Loft
Loft is the thickness of a sleeping bag's insulation when the fill is fully puffed up. The fill traps warm air in that space, so a bag with more loft can hold more warm air, all else being equal.
Where you'll see it
It comes up on sleeping bag product pages and in buying guides, usually alongside the fill type. Loft depends on the fill, the way the bag is built and how it was packed away, so a bag can look flatter after storage. Shake it out and let it fluff before you judge it.
What to check
- Whether the maker describes the loft, or the fill that creates it.
- The fill type, since down and synthetic fill behave differently when damp.
- The packed size, to check it suits your car or rucksack.
- The maker's advice on storage, since squashed storage can flatten the fill.
Related terms
- Down fill: one common fill that traps warm air.
- Synthetic fill: the other common fill, which copes better when damp.
- Comfort rating: the figure to compare bags by, since loft alone does not show warmth.
Read more: sleeping bag temperature ratings explained.