Sleeping Bag Buying Guide
Choosing the Right Sleeping Bag
After a long day outdoors, your sleeping bag is one of the most important parts of your camping equipment. Choosing the right one can make the difference between a comfortable night's sleep and a cold, restless one.
There isn't one sleeping bag that's right for every trip. A summer campsite, a lightweight backpacking trip and a cold-weather expedition all place very different demands on your sleeping system.
When choosing a sleeping bag, consider:
- the temperatures you expect to encounter
- down or synthetic insulation
- weight and packed size
- the shape and fit of the bag
- where and how you'll be carrying it
- the sleeping mat you'll use underneath it
Down or Synthetic Sleeping Bag?
One of the first decisions is the type of insulation.
Most insulated sleeping bags use either down or synthetic insulation. Both can provide excellent warmth, but they have different characteristics.
Down Sleeping Bags
Down insulation comes from the fine insulating plumage found beneath the outer feathers of waterfowl.
Its structure traps a large amount of air relative to its weight. This creates an effective insulating layer while remaining lightweight and highly compressible.
Advantages of Down
Down sleeping bags can offer:
- excellent warmth for their weight
- very small packed sizes
- high compressibility
- excellent loft
- long service life when properly cared for
These qualities make down particularly attractive to backpackers and others who need to minimise the weight and volume of their equipment.
Disadvantages of Down
Moisture requires greater consideration with down insulation.
When untreated down becomes wet, the clusters can stick together and lose loft. This reduces their ability to trap insulating air.
Modern sleeping bags may use water-resistant outer fabrics or treated down to help reduce this problem, but a down sleeping bag should still be protected from becoming saturated.
Down also requires more careful washing and drying than most synthetic insulation.
Don't leave a down sleeping bag tightly compressed for long-term storage. Once home, allow it to loft and store it according to the manufacturer's instructions.
Synthetic Sleeping Bags
Synthetic sleeping bags use man-made fibres designed to trap insulating air.
Modern synthetic insulation can provide excellent performance and has several practical advantages, particularly where damp conditions are likely.
Advantages of Synthetic Insulation
Synthetic sleeping bags generally:
- retain more of their insulating ability when damp
- dry more quickly than down
- are relatively straightforward to care for
- can provide good performance in wet or humid environments
For camping where equipment is regularly exposed to moisture, these characteristics can be particularly useful.
Disadvantages of Synthetic Insulation
For an equivalent level of insulation, synthetic sleeping bags will often be heavier and bulkier than high-quality down alternatives.
The difference varies considerably between products and insulation technologies, so compare the specifications of individual bags rather than assuming all synthetic or down bags will perform identically.
Understanding Sleeping Bag Temperature Ratings
Temperature ratings are more useful than simply describing a sleeping bag as a summer, three-season or winter bag.
Many sleeping bags display several temperatures rather than a single rating.
Depending on the testing standard and manufacturer, these may include ratings such as comfort, limit and extreme.
As a general principle:
Comfort provides an indication of the temperature at which a typical colder sleeper may remain comfortable.
Limit relates to a typical warmer sleeper using the bag in a curled position.
Extreme is a survival-related rating rather than a recommended temperature for normal sleeping.
Don't choose a sleeping bag with the intention of routinely sleeping around its extreme rating.
Temperature ratings are also guides rather than guarantees. Individual metabolism, clothing, food, fatigue, wind, humidity, shelter and the insulation underneath you can all influence how warm you feel.
What Do Sleeping Bag Season Ratings Mean?
Sleeping bags are also commonly described using season ratings.
You'll typically see descriptions such as summer, two-season, three-season or four-season.
These are useful as a quick indication of intended use, but they are less precise than properly stated temperature ratings.
A three-season bag from one manufacturer may not provide exactly the same thermal performance as another manufacturer's three-season bag.
When comparing products, look at the actual temperature information as well as the season description.
Sleeping Bag Shape
The shape of a sleeping bag influences warmth, weight and comfort.
Mummy Sleeping Bags
Mummy-shaped bags taper towards the feet and normally include a shaped hood.
Reducing the amount of unused internal space can improve thermal efficiency and reduce the amount of material required, making this design popular for backpacking and colder conditions.
