How to Choose a Sleeping Bag: Temperature Ratings, Fill Types, and What Actually Matters
The sleeping bag is the most consequential piece of camping gear for a specific, simple reason: if you are cold at night, the camping trip fails. Cold disrupts sleep, produces miserable mornings, and creates the “I’ll never camp again” conclusion that a warmer bag would have prevented. The sleeping bag decision is worth getting right, and the specifications that determine whether a bag is right for your use are specific and learnable.
Temperature Ratings: More Conservative Than They Appear
Sleeping bag temperature ratings use the EN/ISO 23537 standardized testing protocol that measures the temperature at which a “standard” person can sleep comfortably. The important qualifier: the standard person is a male weighing 25 years old — women typically sleep colder than the male standard, and most people sleep colder than the standard at the upper limit of their comfort. A bag rated to 30°F will keep most people alive at 30°F but will not provide comfortable sleep at that temperature for the majority of users. Buy a bag rated 15 to 20 degrees below the coldest temperature you expect to encounter, not the exact coldest temperature.
Down vs. Synthetic Fill
Down sleeping bags compress smaller, weigh less, and last longer than synthetic bags at equivalent warmth levels — advantages that matter most in backpacking where pack size and weight are critical. The traditional disadvantage of down — losing insulating value when wet — has been substantially addressed by hydrophobic down treatments (850+ fill power treated down) that maintain much of their loft when damp. Synthetic fill bags insulate when fully wet (an advantage in reliably wet environments), dry faster, and cost less than comparable down bags. For car camping where weight and pack size are irrelevant, a synthetic bag at lower cost is a rational choice. For backpacking, treated down provides the warmth-to-weight ratio that synthetic bags cannot match.
