How to Choose a Sleeping Bag Without Getting Talked Into Too Much

The right sleeping bag for most three-season backpackers is a 20°F down bag with 800-fill power — not the ultralight quilt, not the expedition -20°F bag, and not the synthetic bag unless you're regularly camping in sustained wet conditions.

Why most hikers buy the wrong sleeping bag

Gear shops sell sleeping bags by temperature rating extremes — the warmest bag available or the lightest weight. The result: backpackers who camp at 35–45°F buy a 0°F bag that weighs twice what they need, or they buy an ultralight quilt that leaves them cold because they didn't account for radiative heat loss without full coverage. The correct decision framework has three variables: lowest expected temperature, your personal sleep temperature (cold sleeper vs warm sleeper), and pack weight tolerance. Everything else — fill type, shell fabric, zipper configuration — is secondary to getting these three right. For what to layer inside the bag, see our [alpine layering guide](/how-to-layer-alpine-hiking).

Variable 1: Temperature rating — what the numbers actually mean

EN/ISO temperature ratings have three values: Comfort (the temperature at which a standard cold sleeper sleeps comfortably), Lower Limit (the temperature at which a standard warm sleeper sleeps comfortably), and Extreme (survival limit — not comfortable sleep). Manufacturers market the Lower Limit as the bag's rating. A bag rated 20°F is comfortable for a warm sleeper at 20°F — a cold sleeper needs a 10°F bag for the same comfort at 20°F. Know whether you're a cold sleeper (always need more layers than companions) and adjust the temperature rating by -10°F from the lower limit if you are.

Variable 2: Fill type — down vs synthetic

Down at 800+ fill power: the best weight-to-warmth ratio available, compresses to smaller pack size, lasts 10–15 years with care. Limitation: loses insulation when wet, takes hours to dry. Wet down retains approximately 20% of dry loft. Synthetic fill: retains 70–80% insulation when wet, dries faster, costs less, better for consistently wet climates. Heavier and bulkier than down for equivalent warmth. For three-season backpacking in the Sierra, Rockies, or Northeast: down wins. For PNW or coastal hiking with persistent moisture: synthetic or treated down (850+ fill hydrophobic treated) closes the gap.

Variable 3: Shape — mummy vs semi-rec vs quilt

Mummy bag: tapered foot box and fitted hood minimize dead air space, maximizing warmth per ounce. Best for cold conditions (below 30°F). Semi-rectangular: more room to move, slightly heavier, better for warm sleepers at moderate temperatures (35–50°F). Quilt: lightest option, works well for warm sleepers who don't move much — attaches to sleeping pad to prevent cold spots. Cold sleepers and restless sleepers frequently wake cold with quilts; mummy bags are more forgiving of movement.

What fill power rating do you actually need?

800-fill power is the sweet spot for three-season backpacking — better warmth-to-weight than 600-fill, no meaningful performance difference versus 900-fill for most users (900-fill saves approximately 1.5 oz on a 20°F bag). Below 600-fill: adequate for car camping where weight doesn't matter. Above 850-fill: worth the premium for ultralight backpackers counting every gram. Western Mountaineering ($500+) and Feathered Friends ($400+) use 850–950 fill power in their premium bags — the weight savings versus 800-fill are real but the price premium is significant.

How long does a down sleeping bag last?

With proper care — stored uncompressed in a cotton storage sack, washed every 20–30 nights of use with technical down wash (Nikwax Down Wash), and tumble-dried with tennis balls to restore loft — a quality down sleeping bag maintains 90%+ of original loft for 10–15 years. The primary degradation mechanism is compression set (permanent loft loss from extended storage compressed) and contamination from body oils (reduces hydrophobicity). Never store a down bag compressed in its stuff sack for more than 2 weeks.