a stuff sack. There is a long list of competing brand names for synthetic insulations, which can make shopping confusing. A more relevant distinction is knowing whether a synthetic insulator is short-staple or a continuous filament.

• Short-staple fills (e.g., PrimaLoft®) are the predominate choice. These usually feature short strands of a fine-denier filament (about 1 denier), which is sort of a synthetic version of down feathers. This makes the bag feel soft and flexible. It also allows for a highly compressible bag.
• Continuous-filament fills (e.g., Climashield®) use a thick (usually 3 denier) continuous filament that, when used in a shingle construction, is lofty, strong and durable. They have a stiffer feel and are less compressible than short-staple bags.
• Hybrid bags, currently offered only at REI, seek to combine the best characteristics of both short-staple and continuous-filament fills. They use multi-denier fibers (3 denier and less than 1 denier) to trap both convective and radiant heat loss.

An emerging trend in synthetics is known as eco-fill (e.g., Climashield® Green). A percentage of these fills uses recycled polyester, which helps reduce the amount of raw materials needed.

Which Insulation Is Right for You?

Choose a down bag if you want superior warmth, compressibility and durability. Though initially more expensive, down's superior durability makes it a good value over the long haul. You might want to avoid down, however, if you camp mostly in damp, rainy climates.

Choose a synthetic bag if you want both good performance and a lower price tag. Short-staple synthetic bags offer excellent compressibility, while continuous-filament synthetic bags are lofty and more durable. Synthetic fills are usually the better choice for wet climates.

Comparative Weight Guide

Use the following chart as a ballpark guide for your sleeping bag's weight. The weights indicated are an approximate goal for your bag weight depending on the type of bag and its intended use.

Sleeping Bag Construction

Shape and Fit

The shape of a bag certainly affects your sleeping comfort. All true backpacking bags are mummy-shaped, but some camping bags can double for use in the backcountry (these roomier bags are sometimes called barrel bags or semi-rectangular bags). To compare sizes, look for the shoulder and hip girth specs provided on REI.com product pages or the in-store sleeping bag product-info guide. Rules of thumb:

• For maximum thermal efficiency and less weight, choose a mummy bag with narrower shoulder/hip specs. Some folks, however, find it hard to get comfortable in these more restrictive bags.
• If you have a broad frame or are a restless sleeper, consider mummy bags with larger shoulder/hip specs or barrel bags for greater comfort. These bags are a bit bulkier and heavier, though.

Baffles and Shingles

Between a bag's outer shell and inner lining, a bag's insulation is held in place by a system of baffles. The goal of baffles is to ensure an even distribution of the insulating fill and avoid cold spots. There are many ways that manufacturers accomplish this.

Down bags typically use the following baffle constructions:

• Box: This time-tested approach is strong and keeps down from shifting so you enjoy consistent warmth. A common variation of this is called a trapezoidal box.
• Slant box: Another variation on the box theme, this one uses slanted baffles to avoid cold spots at stitch-points. The downside is the baffles can eventually flatten and impair insulation, so its use is declining.
• Sewn-through: This weight-saving technique is used on ultralight bags as their lesser amounts of insulation preclude the need for a baffle.

Synthetic bags typically use one of these shingled constructions:

• Z-baffle: REI's proprietary system features 2 insulations: shorter baffles of large-denier fibers to retain your body heat, and longer baffles of fine-denier fibers to reflect body heat back to you. This triangulated structure increases shell and lining support for excellent loft and durability.
• Layered: This efficient approach varies the amount of insulation by area of the bag. (e.g., more on top, less on the bottom) so you get warmth where you need it.
• Offset-layer: Two layers of continuous insulation are offset to reduce cold air penetrating the quilted seams. Simple, but effective.
• In the round:This is another proprietary REI construction that wraps vertical baffles around the all-important head and foot sections.

Shell and Lining

The outer shell of a sleeping bag is typically made of a ripstop nylon or polyester for durability. Any high-quality down bag—and many synthetic-fill bags as well—feature a shell fabric treated with a Durable Water Repellent (DWR) finish. DWR is the stuff that allows water to bead up rather than soak through the fabric

The inside lining of a sleeping bag, on the other hand, should promote the dispersal of body moisture, so DWR is not used here.

Tip: How can you tell if a shell has a Durable Water Repellent (DWR) treatment? Rub a wet cloth across the surface of a bag. If the water beads up, then it has DWR.

Bag Length

Note: The North Face offers a few bags in the X-Long size for campers up to 6'8"tall.