Rectangular Sleeping Bags
Rectangular bags provide more room to move and can feel less restrictive.
They're particularly popular for campsite and vehicle-based camping where maximum warmth-to-weight performance and minimum packed size are less important.
Some can also be opened fully and used more like a duvet.
Other Shapes
Manufacturers also produce designs that sit between traditional mummy and rectangular bags, offering additional space around the body while retaining some of the thermal efficiency of a tapered design.
Getting the Right Size
A sleeping bag needs enough space for you to sleep comfortably without containing a large amount of unnecessary space that your body then has to warm.
Check the manufacturer's recommended user height and dimensions.
Very tall users should look for longer versions where available, while smaller users may benefit from a shorter bag rather than carrying and heating unnecessary space.
Fit can also be particularly important around the shoulders and feet.
Weight and Packed Size
If you're camping next to your vehicle, sleeping bag weight may have little importance.
If you're carrying everything in a rucksack, both weight and packed volume become much more significant.
This is one of the areas where down insulation can offer a substantial advantage because it can provide considerable insulation while remaining highly compressible.
However, price, moisture resistance and intended use may make a synthetic bag the better choice for some trips.
Choose according to how you'll actually use the bag rather than concentrating on weight alone.
Don't Forget Your Sleeping Mat
Your sleeping bag is only one part of your sleeping system.
When you lie in a sleeping bag, the insulation beneath your body is compressed and becomes less effective. Your sleeping mat therefore plays an important role in reducing heat loss to the ground.
A very warm sleeping bag used with an inadequately insulated mat can still leave you feeling cold.
For colder conditions, consider the insulation provided by your sleeping bag and sleeping mat together.
See our Sleeping Mat Buying Guide for more information about choosing a mat and understanding R-values.
Sleeping Bag Liners
Sleeping bag liners can perform several useful functions.
One of the simplest is hygiene. A liner provides a washable layer between you and the sleeping bag, reducing the need to wash the bag itself as frequently.
This can be particularly useful because a liner is generally much easier to wash and dry than an insulated sleeping bag.
Depending on the material, a liner may also:
- provide some additional insulation
- improve next-to-skin comfort
- be used on its own in very warm conditions
- provide a lightweight sleeping layer when travelling
Different liner materials offer different characteristics. Lightweight liners are useful where minimum weight is important, while thermal liners are designed to add more warmth.
Be cautious of treating claims that a liner adds a particular number of degrees or turns a sleeping bag into a specific additional "season" as universal. The effect will vary according to the liner, sleeping bag, user and conditions.
Keeping Your Sleeping Bag Dry
Whatever insulation you choose, keeping your sleeping equipment dry is important.
When carrying a sleeping bag in a rucksack, consider using a suitable waterproof dry bag or pack liner rather than relying solely on the sleeping bag's normal stuff sack.
At camp, avoid placing your sleeping bag directly onto wet ground and protect it from condensation and rain.
If the bag becomes damp, dry and air it as soon as conditions allow.
Storing Your Sleeping Bag
Compression sacks are extremely useful when transporting a sleeping bag, but long-term storage is different.
Keeping insulation heavily compressed for extended periods can reduce its ability to loft effectively.
Follow the manufacturer's storage instructions. Many sleeping bags are best stored uncompressed or loosely contained in a larger breathable storage bag.
Make sure the sleeping bag is completely dry before putting it away for any length of time.
Which Sleeping Bag Should I Choose?
Start with the conditions in which you realistically expect to use it.
For warm-weather campsite use, comfort and space may matter more than minimum weight.
For backpacking, weight and packed size become increasingly important.
For damp conditions, the moisture tolerance and relatively quick drying of synthetic insulation may be particularly useful.
For lightweight trips where pack size matters, down can offer an excellent warmth-to-weight ratio.
For cold conditions, pay close attention to the temperature ratings and make sure the rest of your sleeping system — particularly your sleeping mat — provides suitable insulation as well.
The best sleeping bag isn't necessarily the warmest, lightest or most expensive. It's the one that provides an appropriate combination of warmth, weight, packed size and practicality for the conditions in which you intend to use it.