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How to Choose a Sleeping Bag: Shapes and Sizes

Choosing the right shape and size sleeping bag is an important consideration when purchasing a sleeping bag. Knowing the differences will help you determine the right sleeping bag for your needs.

How to Choose a Sleeping Bag: Shapes and Sizes

Whether you are going out for days in the backcountry or spending a weekend car camping, the shape and size of your sleeping bag is a big consideration for getting a comfortable, restful night’s sleep. This how-to considers different shapes and sizes of sleeping bags to help you determine what type is best for you needs.


The first type of sleeping bag you might try is the rectangular-style bag. Most of us are familiar with this style, and it’s what we think of first when we think of sleeping bags; it is the roll up, tie down type of bag. This style is great for family camping, car camping or someone who wants a lot of room to spread out and be really comfortable in a sleeping bag. These are great bags because they can also be spread open and used as a blanket. They often feature the ability to zip together with other sleeping bags to make double sleeping bags or a bigger blanket. The downside to rectangular bags is they tend to be heavier because there is a lot of material in their construction. They are roomy, but they are not as compressible or packable. They do typically feature a more budget-friendly price tag than other, more technical bags, though.


The second style you might consider is the mummy-shaped sleeping bag. A lot of backpackers and lightweight camping enthusiasts are going to be familiar with this type of bag. It often features a hood. It is broad around the shoulders and then dramatically tapers in at the feet. The idea behind a mummy bag is the reduction of extra fabric and fill that would be in a rectangular bag, but might be somewhat extraneous. The mummy bag really hugs your body, which makes it more thermo-efficient. The less “dead air” and the less space your body has to heat in a mummy bag compared to a rectangular bag, the warmer you are going to be (and the warmer is going to get) once you’re tucked into the bag.


A lot of mummy-style bags will have a three-quarter length zipper or a half zipper to be a little more thermo-efficient. Some have a zipper that goes almost to the bottom (and some have no zipper at all), so there is a lot of variety in mummy-style bag construction Over all, they are a lot lighter weight than traditional rectangular bags across the spectrum. They pack down to be smaller in most cases, and are simply a great option for someone who wants to go lightweight, but also wants a very warm bag.


The fit of a mummy bag should be rather snug, though it should not be so snug that your feet are hitting the bottom and your head is stretching the top of the hood. You don’t want to compress any of the bag’s insulation in those areas, as compressed insulation will not be as warm. Ideally, you want to have a little bit of room to move, but, likewise, if the bag is too long for you or much too wide, your body isn’t going to be able to heat all that excess space as efficiently as that in a well-fitted bag.


Somewhere in between the rectangular-style and the mummy-style sleeping bags are a shape that’s semi-rectangular. These bags taper in a little bit at the feet for more thermo-efficiency, but do not taper as dramatically as a mummy bag. They also often do not have a hood. This shape is a bit versatile, though, in that you can form a sort of hood if you need to and cinch the bag down near the top; this is not ideal, though. The foot box does taper in, but the zipper typically runs all the way down the bag and all the way the way around the footbox. Unlike most mummy bags, you can use this style as more of a blanket if you are traveling, like if you are staying in hostels during a foreign tour, though you can also take it long distance outdoor backpacking.


Another sleeping bag style you might encounter is a sleeping bag/sleeping pad combination. With a traditional sleeping bag of any shape, you are sleeping right on top of your sleeping pad with your weight compressing the insulation in the underside of your bag. In a sleeping bag/pad combination you are able to either slide a sleeping pad right into a sleeve on the bag or connect it some other way. These bag/pad combinations come in a variety of shapes and sizes like the bags we’ve already discussed. As we already covered, once compressed, the fill of a sleeping bag loses most of its insulating properties. Thus, the idea behind a bag/pad combination is that the pad gets connected directly to the bag to provide not only a very secure foundation that allows you to roll or twist during the night without ever rolling off of your pad, but protection against exposing your body to the cold ground as you sleep. Some bags that are designed to work in tandem with pads do not have any insulation in the underside of the bag. This may seem like a bad idea, but since you have that sleeping pad connected to the bag providing insulation and warmth that is not going to move during the night, the insulation on the bottom of the bag is unnecessary.


In addition to shapes and sizes to consider, sleeping bags often have gender-specific construction. Women’s specific bags have a shorter, narrower size, and they often feature more insulation in key areas that women tend to lose heat faster than men. There is typically a little bit more insulation in the feet and sometimes there is more insulation across the middle region, across the chest and abdomen areas. These are not major differences, so if you are a taller woman and feel you need the extra space and length that a men’s bag might offer, don’t hesitate to choose the men’s bag.


Before we conclude this how-to, there are a few miscellaneous points to consider when thinking about the right sleeping bag shape and size for you. First, think about whether you’ll want to zip two bags together to create a double bag. Rectangular bags can easily zip together, but zipping two mummy bags together may require more creativity. You will need two mummy bags with the same type of zipper and opposite side zippers. So, one bag will need to have a right hand zipper (zippers on the right side of the bag) and the other will need to have a left side zipper so you are able to zip the top and bottom portions together to create one bag. Some sleeping bag brands offer double-wide bags with room for two people inside and either one zipper or zippers on both sides. There are some extra wide sleeping bags for one person that are ideal if you may have a wider girth measurement or you just want to sprawl out and have a little bit more room in your bag.


All in all, there are many considerations when finding the correct size for your sleeping bag. Given all the different shapes available (rectangular, mummy, semi-rectangular) and the different options (hooded, non-hooded, sleeping pad sleeve, sleeping pad straps and zipper types), there are a lot of decisions to make when choosing a sleeping bag. Hopefully this guide has assisted you with the information needed to make a great choice.