Sleeping bags come in a variety of styles and temperature ranges -- and prices, ranging from inexpensive flannel bags ("slumber bags") that are good for watching TV and sleepovers at home to high tech, sub-zero bags used by mountain climbers. You will probably want something in between for most family camping ventures. And you will probably want to resist the temptation to buy the warmest, most expensive sleeping bag you can find and afford. You will undoubtedly find it TOO warm during most "good" camping weather.
The flannel "slumber" bags with cute Mickey Mouse or Winnie The Pooh prints are fun for the kids at home, but are probably not warm enough or durable enough for camp use. Something with a tougher shell that is more resistant to dirt and easier to clean and warmer will be better for use in a tent or even an RV. That having been said, you could add a sleeping bag cover to your kid's favorite slumber bags if that makes them feel more at home.
Sleeping bags are usually given temperature ratings. How are those ratings derived? It probably isn't as scientific as you might think it should be. Manufacturers gives bags to employees or other "testers" and rate them based on the reports they get back. Whether a bag will keep YOU warm down to the rated temperature will depend on many factors other than the bag. First of all, are you a "Hot Sleeper" or a "Cold Sleeper"? If you kick the blankets off most of the time or your sleeping partner complains you make the bed too hot, you're probably a "Hot Sleeper". On the other hand, if you pile on the blankets, even in summer, you're most likely a "Cold Sleeper". "Hot Sleepers" will probably be comfortable down to the rated temperature, all other things being even . "Cold Sleepers" will need a bag with 10-15 degrees colder temperature rating to stay warm.
There are several other factors that significantly affect how warm you will feel in your sleeping bag. How easily you adjust to temperature changes is one. If you're slow to adjust, get a bag 5 or 10 degrees colder than the temperatures you expect. If you're not eating enough or drinking enough water during your outing, again adjust down 5 - 10 degrees. Can you sleep in a close-fitting (mummy style) bag? If not, get a rectangular bag 5-10 degrees colder. If you thrash around when you sleep you will expel warm air; get a bag 10-20 degrees colder. If you expect your bag to get damp or the weather is damp, go down 10-20 degrees to be comfortable. In windy conditions, you may need an extra 5-10 degrees in order to stay warm, depending on the density of the shell and the composition of the fill and your exposure to the breeze. If you're sleeping in a good tent or an RV wind will probably not be a significant factor.
Sleeping bags come in rectangular and form-fitting shapes. Rectangular bags can usually be unzipped and zipped together to form 2-person bags. I sometimes unzip a couple of old rectangular bags and use one under our sleeping bags and the second one on top like a comforter on especially cold outings. Form-fitting bags, often called "mummy bags" are narrow at the feet and wider at the shoulders. Form-fitting mummy bags are usually warmer for solo use because they have less air gap for your body to heat, but some people feel confined by them.
Be aware that form-fitting bags are gender specific. Bags designed for men are usually a littler longer and a lot wider at the shoulders and hips than those designed for women. A man will find sleeping in a bag designed for women a tight, almost claustrophobic fit. A woman sleeping in a bag designed for men will lose heat because the bag will be too loose on her. Bags may also come in different lengths for different height people. If the bag is too short the sleeper will have to bend their knees or part of their upper body will stick out. If the bag is too long, the sleeper will have excess air gap to keep warm. For best results and maximum comfort, choose a sleeping bag that fits you well. My personal preference is a bag that is a little long so that I have room to put my clothes at my feet so they won't be cold when I put them on in the morning. Extra tip: don't put wet or damp clothes in your sleeping bag!
Here are some general guidelines to use as a starting point for choosing a sleeping bag, then adjust as needed according to your personal and environmental needs:
Bag Type Temperature Rating (°F)
Summer Season +35° and higher
3-Season Bag +10° to +35°
Cold Weather -10° to +10°
Winter/Extreme -10° and lower
A good 3-season bag is probably the most versatile choice for most people. You can probably get by with a summer bag during warm summer months, but it won't keep you warm enough during early (Spring) or late (Fall) outings. You might need a Cold Weather or even Winter/Extreme sleeping bag for winter/snow camping, but you would end up unzipping it or getting completely out of it in the summer and maybe even during Spring and Fall outings. You can probably unzip a 3-season bag to stay cool enough to use it during warm summer outings.
Why not just buy the warmest bag possible? Sleeping in a Winter/Extreme bag in summer temperatures will be too warm. You may sweat and then get cold or unzip the bag and get cold. You need to match your sleeping bag to the climate. If I had to choose one bag to meet most of my needs, I would go with a 3-season bag. As the name implies, it will probably be comfortable in three seasons -- spring, summer, and fall, but inadequate for severe winter camping. On the other hand, if you're doing most of your camping in the sun belt in the summer, you'll probably want Summer Season bag; even a 3-season bag may be too warm then. Adding a liner and a cover and perhaps a wool blanket could turn a 3-season bag into a winter bag.
