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How to Choose a Sleeping Bag: Shapes and Sizes

Sleeping bags, like people, come in all shapes and sizes. The following guide explores the various shapes and sizes so you can find the right one for you and your needs.

How to Choose a Sleeping Bag: Shapes and Sizes


Rectangular sleeping bag, Marmot Yurt 35 Degree
Marmot Yurt 35 Degree

This familiar sleeping bag style is often associated with fond memories of family camping trips and sleep away camp. The iconic shape is comfortable and versatile, and is celebrated for the following reasons:

  • The ample cut offers plenty of room to spread out and move around inside

  • They can be opened up fully to be used as a large blanket

  • Many feature compatible zippers that allow two bags to zip together to create a double wide sleeping bag or extra-large blanket

  • Often, rectangular bags sport a more budget-friendly price tag

Due to the materials that are often used, they are likely heavier and less compressible than some other styles of sleeping bags.


Mummy sleeping bag, Big Agnes Spike Lake 15 Degree
Big Agnes Spike Lake 15 Degree

Shaped to mimic their namesake, mummy-cut sleeping bags employ a tapered profile to cut down on bulk and weight. These bags are a popular choice for backpackers and folks looking to reduce weight for several reasons:

  • The body-hugging fit eliminates excess and unused materials to increases thermal efficiency

  • An attached hood provides extra warmth in cold temperatures

  • They can pack down small to save space  

When fitting a mummy sleeping bag, look for one that is snug, but not to the point where your head or feet are stretching either end. Air is necessary for efficient insulation, so when compressed, the fill loses some of its ability to keep you warm.

Semi Rectangular

Semi-Rectangular sleeping bag, Sea to Summit Trek
Sea to Summit Trek

Somewhere in between the two styles, is a shape called “semi-rectangular”. These employ the benefits of rectangular and mummy styles for the best of both worlds:

  • Slight taper at the feet for increased thermal efficiency without feeling constricting

  • Can often open unzip completely to create a blanket

  • Does not always contain a hood

These shapes are a versatile hybrid that can be used in a wide variety of settings.


A style quickly gaining popularity in the world of weight conscious campers is the backless design. When lying in a sleeping bag, your body compresses all the fill on the bottom, which therefore loses most of its insulating properties.

By replacing that fill with a place to attach a sleeping pad, you essentially eliminate unnecessary materials (and therefore weight and space), while creating a secure and insulated surface to lie upon.

Women’s Specific Sleeping Bags

Within each of the categories of sleeping bags, many manufacturers create a women’s specific model with a few minor differences:

  • A shorter and narrower cut for more petite users- if you don’t need the extra space, why carry it?

  • Additional insulation in key areas where women tend to lose heat faster, such as foot and torso regions

Note that since these variations are fairly minor, taller women may prefer the additional room found in the unisex models.

As with all gear, there are many considerations at hand when selecting a sleeping bag. The variety of sizes and shapes help you find the best sleeping bag option for your needs.