How to Choose Sleeping Bag

1. RECTANGULAR

Rectangular bags are the most traditional sleeping bag — roomy, with plenty of space to stretch or roll over, rectangular bags lean more toward comfort than warmth.

Because rectangular bags are larger than other types of bags, they don’t retain as much heat. That makes them a common choice for warm-weather camping. As an added benefit, if you get too hot while sleeping or if the weather is unexpectedly muggy, you can unzip a rectangular sleeping bag and use it as a comforter instead.

While rectangular sleeping bags don’t retain as much warmth as semi-rectangular or mummy-style bags, they provide plenty of space to move, which is helpful for restless sleepers or campers who might feel a little claustrophobic in a more form-fitting bag.

2. SEMI-RECTANGULAR

Structurally, semi-rectangular sleeping bags are similar to mummy-shaped bags. However, unlike the mummy, semi-rectangular sleeping bags don’t completely conform to the shape of your body.

Also called a barrel or modified mummy shape, semi-rectangular bags can come in a variety of shapes. Most models are generally more slender than rectangular bags, with a rounded top and a slight tapering at the bottom.

 

Semi-rectangular bags aim to find the perfect balance between warmth and roominess, so you don’t have to completely sacrifice wiggle room for the sake of heat retention. That makes them well-suited for cool-weather camping when conditions are chilly, but not frigid.

3. MUMMY

As their name suggests, mummy sleeping bags are meant to fit snugly.

Hooded and shaped to follow the contours of a human body, mummy bags are all about warmth. Their design doesn’t account for roominess — if you roll over, you’re likely to roll with your bag instead of inside it. However, the fitted shape provides maximum heat retention, keeping you warm in bitterly cold conditions.

The science behind it is straightforward — to maximize heat, mummy bags minimize the amount of air space around your body in the bag. This low air space means your body will quickly heat the air inside the bag, and less air gets pushed out of the bag when you shift or move while you’re asleep.

 

Mummy bags are also typically lighter than many other sleeping bag shapes, making them a popular choice for backpackers.

4. DOUBLE

Double sleeping bags are for couples who want to sleep together while camping. Roomy enough to comfortably fit two adults, double bags are typically wider versions of a rectangular bag, but it’s possible to find double versions of barrel and mummy bags as well.

 

With the right bags, you can make a DIY double sleeping bag. Some single-sized rectangular bags have special zippers that can attach to another bag — if you and your partner purchase the same brand and model, you may be able to create a makeshift double-sized sleeping bag.