Women’s bags are rated for comfort, men’s for survival

That’s the key difference.

Sleeping bag temperature ratings come from the EN/ISO standard, which gives three numbers: comfort, lower limit, and extreme. The comfort rating is for a cold-sleeping woman in a relaxed position. The lower limit is for a cold-sleeping man curled up. The extreme is “don’t die.”

Most men’s bags advertise the lower limit. Most women’s bags advertise the comfort rating. So a “20°F men’s bag” means you’ll survive but be shivering at 20°F. A “20°F women’s bag” means you’ll actually be warm and comfortable at 20°F.

How to choose: ignore the gender label. Look for the comfort rating. If you’re a cold sleeper (or a woman using a men’s bag), subtract 10–15°F from the advertised number. If you sleep hot, you can fudge the other way.

The takeaway is simple: buy a bag whose comfort rating matches the lowest