Sleeping Bag for Women in Cold Weather: Ratings Explained

For cold-weather camping, buy a women’s bag by its ISO comfort rating and ignore the number in the name. Women’s bags are rated differently from men’s: Nemo states that its women’s temperature is the comfort rating (the warmer threshold at which an average woman sleeps comfortably) while the men’s number on the same bag is the limit rating. That is why a women’s 15 contains more insulation, weighs a few ounces more, and is genuinely warmer than a men’s 15. For nights forecast in the 20s, a women’s bag with an ISO comfort of 15 to 17F is the right tool; for nights in the teens or single digits you want a comfort rating near 0F, and at that point the pad under you matters as much as the bag. The three bags below all publish their comfort number, which is the first filter.

How women’s ratings actually work

The ISO 23537 test (formerly EN 13537) produces two numbers for every bag: comfort, the temperature at which a standard woman sleeps relaxed, and limit, the temperature at which a standard man sleeps curled up without shivering. Both numbers assume one base layer, a hat, and an insulated pad. Brands then choose which number to print on the women’s bag. Nemo’s explanation is the clearest: its Disco Women’s 15 has a comfort rating of 15.4F and a limit of 5F, while the Disco Men’s 15 has a limit of 13.5F and a comfort rating around 24F. Same name, roughly 9 degrees of difference, because the women’s version is rated on the harder test and filled to pass it.

So when you compare a women’s bag to a unisex one, compare comfort to comfort. A unisex bag labelled 15 with a comfort rating of 27F is not a 15-degree bag for a woman. A women’s bag labelled 15 with a comfort rating of 17F is.

Pick the number by the forecast, not the season

Take the coldest overnight low you expect and buy a comfort rating at or below it. Shoulder-season trips with lows in the high 20s are covered by the comfort 15 to 17F bags here. Lows in the teens want a comfort rating around 5F, which usually means a bag labelled 0. Below that you are in true winter bags, which are heavier, more expensive, and worth renting before you buy. Err warm: a bag that is 10 degrees too warm unzips, and a bag that is 10 degrees too cold ends the trip.

Women also, on average, run colder at night than the test assumes; Nemo puts the gap at 10 to 15 degrees of perceived warmth. If you know you sleep cold, treat the comfort rating as the limit and buy one step warmer.

The women’s cut: when it helps and when it hurts

A women’s bag is shorter (Regular typically fits to 5 ft 6 in, Long to 6 ft), narrower at the shoulder, wider at the hip, and carries extra fill in the foot box and over the torso. For a woman under 5 ft 6 in with average shoulders this removes dead air, which is the single biggest warmth gain available without adding fill. For a tall or broad-shouldered woman it does the opposite: Outside’s reporting quotes a 5 ft 9 in tester who found a women’s bag too tight at the shoulders and too short. If you are over 5 ft 8 in or measure more than about 48 in around the shoulders, buy the Long or a unisex bag with the same comfort rating and look at plus-size sleeping bags for girth numbers.

Down or synthetic for cold nights

Down (650 to 800 fill power in the bags here) is warmer per ounce and packs smaller, and treated down handles condensation inside a tent. Synthetic is heavier for the same comfort rating, about 4.5 lb against 3 lb at 15F, but it keeps insulating when soaked and costs half as much. For backpacking in cold, dry conditions, down. For car camping, wet climates, or a first winter bag, synthetic is the lower-risk purchase.

Bags that publish a comfort rating

Nemo Disco Women’s 15

The reference women’s cold-weather bag: 650-fill hydrophobic down, ISO comfort 17F and limit 4F, a spoon shape with room at the elbows and knees for side sleepers, and a draft collar. Regular fits to 5 ft 6 in and Long to 6 ft; Nemo also cuts Regular Wide and Long Wide sizes. Shoulder girth on the Regular is 60 in. Priced $269.95 to $349.95 at Nemo depending on size. Check price on Amazon

Nemo Riff Women’s 15

The same women’s rating logic and spoon shape with 800-fill down, which makes it lighter and smaller packed for the same warmth. Nemo lists it at $359.95 to $449.95. Buy this over the Disco if you carry it far; buy the Disco if you mostly drive to camp. Check price on Amazon

Marmot Trestles 15 Women’s

The synthetic value pick, with a tested comfort rating of 16.7F and limit of 3.6F, SpiraFil fill, 4 lb 8 oz in Regular (fits to 5 ft 6 in; a Long fits to 6 ft), and a full-length two-way zipper. Marmot has listed it as low as $139. It is heavy and bulky next to the Nemos and that is the whole trade. Check price on Amazon

The pad is half the system

Every rating above assumes an insulated pad. On cold ground the bag’s insulation under you is crushed flat and does almost nothing; the pad’s R-value is what stops the ground from taking your heat. For nights in the 20s use an R-value of 4 or higher, and for the teens, 5 or higher. A wide, warm pad also lets a wide bag work; the plus-size pad guide lists widths and R-values. Add a hat, dry base layers, and a hot drink before bed, and a women’s comfort-15 bag will handle most nights in the 20s. If you are consistently cold in the right bag on the right pad, the fix is usually a warmer pad before a warmer bag.