How to choose the right temperature rating sleeping bag for your adventure: A sleeping bag’s temperature rating identifies the lowest temperature at which a bag was designed to keep an average sleeper warm. Select a sleeping bag with a temperature rating that’s lower than the lowest temperature you expect to encounter. If you’re headed where you expect near-freezing temperatures, choose a 20°F bag instead of a 35°F bag. If temperatures are higher than expected, you can open up the bag to avoid overheating.
Synthetic insulation offers solid performance at an affordable price. Unlike down, it continues to insulate when wet, so it’s the bag of choice for damp climates.
The biggest factors in the weight of a sleeping bag are its insulation and its shape. More efficient insulation like advanced synthetics and high-fill-power downs, will deliver greater warmth for less weight than less efficient fills. Sleeping bags keep you warm by retaining heat emitted by your body, which can warm a small space up more efficiently than an expansive space. So, a bag with a sleek shape and a snug fit will be lighter than a similar bag that’s nice and roomy. Sleeping bags come in three basic shapes:
Rectangular – A lot of camping bags have a simple rectangular shape that maximizes roominess. Semi rectangular – Also known as a “modified mummy” or “barrel” shape, this designation covers a variety of shapes, all of which offer a compromise between warmth and roominess. Mummy – In order to boost warmth and reduce weight, this type of bag has a slim cut, along with a contoured hood you can cinch tight for greater warmth. Overall fit is snug—you typically roll over with your bag rather than inside of it.