7 Best Down Sleeping Bags (2026 Review Guide)

Fill power measures loft quality (how much space one ounce of down occupies), while down weight measures total insulation quantity – you need both numbers to accurately predict warmth. A bag rated 900 fill power but using only 8 oz of down will sleep colder than an 800 fill power bag using 14 oz. Manufacturers often advertise fill power prominently because it sounds impressive, but down weight is the more honest indicator of a bag's thermal performance.

At 900+ fill power, you're primarily paying for weight and pack size reduction, not meaningfully better warmth at equal down weights. If you're backpacking and every ounce matters, the premium is justified – a 900fp bag can hit the same temperature rating at roughly 20-25% less weight than a 650fp equivalent. For car camping or occasional use, a quality 650-750fp bag delivers the same warmth at significantly lower cost.

Mummy bags retain heat more efficiently because less internal air volume means your body warms the space faster and dead air loss through the shell is minimized – critical when temperatures drop below 20°F. Semi-rectangular bags trade thermal efficiency for comfort and freedom of movement, making them better suited for shoulder-season camping above freezing where claustrophobia outweighs heat retention. If your target conditions are consistently below 25°F, the mummy cut's thermal advantage is measurable, not just theoretical.

Most buyers treat the stated temperature rating as a comfort threshold, when EN/ISO ratings actually define the lower limit – the temperature at which an average male sleeper survives without hypothermia risk, not sleeps comfortably. The EN standard separately publishes a 'comfort rating,' which typically runs 10-15°F warmer than the lower limit figure many brands display. Always check whether a bag lists its comfort rating or lower limit, and if only one number is shown, assume it's the survival limit and plan accordingly.

Yes – most standard mummy bags are cut for a 6-foot, average-build body, so shoulder girth and hip girth are as important as length when selecting a bag. Check the manufacturer's shoulder circumference and hip circumference specs, not just the length rating; a broad-shouldered sleeper compressing a bag that's too narrow loses loft and warmth at the contact points. Many brands offer 'wide' or 'regular' width variants in the same temperature rating, and some offer women's-specific cuts with a narrower shoulder and fuller hip profile.

Wash in a front-loading machine on a gentle cycle with a down-specific soap – no agitator machines, which stress the baffles and can tear interior stitching. Dry on low heat with two or three clean tennis balls to break up clumping, and expect two to three full drying cycles to completely eliminate moisture trapped in down clusters. For storage, keep the bag loosely stuffed or hung in a large mesh or cotton sack, never compressed in its stuff sack long-term, as sustained compression permanently reduces loft and warmth over months.