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Sleeping Bags for Backpacking: How to Choose

a backpacker tucking into their sleeping bag

This article helps you choose the best sleeping bag for backpacking, so you stay warm and comfortable despite the chill (or perhaps bitter cold) of a backcountry night. (Not a backpacker? Read Sleeping Bags for Camping: How to Choose.)

Differing from car-camping sleeping bags, most backpacking sleeping bags are mummy-shaped, lightweight and pack compactly.

When deciding how to choose a sleeping bag for backpacking, consider these three main decision points:

  • Temperature rating: Choose a sleeping bag rated for the typical temperature range you plan to backpack in. You can always add a liner for warmth or unzip the bag if you’re too warm.
  • Type of insulation: Choose from down, synthetic or a combination of the two. Each type of insulation has its pros and cons, explained below.
  • Weight vs. roominess: When backpacking, you want to keep weight low. For some, low weight overrides roominess. For others, having a roomy bag for a good night's sleep is worth a few more ounces.
  • Features: Consider the extras that make your bag work best for you, including types of zippers, draft collars, hood styles and more.

Sleeping Bag Temperature Ratings

If you’ve done any camping, you may have a sense for whether you sleep cold or warm, no matter the time of year. Keep in mind that your metabolism, sleepwear and use of a tent can all affect your sleep comfort.

Here is a general guideline for choosing a bag based on seasonal use (though of course, summer temps in one region of the country may differ from another region):

Bag Type 

Temperature Rating (°F)

Summer

+32° and higher

3-Season

+10° to +32°

Winter

+10° and lower

Temperature ratings on bags are a guideline; use your best judgment when choosing a bag to meet your needs.

How sleeping bags are rated: You may notice an “EN tested” tag on many 3-season backpacking sleeping bags. This stands for the European Norm (EN) 13537 testing protocol. The EN rating is internationally accepted as the most objective and dependable standard available, though not all bags use EN testing.

In EN testing, a bag is assigned two temperature ratings:

  • Comfort rating is the lowest temperature at which the bag will keep the average woman or "cold sleeper" comfortable.
  • Lower-limit rating is the lowest temperature at which the bag will keep a man or "warm sleeper" comfortable.

Everyone's body and sleep comfort is different, so EN ratings are merely a guideline to help you compare products.

(EN ratings are based on a sleeper wearing one long underwear layer and a hat, and sleeping on a single one-inch thick insulating pad.)

Sleeping Bag Insulation Types

Sleeping bag insulation (or "fill") doesn't provide any warmth by itself; it works by minimizing the amount of heat your body loses while sleeping.

Two basic insulation types are commonly used: down (which is usually water-resistant) and synthetic. Here's a brief overview:

Insulation Type

Key Benefits

Down

Lightweight
Easy to compress
Excels in cold, dry conditions

Synthetic

Quick-drying
Insulates when wet
Non-allergenic

Down Insulation (Goose or Duck) 

Down is an exceptional insulator, prized for being light, soft, easy to compress, long-lasting and breathable. It excels in cold, dry conditions or whenever saving weight and space are priorities.

Down is more expensive than synthetic fill, but it maintains its loft (which provides its heat-trapping ability) at a near-original state longer than synthetics. That makes down a good value over the long haul.

Fill power is the term used to measure down's ability to loft, and thus trap heat. It is calculated by how many cubic inches 1 ounce of down can fill in a testing device.

Higher-grade down, taken from more mature birds, requires fewer plumules to fill space and achieve a certain temperature rating. So a 700-fill-power down bag rated +20°F will be lighter than a 600-fill-power down bag rated +20°F.

Goose vs. duck down: While goose down has long been considered the pinnacle of all down, achieving fill-power ratings of 900 and potentially higher, duck down has largely taken over as the fill of choice in most down jackets and sleeping bags. Most down is a by-product of the meat industry, and more ducks are eaten than geese. As a result, duck down is more abundant and less expensive.

Down ethics: Some sleeping bag manufacturers are careful to use (or are moving toward using) only down that’s “traceable,” or ethically sourced. This down is from birds that are inspected throughout their lives from farm to factory. The aim is to ensure the ducks or geese are humanely raised and not force fed or live plucked.

Water-Resistant Down

Wet down turns into a soggy lump, losing its ability to retain heat. That’s why most sleeping bags now contain down that’s been treated at a microscopic level with a water-resistant application. It’s often called “hydrophobic” down.

Some testing shows that water-resistant down may dry out faster than non-treated down. However, if dunked in a stream or exposed to heavy rain, even treated down will get wet. Remember, it is water-resistant, not waterproof.

Synthetic Insulation   

Synthetic insulation (usually a type of polyester) is less expensive than down and dries much faster. Synthetics are nonallergenic and insulate even when wet. They are a good choice in damp climates and for casual or budget-minded backpackers.

The downsides are that a synthetic bag offers a little less warmth for its weight, is a bit bulkier when compressed, and its insulating power gets reduced each time it is stuffed into a stuff sack.

Some synthetic-fill bags feel soft and compressible, much like down. Others feel stiffer but may be more durable. Get a feel for both when you’re in a store and decide which you prefer.

Down/Synthetic Combination

Some bags now combine down and synthetic fill. These hybrids can provide the benefits of both materials and offset the imperfections. 

In some cases, the two types of insulations are blended together throughout the bag. In others, the durable synthetic may be on the bottom and lofty down on top. 

