Bags come in several cuts and each shape is designed to appeal to a different type of camper.
A tapered cut through the legs and feet give mummy bags maximum thermal efficiency. A bag’s primary job is to contain the heat your body generates and when interior space is smaller, the bag is more efficient. Although most mummies have plenty of room through the shoulders and torso, restless sleepers and broader campers may be more comfortable in an alternative cut. Another benefit of mummy bags: because they use less materials and insulation, they’re lighter-weight and smaller to pack.
With no taper at all through the legs, rectangular bags are not as thermally efficient, and are best suited for backyard campouts and basement sleepovers.
A happy medium between mummy and rectangular shapes, semi-rectangular bags are a good choice for campers who can’t cope with the confinement of a mummy bag but need more warmth than a rectangular bag has to offer. They’re bulkier and heavier than mummies, but give you a bit more thrashing room.
BACKPACKER Tips: Sizing your sack
It’s a sleeping bag, not shrink-wrap. Here’s how to make sure your bag fits perfectly to ensure that you get the best night’s sleep.
1. Try before you buy. Crawl into as many bags as you can, wearing appropriate layers, to get an overall idea of the way each brand and type fits.
2. Integrate the sleeping pad. If a bag has a sleeping pad sleeve or straps, rig it that way in the store, because a pad will reduce the bag’s interior volume, ultimately affecting its fit.
3. Check the closures. Zip it up, down, and up again. If a zipper snags now, it will in the field. Cinch the hood and draft collar down. Check for a comfortable fit, a snug seal around your head, no scratchy Velcro rubbing against your cheek, and ease of exit.
4. Roll around. If you’re a cold sleeper or cold-weather camper, opt for a more snug fit. If you’re a thrasher or side sleeper, make sure you’re able to comfortably rotate your body.