Sometimes the right fit does not always match your gender, as proven by this comfy camper who found his perfect bag in the Women’s Mira. Photo: Forest Woodward

OK, so now you understand EN Temperature Ratings and have selected a sleeping bag that will keep you warm on your adventures, plus you’ve weighed the pros and cons of down versus synthetic insulation and made your decision. What’s next? Choosing the correct fit. Sleeping bags aren’t like a pair of jeans, meaning that you shouldn’t rock them extra tight just because you consider yourself a fashionable hipster, or choose a baggy fit because you’re in to that whole 90’s skater look. Why? Because a sleeping bag that fits too tight or too loose means you’re losing warmth. So how do you achieve the right fit? Here are some tips to make sure you’re choosing the best fitting sleeping bag.

The Length

Sleeping bags are sized by their length, and though this may seem obvious, the correct length for your bag should correlate directly with your height. For example, if you’re 6 feet tall, you want to try sleeping in a 6 foot bag. But don’t think that a 6-foot sleeping bag should fit like a glove. A 6 foot sleeping bag will actually measure roughly 6-foot 8-inches long, giving a 6-foot tall person the extra room needed for a correct fit. Why the extra room? When we lay flat, our spines decompress, our feet fall forward and our bodies spread out. As a result, sleeping bag designers compensate for this by adding a few extra inches to the length.

But what if you are a 5’ 6” male and the smallest men’s bag available is a Regular—a 6 ft. bag—that actually measures 6ft. 8in. from the hood to the toe box? This is the perfect moment to swallow your pride and consider buying a women’s regular. A Therm-a-Rest women’s regular is a 5’6” bag that will measure roughly 6’2” on the inside, making it a great size for a 5’6” man.

The Shape

The shape of your sleeping bag should reflect the style of camping you’re planning on doing. There are four basic shapes of bags: Mummy, Rectangular, Semi-Rectangular, and Double-Wide. We’ll break it down to help you decide which shape best fits your style.

1. Mummy—shaped like a sarcophagus, the mummy bag has a snug fit that tapers toward the feet, making it the warmest option. This shape allows the least amount of air between you and the insulating wall of the bag, meaning there is less air to heat. And because of its efficient shape, it’s also lightweight and packs easily, making it the ideal choice for backpacking or technical adventures that require packability but also a high degree of warmth. The downside? Room. A mummy bag can be restrictive, making it uncomfortable for tossing and turning sleepers.

2. Rectangular—as the name implies, this is a non-tapered design, which is less efficient at heating, but also less restrictive while sleeping. Warm weather car campers often opt for a rectangular shaped sleeping bag due to the freedom of movement they provide. If comfort, not warmth, is your main priority, consider this style of bag.

3. Semi-Rectangular—a hybrid between the mummy and rectangular shape, this is the go-between for fair-weather campers that require warmth, but also desire the extra room for added comfort. While not as warm as mummy bags that can withstand 3 to 4 season camping, a semi-rectangular bag can work for fair-weather trips, and also be efficient enough for shorter backpacking adventures. Check out our new Dorado for the perfect example of a semi-rectangular bag.

Therm-a-Rest Parsec Sleeping Bag


Finally, in conjunction with the shape and length you choose, a major factor to consider when fitting your bag is how much room or dead-space you have once you’re lying inside. A sleeping bag works by trapping and then heating the air between your body and wall of the bag. So the less air the better right? Wrong. A bag that fits too tight won’t work properly because you’ll be crushing the insulation (i.e. the down or synthetic fill) with your body size, therefore effectively eliminating the bag’s heat-trapping capabilities. Too much room, however, will result in inefficiency by creating too much air to heat, which will also weaken the bag’s ability to keep you warm.

So it’s a balance. Like length, roughly eight inches of space between you and the walls of your bag is a good place to start. This allows you enough room to wear a base layer to bed (which wicks moisture away from your body and keeps your body-oils from damaging the bag’s fill) while also allowing your bag to efficiently trap and heat the non-circulating air around your body.

We also realize that some campers are uncomfortable when a bag feels too tight, so to combat this feeling, we’ve added girth to our mummy bags between the hips and shoulders, giving sleepers the freedom to move and wear a jacket in extra cold conditions. The bottom line, however, is that room is a personal preference, but the right balance will increase your bag’s performance.

Try It On!

Like a jacket, the best way to get the right fit is to try them on if you can. It’s important to realize that each brand of sleeping bag as well as model will fit differently. So finding the right sleeping bag is a matter of patience and exploration, but with this information, we hope you’ll be able to dial in the perfect fit.

<< Choosing the Right Sleeping Bag: Part 2—Down Vs. Synthetic

Choosing the Right Sleeping Bag: Part 4—Understanding the Underestimated Camp Quilt>>