How to choose a sleeping bag

Choose your sleeping bag

After a long day of exploring a good night’s sleep is essential. The right sleeping bag can keep you warm and balance cost with performance.

Sleeping temperature ratings

Temperature ratings give you a general idea about performance and are useful for comparing bags. When you’re outside though, lots of other factors influence how warm you sleep: hydration, how much you’ve eaten, fatigue, humidity, wind and dampness. Altitude is a factor. For every 1000 metres of elevation gain, you’ll experience about a 10°C drop in temperature).

MEC uses the industry-wide EN standard to measure and report the thermal capacity of our bags. The test is performed in controlled conditions at an external, certified lab, using a heated mannequin (wearing a base layer and hat) placed on a 1-inch pad. The reported number is realistic, but is highly specific. It represents the temperature that an average-sized man can sleep in a curled position for eight hours without feeling cold. Women, or people who tend to sleep cold, might choose a bag that’s rated a few degrees warmer than the temperatures they’re likely to encounter, or add a sleeping pad with a high thermal rating.

Read more tips about Staying warm and sleeping warm

Category Temperature
Summer 0°C to 15°C
3-Season -2°C to -15°C
Winter -15°C to -40°C

Synthetic VS. down insulation

The type of insulation, or fill, affects how warm a bag is, but the shape, the way it’s sewn and the features added will also make a big impact on its performance.


Most synthetic fills use polyester threads spun in continuous long filaments mixed with short pieces, called staples. Many bags contain a mix of thinner and thicker pieces, as thinner threads fill empty spaces and trap warm air effectively, while thicker strands provide loft and durability. The fibres will eventually begin to compress and lose some of their loft over time, so synthetic-fill bags don’t tend to last as long as down bags.

  • Pros: Inexpensive. Warm when wet. Hypo-allergenic. Easy to wash and maintain.
  • Cons: Heavy. Less compressible. Loses loft over time.


Down insulation is made up of thousands of plumules – fluffy filaments that line the underside of waterfowl feathers. The quality of down doesn’t depend on the type of bird it came from, but on the bird’s environment. Birds respond to cold conditions by growing fluffier, warmer down. Whiter down is generally more expensive, as it can be used with light coloured or translucent fabrics without showing through, but performance-wise, it’s the same as darker coloured down.

If you regularly wash your bag and store it un-compressed, a down bag will last and retain its loft for decades, so it’s a good long-term investment if you plan to use your bag frequently. It must be kept dry to be effective though, so for extended trips, alpine missions or anywhere that dampness is likely to accumulate, down insulation might not be the best choice.

  • Pros: Lightweight. Compressible. Maintains loft over time.
  • Cons: Expensive. Loses warmth when wet. Requires careful washing.

Down fill-power is a good indicator of quality. It’s expressed as the number of cubic inches an ounce of down displaces. Higher fill-power provides more warmth for the same weight. About 500 is good, 600-700 is better and above 700 is excellent.

Responsible Down Standard

MEC uses down that meets the Responsible Down Standard for all our sleeping bags and jackets. Down is harvested from ducks and geese that are being prepared for sale as food.To ensure the birds are ethically treated and no live plucking or force feeding occurs, third party auditors use a traceable system to verify that animal welfare standards are being met throughout our supply chain. We pay a premium to buy down only from certified locations whose down supply can be traced.

Shape and construction

The shape of a bag significantly affects its warmth, how heavy it is and how small you can pack it. The length you choose should correspond with your height. Having a few extra inches is fine, but if your bag is considerably longer than you, you’ll have unused space to heat and you’ll feel colder as a result. You can use spare, dry clothing to fill gaps around your body if you’ve borrowed or rented a bag that turns out to be too big.

Women’s bags are usually sized slightly shorter than men’s or unisex bags. They are also cut narrower through the shoulders and wider through the hips. Often they have extra insulation in areas where women tend to feel the cold, in the footbox and around the upper body.


Mummy bags are designed to save weight and maximize heat retention. The tapered, narrow shape reduces the space inside the bag that your body has to hear. Most have an integrated hood that you can cinch closed over your head to keep heat inside. They offer superior warmth to weight than a roomier bag. However, some people find them too constricting to get a good night’s sleep.

  • Lightest weight
  • Smallest packed size
  • Most thermally efficient shape


A more relaxed shape than a mummy bag, they are more spacious and may or may not have a hood attached. They are a good, middle-way compromise if you like to sprawl a bit when you sleep, but still want a light, compact bag.

  • Heavier
  • Less compressible
  • Less thermally efficient than a mummy bag


Great for warm weather, a rectangular shape is the roomiest option, but the shape creates additional space inside that bag that your body has to heat so they are not as efficient as narrower bags. They are best for car camping and for sleeping out when the temperature stays above zero.

  • Least thermally efficient
  • Roomy and can be opened as a comforter
  • Heavy and not very compressible
  • Easy to zip two bags together

Loft and volume

These are industry standard measurements that allow you to reliably compare sleeping bags. Loft is a measure of how puffy a sleeping bag is. If two bags have the same fill type, features and shape, the one with the higher loft will be warmer. Volume is a measurement of how small the bag is after it’s been stuffed into a standard sized cylinder with a standard amount of pressure. You might be able to pack your bag smaller than this standard, but if you do, make sure to shake it out well and give it time to regain its loft before you go to sleep.

Sleeping systems

Using a sleeping pad is key to having a warm, comfortable night out, without one, heat is drawn away by the cold ground and the bag’s performance is compromised. Temperature ratings assume you’re using a pad. If you camp out frequently and encounter a wide range of conditions, it might make sense to buy a lighter sleeping bag and add a thicker sleeping pad, combine two pads, use a bag liner, or add an overbag to extend the comfort range. Read more about Choosing a sleeping pad


A sleeping bag liner is a great way to make your sleep more comfortable. They can add a couple of degrees or warmth, but most are designed to wick moisture and keep your sleeping bag clean. A vapour barrier liner is a specialized piece of gear, used in below-freezing temperatures to move the condensation point outward so moisture doesn’t accumulate within the bag itself. They are particularly useful for extended trips when it’s difficult to dry gear thoroughly.