A military surplus "mummy bag" is often a good buy, especially if it comes with a sleeping bag cover. Just make sure you won't be claustrophobic in the close-fitting bag. Not all military surplus bags are the same so be sure to check the temperature rating or season specification. Some military bags, when used with the optional cover, are rated down to -20° F. So-called "mountain" bags are thought to be among the warmest military sleeping bags. Military sleeping bags are often really a "sleep system", consisting of a sleeping bag, a liner, and a cover. The cover is usually more or less waterproof for use without a tent. Depending on your requirements and the weather you may need all three components.
Storage can affect how well a bag will perform. If you leave your bag tightly rolled up in storage for extended periods of time it will loose "loft" and will no longer keep you warm down to the rated temperature. It is best to unpack sleeping bags and hang them up for storage. This allows any dampness remaining in the fabric to dry out and it prevents the fill from getting packed tight. If you hang your bags in a garage, shed, or basement where they may get dusty, cover them with a suit bag or a large trash bag. If the bag is damp, let it dry out for a few days before zipping it into a closed bag for extended storage. I once had a really nice10° mummy bag I ignorantly left rolled tight for many months in storage and it was completely ruined. The filling was so compacted in most places it was like there wasn't any at all. I found myself freezing in it when the temperature was in the high 30s! When it was new it easily kept me comfortable down to the rated +10° F.
Prices will vary depending on the quality, size, and temperature rating. Rugged, high tech, low temperature bags, like those used by mountain climbing expeditions, may run $900-$1000 each! You might pick up summer bags for kids at Walmart for under $20. Expect to pay $50-$100 for good 3-season adult bags. Those with tougher outer coverings will probably cost a little more but are also likely to last longer and may be a little more comfortable as temperatures drop.
Sleeping bag accessories include liners, covers, pads, and pillows. Liners are light weight, intended mostly to capture sweat and dead skin to keep it from contaminating the inside of your bag. Liners can be easily washed without worrying about compacting the fill since they are very much like sheets for sleeping bags. Covers are usually made of a sturdy, water-repellant or water-proof material, designed to keep sleeping bags dry when they are used outdoors in rain, fog, snow or heavy dew. Sleeping pads are essential for insulating YOU from the cold ground and for providing some padding between you and hard soil, rocks, sticks, etc. Pillows for use in sleeping bags are often inflatable so they don't take up much room when not in use. You can often stuff clothing in the sleeping bag bag for use as a makeshift pillow and not have to carry anything extra. Be sure to remove all the hard items (keys, cell phone, knife, wallet, etc) from your clothing if you chose this option. Liners, covers, and pads can all make you more comfortable in colder weather. Liners can sometimes be used by themselves on hot nights. Both liners and covers add extra insulation to keep you warmer on cold nights. Liners and covers function something like dressing in layers for cold weather, giving you more options to adjust to maintain comfort. Liners protect the inside of your sleeping bag from body oils. Covers protect the outside of your sleeping bag from dirt and weather.
Cleaning sleeping bags. First of all, minimize how often you need to clean them by using a sheet or a sleeping bag liner. When you must clean them, the best way is to send them to a dry cleaner. Some may have washing instructions on them, but personal experience with washing sleeping bags and fluffy parkas has not been good. One prevalent suggestion that is reported to be helpful is to dry the item in a tumble dryer with 2-3 clean tennis balls to dry to keep the "fluff" from clumping. If you have already washed an item and it is clumpy, try putting it back in the dryer with tennis balls for about 20 minutes. If that doesn't work, you will probably have to replace the item.
Used sleeping bags. Some people are adverse to using a sleeping bag that has been used by someone else, almost as bad as wearing somebody else's underwear! However, if it has been properly cleaned, it should be fine, and you can probably save a bundle of money. Make sure the filling still has plenty of "loft" and that there are no major rips, tears, or stains and that the zipper(s) work properly. Best to have sleeping bags dry cleaned, even if they are labeled machine washable. Machine washing is likely to cause the filling to bunch up.
Ultimately you should think more in terms a "sleep system" than a sleeping bag. A complete sleep system would include sleeping pad, sleeping bag, sleeping bag liner, and sleeping bag cover. Together they will provide you with the best comfort, convenience, and protection. Each has its own function to perform. The sleeping pad insulates you from cold, bumpy ground. The sleeping bag provides the primary insulation against cold. The sleeping bag liner adds a little more insulation and protects the sleeping bag from sweat etc. The sleeping bag cover provides weather protection and adds an extra layer of insulation. They are usually wind and water proof or at least wind and water resistant to help retain heat. Some sleeping bags can be used without a cover and that might be an advantage on warmer nights when you actually need to shed some extra body heat.
Click on this link for more another view on How To Choose A Sleeping Bag,
Sleep well!