Sleeping Bag Weight and Shape

assortment of backpacking sleeping bag sizes, shapes, and lengths

Most backpacking bags are mummy-shaped, though some semirectangular and “peanut”-shaped bags are also suitable for the backcountry. Shop by comparing the shoulder and hip girth specs provided on REI.com product pages. Remember, it’s harder to keep warm in a bag that’s too roomy, but it can be nice to have wiggle room.

For less weight and more warmth: Choose a mummy bag with narrow shoulder/hip specs. You may, however, find it hard to get comfortable in these more restrictive bags.

For more comfort but a bit more bulk and weight:  Consider mummy bags with wide shoulder/hip specs or a semirectangular bag, especially if you have a broad frame or are a restless sleeper.

Sleeping Bag Length    

Most adult sleeping bags come in Regular or Long, though you might be able to find a few bags marked as Short (or Petite) or X-Long. These sizes differ depending on gender and manufacturer. The best way to choose the correct bag length is to review the product specs that list the person’s height a bag “fits up to.” A bag that’s too long for you may leave you with cold feet.

Women-specific Sleeping Bags

Women-specific bags are designed to fit a woman's contours. When compared with men's bags, they’re shorter in length (usually designed to fit someone up to 5'6" in height), narrower at the shoulders and wider at the hips. Often, there’s extra insulation in the upper body and/or footbox.

Note: Smaller women may find that some youth bags can offer a comfortable fit. However, these bags may not offer all the performance features and equivalent temperature ratings of an adult bag.

Sleeping Bag Features

assortment of sleeping bag features

Zipper compatibility: Many backpacking bags can be zipped together for sleeping by couples. Just know that mating two bags creates gaps inside, so it's a less efficient way to stay warm. You can mate any two sleeping bags if:

  • One bag has a "right-hand" zipper and the other a "left-hand" zipper.
  • 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 3/4-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.

It's also OK to mate bags of differing comfort ratings. You can arrange it so the warmer bag covers the colder sleeper.

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. Some hoods are designed to lie flat when the bag is unzipped and used as a quilt. Ultralight bags may save weight by doing away with a hood altogether.

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

Draft collar (or neck baffles) and face mufflers: Usually found on bags rated for colder weather, these are insulated baffles around your head and neck that prevent body heat from escaping and cold air from seeping in.

Differentiated cords: By feel in the dark, you can tell which cord loosens or tightens your hood and which cord adjusts your neck opening.

Stash pocket: This keeps small items, such as your phone, watch or glasses, close at hand. Pocket locations can vary by model.

Pad loops: These sewn-in straps let you secure your sleeping pad directly to your sleeping bag so you won't roll off. You can also hang your sleeping bag by way of these loops to store it.

Trapezoidal footbox: This design adds 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. The extra space also reduces the tension your feet put on the bag, which helps the insulation last longer.

Pad sleeve: Some sleeping bags eliminate the insulation on the bottom and replace it with a sleeve or attachments for an insulated sleeping pad. This bag design reduces overall pack weight and compresses smaller than conventional sleeping bags.

Sleeping Bag Construction

Basically, a sleeping bag consists of three parts: an outer shell, insulation and lining. While these are not key considerations for most backpackers, there are a couple things to note.

Shell and Lining

The outer shell of a sleeping bag is typically made of durable ripstop nylon or polyester. Most high-quality bags have waterproof, breathable shells (or partial shells); others are treated with a durable water repellent (DWR) finish that causes water to bead up rather than soak in. A waterproof or DWR-treated shell helps your bag stay dry if it touches the wet sides of your tent or you’re sleeping under the stars on a dewy night.

The inside lining of a sleeping bag is usually polyester or nylon taffeta. It’s soft for comfort and breathes well in order to let body moisture evaporate. 

Construction Techniques

Insulation is held between a bag's outer shell and inner lining by several techniques. The goal is always to ensure an even distribution of insulation.

Down bags either feature box-style baffles to hold the down in place for ultimate warmth, or all the layers are sewn-through (more typical on ultralight bags and not as warm).

Synthetic bags feature sheets or pieces of insulation, stitched to the shell and lining in a variety of methods. If warmth is your goal, avoid bags with many places where heat might escape.

Sleeping Bag Accessories and Care

backpacker stuffing sleeping bag into stuff sack

Most quality sleeping bags come with a stuff sack for use on the trail, and a large cotton bag for storing your sleeping bag in. Down sleeping bags in particular need to be stored in a roomy bag or hung by foot loops in a closet so the down can “breathe” and not lose its loft.

For more tips, see our article on Sleeping Bag Care.

Ultralight Backpacking Options

With a growing customer interest in ultralight backpacking, some manufacturers are creating alternatives to traditional sleeping bags. A backpacking quilt (usually down-insulated) or hoodless sleeping bag can be a lighter-weight option to consider.

While not necessarily lighter, some “bed style” backpacking sleeping bags feature an oval opening over the torso area with an attached, adjustable comforter. Other bags may have a top layer that’s removable. Both styles offer versatile comfort in a wide range of temperatures.

Contributing expert: Valerie Loughney is the sales lead of the REI Silverdale camping department and the in-store instructor for camping, cooking, backpacking and hiking classes. An avid backpacker for the past 16 years, she loves getting outside to explore nearby Mount Rainier and Olympic national parks as well as parts of Europe and Asia.

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