Whether you're off to the Glastonbury festival or pitching a tent at Base Camp 1, you'll need the right sleeping bag.

This handy guide has been designed to help you get a better night's sleep when you're enjoying the great outdoors.

Sleeping bags can be divided into 3 categories:

Mountain - these specialist lightweight models for alpine use keep weight and bulk to an absolute minimum. They can usually handle temperatures in excess of -15°C. For extreme low temperatures, use with a vapour barrier liner.

Trekking - designed to keep pack size and weight to a minimum, these provide a high level of warmth to weight.

Trail - great for weekends away when pack space isn't critical, a good trail bag should be reasonably light and not too bulky. Choose a synthetically filled model to keep cost down.

The less air there is in a sleeping bag, the less work your body has to do to keep you warm.

There are two main shapes of sleeping bag - mummy (or 'technical') and rectangular (or 'caravan').

Mummy bags - provide the greatest insulation by confining space around the body, so less air can circulate. They also feature a hood to stop warm air being lost from your head - an essential feature in winter or freezing conditions.

Rectangular bags - allow for more sleeper movement.

Stitch-through - this is when insulation is stuffed between two layers of fabric and sewn in.

Offset stitch - these have the seams in the middle, with insulation above and below them.

Synthetic

Less expensive to produce than down, and less prone to losing their insulating properties when wet, these use four typical fillings:

Hollowfibre - easy-to-clean and durable, this is a collection of polyester fibre.

4-hole Hollowfibre - four holes through the centre of each polyester fibre increases the surface area of the hollowfibre, for greater insulation and less bulk and weight.

Quallofil 7 - seven holes through each fibre further increases the insulating material's surface area, making it even more effective at trapping heat.

Micraloft or MTI loft - made from siliconised polyester fibres, these are layered for high warmth without adding bulk.

Down

Lighter and warmer than the equivalent synthetic bags, these are still considered best for winter and expedition use, where low weight and bulk are important. It works by the feathers trapping your own body heat, to create a warm layer of air around you.

Down comes in a number of different qualities and mixes, for example, 40% down and 60% feathers. A higher proportion of feathers will add weight to your sleeping bag, but down is more effective as an insulator.

Down bags lose much of their insulation properties when wet - so care should be taken to keep them dry.

Down sleeping bags require specialist cleaning in order to avoid damage.

There are three main kinds of down:

Duck down - cheaper and weightier than goose down.

Goose down - much finer (and therefore lighter) than duck down, this provides 25% more insulation than duck down.

Hi-loft down - made from very fine goose down, this provides yet more insulation by trapping more air. The table below shows typical lofts.

These are designed to be breathable, so you don't build up sweat or condensation inside the bag. More expensive sleeping bags tend to have more durable, better quality shells - for a more comfortable night's sleep.

When buying a sleeping bag, you need to consider the lowest comfort temperature; you can always sleep with your bag open or remove clothes, but you may not have access to a warmer sleeping bag.

Exactly where you are camping is an important factor in determining the sleeping bag you'll need. For example, if you are up a mountain, you'll need a warmer bag than if you're festivalling in a field.

Remember that wind chill can add considerably to feeling cold, so there will be a difference in temperature whether you're sleeping in a tent, hut, chalet, or out in the open air.