Sleeping Bags Under 1 kg

How much warmth you really get under 1 kg

The backbone of this class is 800+ fill-power down. Those bags typically weigh 700–1,000 g and cover comfort ratings of roughly −5 °C to +5 °C (23–41 °F) — classic three-season territory. The median weight in this list is around 720 g, and right at the kilo boundary you will even find models with limit ratings near −9 °C (15 °F).

Below about 500 g the selection turns firmly summery. The lightest bags start around 240 g, and their comfort ratings sit well above +5 °C (41 °F): hut trips, warm valley nights, or a thin bag paired with a warm baselayer — not frosty mornings.

Limit is not comfort — and synthetic only fits under 1 kg in summer

Makers like to advertise the limit rating, because the number looks colder. Under ISO 23537 the comfort figure typically sits 5–6 °C (9–11 °F) higher, so a bag sold as a "0 °C bag" often only sleeps warm from about +5 °C (41 °F) up. Check the comfort value on the product page before you buy.

Synthetic fill makes the kilo cut only at summer and mild shoulder-season temperatures: for the same warmth it needs roughly one and a half times the fill weight of good down. The synthetic models here carry limit ratings of about −1 °C to +7 °C (30–45 °F). If you expect persistent damp and still want to stay under 1 kg, a light down bag in a waterproof stuff sack is the better trade.