Other Bag Features

Zipper compatibility: Many backpacking bags can be zipped together for sleeping by couples. You can mate any 2 sleeping bags IF:

• One bag has a "right-hand" zipper and the other a "left-hand" zipper. A right-hand zipper means the bag opens and closes to your right when you are lying in the bag on your back.
• The zippers are the same size. Most brands use either a size #5 or #8 zipper, so these sizes need to match.
• The length of the zippers is compatible. Some bags have 1/2-length zippers, others use ¾-length zippers. You can still zip together bags with different zipper lengths, but you may have cold spots where the zippers don't match up.
• In the round: This is another proprietary REI construction that wraps vertical baffles around the all-important head and foot sections.

It's also OK to mate bags of differing comfort ratings. You can arrange it so the warmer bag covers the colder sleeper. Just be aware this creates bigger gaps inside, so it's a less efficient way to stay warm.

Hood: You can lose a significant amount of heat through your head, so virtually all backpacking bags include a built-in hood. When cinched with a drawcord, a hood prevents heat from radiating away. Some hoods offer a pillow pocket that you can stuff with your clothing to create a pillow.

Draft tube: This is an insulation-filled tube that runs alongside the bag's main zipper. It's designed to keep warmth from escaping between the zipper coils.

Draft collar: Usually found on bags rated 0°F or colder, these are insulated tubes positioned just above the shoulders to prevent body heat from radiating up and out of a bag.

Stash pocket: This is handy for keeping small items such as your MP3 player, watch or glasses close at hand. Pocket locations can vary by model, so check it out to see if it works for your needs.

Pad loops: These sewn-in straps provide an attachment point so you can secure your sleeping pad directly to your sleeping bag so you won't roll off.

Trapezoidal footbox: This design creates added space in the foot area to allow a more natural sleeping position for your feet. This is most useful if you sleep on your back rather than on your sides. A secondary benefit is that the extra space reduces the tension your feet put on the bag, which helps improve longevity of the insulation.

Sleeping Bag Liners

Sold separately, a sleeping bag liner is primarily used to help keep your mummy bag clean and thus make it last longer. (Note: Rectangular sleeping bag liners are commonly called "travel sheets.") A bag liner also adds anywhere from 5° to 15°F of extra warmth to your sleeping bag, depending on the liner material. In hot climates, you can use a bag liner or travel sheet by itself and forgo the sleeping bag.

You typically have a variety of bag-liner material choices:

• Silk: Very lightweight (about 5 oz.). Silk helps insulate in cold weather but is absorbent and breathable in warm weather. Price: moderate to expensive.
• Cotton: Strong, durable and absorbent, but not the lightest or most compact. Price: economical.
• Fleece and microfleece: Warmer (adds up to 12°F) and a bit heavier choices. Fleece is soft, moisture-wicking and quick-drying, but the mid- and heavyweight varieties tend to be bulky. Price: moderate.
• Synthetics (CoolMax and MTS®): Moisture-wicking and breathable, which makes these great for humid conditions. Has a bit of stretch, too. Price: moderate.
• Insulated (Thermolite): This adds up to 15°F of warmth thanks to its hollow-core fiber insulation. It also dries 50% faster than cotton. Price: moderate to expensive.

Sleeping Bag FAQs

Q. Does a sleeping bag's comfort rating decrease with use?

A. Yes. Bag makers generally agree that a sleeping bag will lose some of its warmth over time. The exact amount lost depends on how often the bag is used and how well it is stored.

Q. Is this loss of insulation equally true for down and synthetic fills?

A. No. Down plumules break down at a much slower rate than do synthetic fibers. In fact, down bags are known to last for 20 to 30 years if cared for properly. Synthetics are made from either or short staples or continuous strands of fill. The continuous-filament variety is the stronger and more durable of the two, especially if its used in a shingle construction. Again, the proper use and storage of any bag are the key factors in its durability.

Q. Why do fills eventually lose the ability to insulate after being compressed?

A. Compression can cause synthetic fibers to actually break in half—think spaghetti noodles—and the broken strands lose the ability to trap air and keep you warm. The feathers in down bags are more resistant to breakage, but they too will break down if stored tightly under prolonged pressure.

Q. How do I keep from rolling off my sleeping pad at night?

A. Most sleeping bags now incorporate pad loops to help secure your sleeping bag to your sleeping pad. One bag maker, Big Agnes, uses a pad sleeve instead of pad loops to accomplish the same thing.

Q. Is there a right way to stuff your bag into its stuff sack?

A. Not really, but it's a bit more efficient if you start with the foot end of the bag first. This allows air to escape through the top opening and not be trapped when you are compressing the bag.

Q. Can a compression stuff sack be used with any sleeping bag?

A. Yes, this type of stuff sack works wonders to compress either a down or synthetic sleeping bag to its minimum size for more efficient packing.