A sleeping bag rated to -5°C does not mean you will be comfortable at -5°C. Here is how ratings work and what you need for Australian conditions.
The Comfort vs Limit Rating
Modern sleeping bags carry two ratings under EN 13537 or ISO 23537:
Comfort rating: Temperature at which a "standard woman" sleeps comfortably in a relaxed position.
Lower limit: Temperature at which a "standard man" can sleep for eight hours without waking.
Most manufacturers advertise the lower limit. Most buyers assume it is the comfort rating. Practical rule: add 5–8°C to the advertised rating to find your actual comfort zone.
Australian Conditions Guide
Coastal summer (15–25°C nights): Bag rated 5°C comfort or higher.
Victorian high country autumn (5–15°C nights): Rated -5°C comfort.
Alpine winter (−5°C to −15°C nights): Rated -15°C comfort minimum.
Tropical dry season (20–28°C nights): A thin liner or a bag used as a quilt.
Down vs Synthetic Fill
Down: Better warmth-to-weight. Loses insulation when wet. Right choice for alpine and dry conditions where you carry weight over distance.
Synthetic: Heavier but insulates when wet. Better for coastal or unpredictable camping.
Ground Insulation Matters Too
Cold comes from the ground faster than from the air. Your sleeping pad R-value should be at least 2 for summer, 4+ for shoulder seasons, 6+ for alpine.
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