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Cars & travel.

Updated: 8 Jul 2021

Sleeping bag buying guide

Our guide to the most important sleeping bag features and best sleeping bag shapes.
Which?Editorial team
How to buy the best outdoor clothingsleeping bags 441006

Different occasions need different requirements from your sleeping bag, but, in general, you’ll want it to be comfortable, suitable for the climate conditions and convenient to pack away and carry.

When it comes to comfort and warmth, there’s no ‘one size fits all’ solution. So how do you know which bag is best for your needs? We’ve put together a few pointers to help you make an informed choice.     

Sleeping bag temperature ratings

The most basic requirement of a sleeping bag is to keep you warm, and just like a duvet’s tog rating, different sleeping bags have different temperature ratings. You may find the bag is given a rating in degrees, either as a limit, or a range of temperatures. For example, a limit of -8oC means it should keep you warm down to external temperatures of -8oC.

Other bags may have a more generalised ‘season of use’ rating, which is designed to give you a rough idea of whether it’s suitable for summer (rated as 1 season), through to year-round use (rated as 4 season).

Some of the lower budget bags don’t have any rating – these are generally lightweight and suitable for occasional summer use.

However, it’s important to note that any ratings are only a guide, as individual requirements and preferences vary. Some people may simply prefer their bag to be as warm as possible, and seasoned outdoor travellers are less likely to feel the cold than someone who rarely sleeps anywhere without central heating.

See our reviews of family tents and head torches.

Best type of sleeping bag filling

  • Synthetic filling is the cheapest choice and has a number of advantages over duck or goose down. The main three being that it’s cheaper, it’s washable and it dries out quicker if it gets wet. These three facts alone make it a good choice for most occasions.
  • Goose or duck down is warmer than synthetic filling, and it can last longer because it’s better at coping with the repeated compressions and ‘squashing’ into your pack that can degrade synthetic fibres. But it can lead to problems if your bag happens to get wet while you’re putting up your tent because it’s slow to dry out; a damp sleeping bag means you’re likely to have a cold and uncomfortable night’s sleep. It’s also expensive and needs specialist cleaning.

If you’re worried about the ethics of using down, you’ll need to be aware that some may be sourced from birds that have been force-fed to make fois gras – so you may want to do further research to ensure the down is obtained from a source that you find acceptable.

Sleeping bag shapes

  • Rectangle: The most basic shape, and familiar from many a childhood sleepover. They’re usually cheap, and are good for those who like their head and neck to have plenty of room. The down side is that cold air can get in round your shoulders.
  • Mummy: These are designed to fit more snugly than a rectangle and are tapered towards the foot. This reduces air movement around your body and helps to build up an insulating layer of warm air, to keep you warmer. Sometimes you’ll find they have a hood and a neck baffle to stop cold air entering the bag. However, the shape and fit of mummy-style bags can be restrictive, so you may find them uncomfortable if you tend to move around a lot in your sleep. The hood will keep you much warmer if it’s cold, but some people find them quite claustrophobic.
  • Pod: If you like to curl up in the foetal position, or simply find other bags too tight, a Gelert Sleeping Pod is a wide oval shape.

Whatever sleeping bag you choose, you’ll still need a sleeping mat underneath you, not just for softness and comfort, but also to protect you from cold ground.

How to care for a sleeping bag

Those with synthetic fillings are generally washable, although unless you have a large drum washing machine at home you may need to take it to a launderette.

Using a removable liner can help to keep the bag clean inside, as this can be washed regularly without the hassle of having to wash and dry the whole sleeping bag.

If you can’t - or don’t want to - clean the whole bag, the outer fabric can usually be spot-washed with a damp cloth to remove stains.