If you're going to carry a sleeping bag, then you might as well be carrying a lightweight sleeping bag. The core functionality of a sleeping bag is to keep you warm, but for every temperature rating there is a wide variety of sleeping bags available, with a wide variety of weights. Picking up an ultralight sleeping bag that is made with better materials and construction techniques might end up costing you more, but you get paid by many times over in the increased enjoyment most people get from having to carry less weight while backpacking.
Ultralight Sleeping BagFeatures to look for to make sure that you get an ultralight sleeping bag.
- Insulation Material - First and foremost, the weight of your sleeping bag will be determined by the material it is insulated with. The basic choice is down or synthetic, with down being the lighter of the two. Within the down category there is a whole range of qualities of down, with higher numbers for better quality down. 800+ fill down is quite good, for instance, but you can get the same amount of warmth with less down by using 900+ fill down.
- Shape - The rectangular sleeping bags that many people grow up using are hugely inefficient because there is a lot of wasted space inside the sleeping bag. It's a waste in that it's material not needed, and also in that your body heat gets used to heat that dead space within the sleeping bag. Which is why mummy sleeping bags are a better choice than rectangular.
Best Ultralight Sleeping BagsHere are a few of the better ultralight sleeping bags out there, across a range of temperature choices.
- Western Mountaineering HighLite Sleeping Bag - On the cooler side of things there is something like the HighLite, which has a temperature rating of 35 degrees. It uses 850+ fill down, which is very high quality, and weighs just 1 pound, or 453 grams, which is extremely ultralight. 35 degrees is fairly warm, so you likely don't want to use this sleeping bag outside of summer conditions, but for its temperature rating it is an extremely ultralight sleeping bag.
- Marmot Plasma +30 Sleeping Bag - At a slightly warmer temperature rating of 30 degrees there is the Plasma. This sleeping bag won the 2011 Backpacker Magazine Editor's Choice award. It uses 900+ fill down, which is extremely high quality, and weighs 1.37 pounds, or 637 grams, which is impressively lightweight. 30 degrees is warm enough for summer just about everywhere, and even some spring and fall conditions.
- Mont Bell U.L. Super Spiral Down #1 Sleeping Bag - If you're looking for something with a slightly lower temperature rating that can handle spring, summer or fall with ease, this is a good choice from Mont Bell. It's good down to 15 degrees, and uses 800+ fill down, along with a few features like a draft collar and Mont Bell's special biased construction technique to get there. It weighs a very respectable 2.25 pounds, which is 1.02 kilograms.