Mummy sleeping bags are perhaps the most popular bags among outdoorsmen for many reasons. They’re a must-have for when the weather is cold, or when you find yourself camping at high altitudes. Mummy bags tend to be their widest at the shoulders and then taper down to a narrower head and footbox. They’re also lightweight, due to the fact that they use less material than other bag types, and the lower amount of internal air space provides more warmth. Their narrow design can make sleeping a bit too snug or uncomfortable for some, though, and they tend to be the most expensive bag type, so you’ll need to decide for yourself if a mummy bag is right for you.
While rectangular bags tend to offer more sleeping room, this also creates a lot more air space that your body needs to heat up, making them a little unfit for colder weather. Furthermore, rectangular bags tend to be heavier and bulkier, making them a cumbersome for some backpackers, but they can be fully unzipped to create a comforter. Unlike mummy bags, rectangular ones almost never come with a hood. In general, they’re best for people who move a lot while they sleep or those who don’t want to spend a lot.
Now, you might also be able to find hybrid bags that fall somewhere in between the two listed above. These bags are wider at both the shoulders and hips, but also taper to the head and footbox. They’re heavier, but roomier than mummy bags, and also lighter than rectangular bags. Hybrid bags are great for those who find mummy bags to be too restrictive, or rectangular bags too cold.
Many campers and hikers tend to look at either price or feature when they look at a piece of outdoor gear, especially sleeping bags. The tips outlined above will help blur the lines of consideration the next time you’re turning your head from a rectangle bag to a mummy bag, and back again.