Whether you’re hiking hut to hut, camping up a mountain or trying to get some kip on an overnight train, your choice of sleeping bag can make, or break, your night
Some bags come in a standard, unisex sizing, which usually means a man’s fit. Women-specific sleeping bags are often wider around the hips, narrower around the shoulders and with extra insulation at the feet. Some men may prefer women’s bags; conversely, taller, slimmer women may prefer a men’s or unisex option.
Every sleeping bag has a temperature gauge. The Comfort level is the one to look for, as this tells you how cool it can be before you start to feel cold – the lower the temperature the better. You’ll notice there’s also a Limit and Extreme temp noted (or variations on these terms). As everyone feels cold/heat differently, use the Comfort figure as a guide to the bag’s limitations.
The ideal bag combines low weight and high warmth. Also, look at how small it packs down in its compression sack – can you fit it in your luggage?
Look for two-way zips that open the length of the sleeping bag, so you can open the bottom end to vent your feet if necessary. Check that there is a good size baffle of fabric and fill behind the zips to keep out draughts.
Bags are usually rectangular or a tapered ‘mummy’ shape. The former offers more space and can be unzipped to make a duvet; the latter, due to its closer fit, is better for heat retention.
Sleeping bags are filled with one of two types of insulation: down (eider, goose or duck) or synthetic (a mixture of man-made fibres).
Naturally light, down insulation generally offers the best warmth-to-weight ratio. It is usually a mix of feathers and down; the higher the down content, the better it will be at trapping warm air, but the more expensive it will be. Manufacturers advertise a ‘fill power’ (e.g. 500, 700 etc.) – the higher the number, the higher the quality of the down and the more efficiently it will keep you warm.
Synthetic insulation can be as warm as down though usually doesn't pack quite as small. It also works well even when wet (when down gets wet it will stop insulating, unless it is hydrophobic). The cheaper the fill (and bag), the less efficient it is likely to be.
Some bags offer extra quirky features – an attached torch, built-in mosquito net, the ability to transform into a jacket. Consider whether these features are important to you. Or would you rather spend your money on an extras-free warmer/lighter bag?
Check out our review of the best sleeping bags in the February 2015 issue of Wanderlust