How do I choose a sleeping bag for backpacking?
Temperature Rating
Sleeping bag temperature ratings indicate the lowest temperature at which an average sleeper stays comfortable. Ratings vary by standard: EN 13537 (Europe) and ISO 23537 (international) are common, but U.S. brands often use their own. As a rule, choose a bag rated 10–15°F (5–8°C) lower than the coldest temperature you anticipate for comfort, especially if you sleep cold.
Consider the season and location. Summer backpacking might need a 30–40°F bag, while three-season use calls for 15–30°F, and winter requires 0°F or lower. Women typically sleep colder than men, so many brands offer women-specific bags with extra insulation.
- Check the comfort rating, not just the lower limit.
- Add a sleeping pad with adequate R-value to insulate from the ground.
- Use a liner to boost warmth by 5–15°F.
Insulation Type
Down insulation offers the best warmth-to-weight ratio and packs small, but loses loft when wet and costs more. Synthetic insulation retains warmth when damp, dries faster, and is cheaper, but is bulkier and heavier for the same warmth. For wet climates, synthetic is often safer; for dry, cold conditions, down is ideal.
Down is rated by fill power (e.g., 600, 800, 900+). Higher fill power means more loft per ounce, so a 800-fill bag is lighter and more compressible than a 600-fill bag of the same rating. Synthetic bags use continuous filament or short-staple fibers; quality varies, so read reviews.
- Down: lighter, more compressible, less durable in wet conditions.
- Synthetic: heavier, bulkier, but performs better when wet.
- Treat down with a water-repellent finish for added moisture resistance.
Fit and Features
A bag that's too large has dead air space that your body must heat, reducing efficiency. Too small compresses insulation and feels restrictive. Mummy bags are most efficient for backpacking; rectangular bags are roomier but heavier. Check shoulder and hip girth, and consider a women's-specific cut if you have a narrower shoulder and wider hip.
Look for a draft collar, hood, and zipper baffle to prevent heat loss. A two-way zipper allows ventilation. Also consider pack size—down bags compress smaller. If you're tall or broad, many brands offer long and wide versions.
- Try the bag in person if possible; lie in it and simulate sleeping.
- Check the zipper side: left or right zip affects compatibility with another bag.
- Storage: keep it loose in a cotton sack, not compressed.
Common mistakes
- Assuming the temperature rating is a comfort rating—it's often the lower limit for an average man.
- Buying a bag that's too big, which creates cold spots and reduces efficiency.
- Neglecting the sleeping pad's R-value; no bag will keep you warm if the ground saps your heat.
