How To Choose A Sleeping Bag

When choosing a sleeping bag for backpacking, consider these three main decision points:

  • Temperature rating: Choose a bag rated for the coldest temperature you expect to encounter.
  • Type of insulation: Choose from synthetic, down or a combination of the two. With a few exceptions, most down bags today use water-resistant down. Each type of insulation has its pros and cons, which are explained below.
  • Weight vs. roominess: When backpacking, you want to keep weight low without jeopardizing comfort or safety. For some, low weight overrides other concerns (durability, convenience, price). For others, weight is less important than having a roomy bag for a good night’s sleep. Most bags seek to strike a balance between these ideals.

Sleeping Bag Temperature Ratings

Most 3-season backpacking sleeping bags are rated for temperature by the European Norm (EN) 13537 testing protocol. The EN temperature rating is internationally accepted as the most objective and dependable standard available. In EN testing, a bag is assigned two temperature ratings:

  • Comfort rating (for women) is the lowest temperature at which the bag will keep the average woman warm.
  • Lower-limit rating (for men) is the lowest temperature at which the bag will keep a man, on average, warm.

EN ratings are based on a sleeper wearing one long underwear layer and a hat, and sleeping on a single 1″-thick insulating pad.

What Temperature Rating Should I Choose?

Here is a general guideline for choosing a bag based on seasonal use (though of course, seasonal temperatures can vary based on your specific location and conditions):

Bag Type  Temperature Rating (°F)
Summer Season +35° and higher
3-Season +10° to +35°
Winter +10° and lower


  • EN-rated sleeping bags can be expected to provide comfort to the given temperature, keeping in mind variables such as clothing, metabolism and use of a tent.
  • For non-EN-rated bags, go with a temperature rating lower than the lowest temperature you expect. For example, if near-freezing temps are expected, bring a 20°F bag instead of a 35°F bag. (Tip: On warmer nights, you can always use the double-zippers to vent an area by your legs. Or, simply drape the unzipped bag over you.)

Sleeping Bag Insulation Types
Sleeping bag insulation (or “fill”) doesn’t provide any warmth by itself; it works to minimize 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

Down Insulation (Goose or Duck)

Down is an exceptional insulator, prized for being light, 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 oz. 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 any bag rated +20°F with 700-fill-power down, no matter if its fill is duck or goose down, will be lighter than a +20°F bag using 600-fill-power down.

Duck Down vs. Goose Down

  • Top-end fill power: Duck down can achieve fill-power ratings no higher than 750 or 800. Premium goose down can reach 900 and potentially even higher ratings, but it’s quite expensive.
  • Durability: Goose plumules are typically larger than duck plumules and can potentially retain their lofting ability for a longer time. One manufacturer estimates the average lifespan of a goose down bag (at its original temperature rating) is 25 years vs. 20 years for a duck down bag.
  • Odor: Modern processing/cleaning techniques have reduced the possibility that duck down, when wet, can exude a gamey smell. It is conceivable, however, that people with a heightened sense of smell may still detect a slight odor from duck down no matter how clean or dry duck down is.

Water-Resistant Down

Moisture is the chief nemesis of down. Wet down becomes matted and flat, losing its ability to retain heat.

Proprietary technologies treat down at a microscopic level with a water-resistant application.

Manufacturer testing indicates down with a water-resistant treatment can withstand dampness created inside a bag through body vapor. The technologies are also believed to help damp down dry out faster and minimize (or perhaps eliminate) any odor caused when down gets wet.

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 considerably faster. Synthetics are nonallergenic and retain much of their warmth 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.

There is a long list of competing brand names for synthetic insulations, but a more relevant distinction is knowing whether a synthetic insulator is short-staple or a continuous filament.

  • Short-staple fills are the predominate choice. Their short strands of fine-denier filaments are densely packed to minimize heat loss. This makes these bags feel soft and flexible, much like a down bag, and allows for great compressibility. They are, however, a bit less durable.
  • Continuous-filament fills use a thicker continuous filament that is lofty, strong and durable. They have a stiffer feel and are less compressible than short-staple bags.

Down/ Synthetic Combination

Some manufacturers are building bags with combinations of water-resistant down and synthetic insulation. This hybrid construction can provide the benefits of both materials while limiting each material’s imperfections.

In some cases, the two types of insulations are blended together throughout the bag. In others, the insulation may be in different locations within the bag, for example, durable synthetic on the bottom and lofty down on top.

Weight vs. Roominess (Sleeping Bag Shape and Fit)

All true backpacking bags are mummy-shaped, though some semirectangular bags are suitable for the backcountry. Shop by comparing the shoulder and hip girth specs provided on product pages.

For maximum thermal efficiency and less weight: 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.

Women-specific bags are designed and engineered to fit a woman’s contours. When compared to men’s bags, they’re shorter in length, narrower at the shoulders and wider at the hips. Often, there’s extra insulation in the upper body and/or footbox.


Bag Length

Most adult sleeping bags come in sizes designated as Regular or Long, though you might be able to find a few bags marked as Short (or Petite) or X-Long. These size designations equate to different lengths depending on gender and manufacturer. Because of this, the best way to choose the correct bag length is to review the product specs which list the length a bag “fits up to.”

Note: Smaller women may find that some kids’ 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 Construction
Insulation can be held between a bag’s outer shell and inner lining by several techniques. The goal is always to ensure an even distribution of insulation.

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.


Down Sleeping Bag Construction

  • Box baffle: This durable approach features lightweight vertical baffle walls that connect the outer shell to the inner liner in a series of channels or chambers. This ensures an even layer of insulation and keeps down from shifting so you enjoy consistent warmth. Variations include trapezoidal and slant boxes, which are often used in the footbox.

  • Sewn-through: This weight-saving technique is often used on ultralight bags. The shell and liner are stitched together much like in a typical quilt. The downside is that this can allow cold spots at the stitched areas.

Synthetic Sleeping Bag Construction

  • Shingles: Shingles are cut pieces or sheets of fill stitched to both the shell and lining. They overlap each other somewhat like the shingles on a house to eliminate cold spots.

  • Layered: Most popular is the offset-quilt approach. This features two layers of continuous insulation where the top sheet is stitched to the outer layer and the bottom sheet is stitched to the lining. These layers are then offset to reduce cold air penetrating the quilted seams. Another version, known as quilted-through, is a sheet of insulation cut to fit the shape of the bag. The shell, insulation and lining are all sewn together with a single stitch line. This less-expensive technique is used only on warm-weather bags since it is prone to cold spots.

Shell and Lining

The outer shell of a sleeping bag is typically made of a ripstop nylon or polyester for durability. The shells of most high-quality bags are made from a waterproof breathable fabric, others are treated with a durable water repellent (DWR) finish. DWR causes water to bead up rather than soak through the fabric

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.

Sleeping Bag Features
Zipper compatibility: Many backpacking bags can be zipped together for sleeping by couples. Just know that mating 2 bags creates gaps inside, so it’s a less efficient way to stay warm. You can mate any 2 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: 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 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 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 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 improve longevity of the insulation.


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