How to Choose a Sleeping Bag
Picking out a sleeping bag can be tricky. There are a plethora of different options, and usually the best bag for you depends entirely on how you plan to use it and how cold/warm you tend to sleep. With this guide, I hope to break down the important things to look for in a sleeping bag and help you narrow down what bag you need for your next trip!
Temperature Ratings
Likely the first thing that you are going to notice whenever you start looking at sleeping bags is the number attached (REI Men’s Trailbreak 20 or Marmot Trestles Elite 20 - Women’s). This number signifies the temperature at which a particular person would be comfortable within that bag. As you might have already been thinking, what defines a comfortable sleep and for whom? In the world of sleeping bags, it is assumed that the average man sleeps warmer than the average woman, and with that, the typical men’s bag will have less insulation than a women’s bag rated to the same temperature. The number attached to a men’s sleeping bag is the lower limit temperature at which an average man would feel comfortable, and the number attached to a women’s bag is the lower limit at which an average woman would feel comfortable.
In order to find what temp rating you need in your sleeping bag, you first need to consider what the low temperatures will be when you plan on camping. Obviously, your needs in a sleeping bag will be different if you plan on winter camping in Minnesota vs spring camping in coastal California. As a rule of thumb, consider the lowest temperature that you think that you will experience while you are camping then subtract another 5-10F (3-6C) from that to get the temperature rating that you should target in your next bag. It is always good to give yourself a little buffer of extra warmth just in case things get colder than expected. If you end up too warm, you can simply sleep on top of your bag. Here is an example of a calculation that I made whenever I bought my first sleeping bag. I planned on camping during winter in west Texas where I know that the lows can reach around 25F. Thus, the temperature rating that I targeted was 15F (25F-10F). For a cold sleeper, you may want to even add another 5F to that buffer mentioned above (subtract 10F-15F from the lowest temps you plan on encountering).
Fill Types
There are two main types of sleeping bag fill: down and synthetic. The right option for you depends on a variety of factors.
Down sleeping bags are known for packing extreme warmth in a lightweight package. They are also very compressible which makes them a great option for backpacking where space and weight are at a premium. Unfortunately, these positive features come at a higher price than their synthetic counterparts. As another downside, down loses its loft (and thus its insulating properties) whenever it gets wet. While many modern bags coat the interior down in a water-resistant coating to alleviate moisture buildup, they still do not perform well when fully wet. With these considerations, you should choose a down bag if you need something lightweight, packable for its warmth, but are planning on trips where you can make sure that the bag stays dry.
Synthetic sleeping bags offer a lot of bang for your buck. While they are heavier and not as packable as their down counterparts, you can get a very warm bag for a very reasonable price. Another upside is that synthetic sleeping bags keep their warmth even while wet. This allows them to be a little more versatile and care-free than down. If stored properly (out of their stuff sack, hung up), they can also have excellent longevity on par with down fill bags. If you are able to deal with their slightly heavier and less space-efficient properties, you will be able to secure a much warmer bag at a lower cost than a down equivalent.
Bag Shape
Bag shape and size can also play a big role in how warm your bag will keep you. To maximize warmth, you want a sleeping bag that forms just close enough to your body that there are no large air pockets between you and the bag. If these air pockets exist, just know that your sleeping bag will sleep a little bit cooler than its rating suggests. With that extra room though, you may gain slightly more comfort if you are an active or side sleeper (like myself). There are several different shapes and sizes of bags that you will often see: regular/long, mummy/rectangular/spoon-shaped, and men/women.
Regular vs. Long
Although the exact specifications vary, a long bag is typically around six inches longer (and a couple inches wider) than a regular bag. This follows for both men’s and women’s bags. If you are taller, you may want to consider a long sleeping bag.
Mummy vs. Rectangular vs. Spoon-shaped
If you are looking to buy a newer bag from an outdoor gear shop, you are most likely familiar with a mummy bag. The distinctive wide shoulder design with a taper near the footwell of the bag lends it the mummy name. These bags attempt to form to the natural curves of your body a bit better than a classic rectangular design. With that form fit, your body does not need to heat as much air within the bag, and thus, you will maximize warmth. The main drawback to a mummy bag is that this snug fit can decrease comfort and make it hard to move around if you are an active sleeper. The benefits of the classic rectangular shaped bag are that you can likely find one for a very inexpensive price. With that, you may not receive the most high quality materials, warmth, or weight savings, but these bags will do the job if you do not need to maximize those qualities. I would reserve the classic rectangular shape for car-camping or RV-ing scenarios, but they can do perfectly well in those situations. The newest member of this list is the spoon-shaped design (e.g. the NEMO Riff 15). The wider shoulders and wider footwell of this design make it ideal for side sleepers who may need to move around a bit while they are sleeping. Although the design does allow for larger air pockets to form between your body and the bag (which can lead to cold spots), it could possibly be more comfortable. That balance between warmth and comfort comes down to personal preference.
Men’s vs. Women’s
The men vs. women cut of bags is the most straightforward difference. We talked earlier about how a women’s bag contains more insulation than a men’s bag for the same rating. The shape of a women’s bag is also slightly different in that it is cut a bit wider around the hips. Consider this when looking at sleeping bags, as you may be better suited for a men’s or women’s bag depending on your body shape.
Weight and Packability
Weight and packability are the two other main considerations that you need to make when choosing a sleeping. Depending on your circumstances, you will need to prioritize these two things differently.
If you plan on going on an extended backpacking trip, you will likely need a bag that is both light and very packable. This would probably be best served by a down mummy bag. With that said, a synthetic bag could do the trick as well. It would be slightly heavier and may not pack down quite as tight, but it would do better in wet weather.
If you are strictly going to use this bag for car camping, both weight and packability don’t need to be considered that much. In this scenario, possibly a rectangular bag with a super comfortable interior liner may suit you best.
As you can see, picking out a sleeping bag can be a bit complicated. It is all about picking the right bag for your needs. Hopefully with the guidance above, you can hone in on what type of bag will suit your needs best.
