How To Choose a Sleeping Bag

A sleeping bag is a major purchase and your choice can mean the difference between a good night's sleep and several hours of damp, cold misery or in extreme circumstances much worse. This means that when you come to decide on a bag it's important to ask yourself as many questions as possible about just how you'll use it. In this guide I'll try and show some of the main considerations and highlight a few scenarios in which your choice of bag would be particularly important.

First ask yourself these questions:

  1. How cold is it likely to be where you'll be using the bag and how much do you feel the cold?
  2. What other conditions is the bag likely to face?
  3. How much space do you have for carrying the bag and how much weight do you want to carry?
  4. What is your budget for the bag?

Temperature Ratings

When it comes to sleeping bags the performance figures are always dominated by temperature ratings and as is inevitable the comparisons between manufacturers can be a little murky. The situation is further complicated by the fact that we all have slightly different insulation needs. I sleep fairly warm so I can often get away with a lighter bag where others will need four season insulation. The most important thing is to treat all manufacturers figures as a guide. If you sleep warm then you'll probably be comfortable in a bag somewhere below it's comfort rating but if you sleep cold you might want a bag rated a little colder just in case The extreme rating that you'll see on some of our bags is intended to show the minimum temperature at which an experienced user could use the bag to stave off hypothermia: do not expect to sleep in the bag at this sort of temperature.

When thinking about the temperature rating of your bag you also want to consider 2 other factors;

  1. What you'll be wearing inside the bag to sleep in. The temperature ratings on sleeping bags assume that you are dry, wearing full baselayer cover and have had a hot meal for tea. In fact exhaustion levels and your latest meal have a profound effect on how warm you are and have nothing to do with your bag. You could be wearing more or less clothing than the assumed base layers and this change can stretch the usable temperature window of your bag.
  2. What you will be sleeping on. Thermal conductivity into the ground is your major source of heat loss. If you are not currently warm enough then upgrading your sleeping mat may be a better space and cost solution than getting a heavier bag. A Foam or Down filled air mattress is way superior to a closed coll foam mat. Think of your bag and your mat as 2 parts of the same solution. You may wish to read our How to Pick the Right Sleeping Mat advice

Other Conditions

What you're really looking for when considering other conditions is how likely it is that the bag might get wet. For use bivi-ing and open air camping or when you'll be spending a number of days in wet climates it's safe to assume that at some point your bag is likely to get wet. This is one of the most important questions to ask when you're trying to decide between a synthetic and a down bag as down's performance decreases severely when it gets wet whereas most synthetic insulation will shed water and even if it wets out will retain some insulating value. One area where this is a particular concern is alpine bivis and emergency use. The traditional approach to these situations was to take a superlight down bag and GORE-TEX bivi bag whereas with newer synthetics getting lighter and more packable it can be more efficient to pick a featherweight bivi and synthetic bag.

Space and Weight

When it comes to pack size and weight, down is the king. Its remarkable ability to trap air means that for a given temperature rating you can expect a synthetic bag to weigh roughly 1/3 more and be 1/3 larger when packed. However for many camping situations - car camping, holiday use - these considerations may not be relevant. For backpacking think how big a sack you usually carry. If you like to pack light and carry a 30-40l pack for weekend trips then a bulky synthetic will be out of the question but if you're prepared to carry a little more then you may think they're the better choice.

Ease of Care and Durability

Down sleeping bags require more careful care than synthetic bags. The feathers in a down bag are fairly fragile and will gradually lose their ability to loft over time. Occasional cleaning does restore the loft but this is best done by a professional service and the longer between cleaning the better. Synthetic bags are more hardy and can be machine washed at home without damaging the bag and so can be cleaned more often. Neither type of bag likes to be stored long term packed tight in it's stuff sack but this is more damaging to the loft ability of down feathers. So synthetic bags are good for dirty environments where regular cleaning will be necessary and will outlast a down bag.


One final distinguishing factor between down and synthetic fills is that the labour intensive process of producing, sorting and grading down means that it is more expensive than man made equivalent. A down bag can cost as much as £100 more than an equivalent synthetic. This is further exacerbated by the fact that down requires specialist cleaning which can be costly.

So which bag is for me?

Choosing a bag is always going to be a compromise, no one bag can do it all. Here are some general starting points for various types of user:

Car camping and summer wild camping
For those who don't camp that often and for whom weight is not such a concern, a synthetic bag represents excellent value for money. The addition of a silk liner will add versatility and warmth. The Mammut Kompakt, Rab Ignition and Mountain Equipment Starlight ranges are ideal.

General Backpacking and Summer Mountaineering Use
For most users who are interested in backpacking and mountaineering a midweight down bag is probably the best choice. This will be capable of everything from valley camping in mid-winter to long summer expeditions with only the very warmest and coldest days outside it's comfort zone. Its usability can be further extended with a silk liner for insulation when it's cold or to use on its own when it's too warm. The Mountain Equipment Classic range is a good starting point. Hybrid bags, such as the Mountain Equipment Matrix range, and bags with hydrophobic down, such as the Rab Neutrino Endurance range are also available, the idea being that you get many of the benefits of a down bag without having quite as much of the drawbacks in damp conditions.

Adventure Racer/Mountain Marathon/Solo camper/Ski Touring
For those who need the lightest and tiniest bags, Down is the usual way to go and the higher grade the down the less you'll need to keep you warm. There are also some specialist Synthetic bags available too. Have a look at the Mountain Equipment Xero, Rab Neutrino for Down bags and the OMM Raid for synthetic.

Alpine Bivi and Expedition Use
If you need low weight and pack-size but great performance and weather resistance then a high quality down bag with a more weather resistant outer shell is the best bet. For greater versatility but more weight and cost use a bag from the range above combined with a bivi bag. The Rab Neutrino Endurance range has hydrophobic treated down, whilst the Mountain Equipment Matrix range uses a mix of synthetic and down for insulation. The Mammut Alpine range are lightweight synthetic bags for alpine use and the Mountain Equipment Extreme range for more serious expeditions.

And Finally...
If after considering all the above you're still unsure what to look for in a bag or you just need more advice then please call us and we’ll be happy to offer you any help we can. Contact details just below in the page footer.