The Complete Sleeping Bag Guide
A sleeping bag is the difference between a night of real rest and hours of shivering. Most hikers buy a bag rated too warm for their conditions — and on cold nights, they feel it.
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A sleeping bag is the difference between a night of real rest and hours of shivering. Most hikers buy a bag rated too warm for their conditions — and on cold nights, they feel it.
Temperature Ratings (ISO 23537 Standard)
Temperature Scale
Comfort Rating
Per ISO 23537 standard — temperature where an average woman sleeps comfortably, not curled up. This is the most relevant rating for purchase decisions. Women's bags are typically rated 5°C warmer to compensate for lower heat output.
Lower Limit Rating
Temperature where an average man can sleep curled up, without full comfort. Below this, real danger exists. Never plan a trip to the Limit rating — always use Comfort as your baseline.
Extreme Rating
Survival threshold only — hypothermia risk exists. This is a safety rating, NOT a comfort rating. Never plan any trip based on the Extreme rating. It is a survival floor, not a sleeping temperature.
Golden rule: choose a sleeping bag with a Comfort rating 5–10°C below the coldest temperature you expect. Nights in the field always feel colder than the forecast. For women: standard Comfort ratings are calculated for a male body — women's-specific bags compensate by rating 5°C warmer.
Fill Power
Fill power measures how many cubic inches one ounce of down lofts to. Higher = lighter and more efficient insulation. Premium down bags reach 950+ fill — among the highest commercially available.
550–600 Fill Power
Budget / Entry-Level
Basic down fill — heavier and packs larger. Suitable for occasional trips on a tight budget.
650–700 Fill Power
Best Value for Most Hikers
Best balance of price and performance. Light enough for multi-day trips. The most widely chosen range by tested hikers.
750–850 Fill Power
High Quality / Serious Hiking
Noticeably lighter and more packable. The difference shows up in your pack. Right choice for experienced hikers who don't compromise on weight.
900+ Fill Power
Premium / Ultralight
Best available. Premium down bags reach 950+ fill — among the highest commercially available. Premium price, but the weight savings are real on every trip.
Down vs. Synthetic Fill
🪶 Down Fill
Duck / Goose
✅ Pros
- +Lighter — best warmth-to-weight ratio available
- +Packs small — quality down bags weigh under 750g for 3-season use
- +Lasts decades with proper care and down wash
- +Softer, more comfortable loft feel
⚠️ Cons
- −Loses nearly all insulation when wet — dangerous in sustained rain
- −Dries slowly
- −Significantly more expensive — 2–3× the cost of comparable synthetic
- −Requires a specialized down-specific wash — not regular detergent
🧵 Synthetic Fill
Polyester / Synthetic
✅ Pros
- +Retains 80–90% insulation when wet — safer in rain
- +Dries fast
- +More affordable — accessible for all budgets
- +Allergy-friendly, machine washable with regular detergent
⚠️ Cons
- −Heavier — 1–1.5 kg for a 3-season bag vs. 450–700g for equivalent down
- −Packs to larger volume
- −Shorter lifespan — loses loft after 3–5 years of regular use
- −Less comfortable loft feel
Recommendation: In wet climates (Patagonia, Scandinavia, UK, Pacific Northwest) — synthetic is the clear winner. In dry regions (Israel Trail, Himalayas in dry season, desert) — down delivers significantly better performance at much lower weight.
Weight & Packed Size by Category
Summer Quilt
300–500g
2–5L packed
Ultralight 3-Season
450–700g
3–6L packed
Standard Down 3-Season
700g–1kg
5–9L packed
Budget Synthetic 3-Season
1–1.5kg
8–14L packed
Winter Bag (−10°C+)
1.2–1.8kg
10–15L packed