- Rectangular
The rectangular sleeping bag is probably the most common and are popular for light use. They are not suitable for backpacking because they provide the least amount of warmth and the most amount of weight. As the name implies, they are rectangle-shaped. While this makes them comfortable and roomy, the wide opening near the top is a major source of heat loss. Unlike a mummy bag it does not have a hood that can be drawn around the head to retain heat.
- Mummy Bag
The mummy bag is shaped like a sarcophagus. It is narrow at the feet (but tall there to allow just enough room for the feet), tapers at the waist, widens again at the shoulders, and then tapers down near the head. The top is very much like the hood of a winter coat, complete with drawstrings to close up the gap and keep heat in. Because they conform so well to the human shape, there is very little wasted space inside. This is good because your body has to heat all that space, and because the extra insulation and material thusly removed does not have to be carried (meaning it's lighter).
- Barrel Bag
The barrel bag is a modified mummy bag. It is roomier than the mummy bag and provides almost the same warmth at the cost of additional weight.
