Choosing a Sleeping Bag

Gear selection

When assembling your hiking kit for overnight or multi-day hiking the tent, sleeping bag, and pack are generally the three heaviest and often the most expensive individual pieces of equipment you carry and together they make up what is known as the Big Three.

When it comes to choosing a sleeping bag the problem is the huge range of choice we have available on the market. There are hundreds of bags available in the retail stores and online but when choosing a sleeping bag there are a few key considerations that come into the mix to help you make your decision. These include:

  1. Warmth: Ensure your chosen bag will cater for your typical hikes
  2. Bag shape:  a balance between comfort and warmth. The less airflow the warmer the bag but it may also mean less room to move
  3. Fill material – Down versus Synthetic
  4. Features – the sky is the limit here
  5. Weight and size – light and compact is better particularly for carrying
  6. Your budget – buy the best bag you can afford


The first decision you need to make when choosing a sleeping bag is what level of warmth do you need? This is not as simple as it sounds and is based on your own personal tolerance to cold as well as the expected minimum and maximum temperatures.

One helpful piece of information you can use in your selection is the European sleeping bag standard, ISO 23537-1:2022. The standard is a European system accepted worldwide to standardise the temperature ratings of sleeping bags manufactured or sold in Europe. This standard helps you to directly compare one sleeping bag to another regardless of what label the manufacture chooses.

The ISO 23537-1:2022 system uses standardised temperature tests using a thermal manikin with heaters and temperature sensors to measure the insulation value of a sleeping bag. These tests are carried out with the manikin wearing one layer of long underwear, which is placed inside the sleeping bag on an insulating pad typical of those used when camping. The test is conducted in a temperature-controlled chamber and a range of ‘comfort temperature’ is derived from measuring the energy required to maintain a stable temperature. Four figures are derived from these tests:

  • Upper Limit
    • This figure is not normally shown on sleeping bags and is the temperature at which a ‘standard man’ can sleep without excessive perspiration
  • Comfort
    • This is the temperature at which a ‘standard woman’ can expect to sleep comfortably in a relaxed position. If you are a male and a cold sleeper use this rating to decide the coldest temperature for which the sleeping bag is suitable
  • Lower Limit
    • The temperature at which a ‘standard man’ can sleep for eight hours in a curled position without waking. If you are a warm male sleeper you can use this rating to decide the coldest temperature you can use the sleeping bag
  • Extreme
    • This is a survival only rating for a ‘standard woman’. Between the lower limit and the extreme rating, a strong sensation of cold has to be expected and there is a risk of health damage due to hypothermia or possibly frostbite. This is an extreme survival rating only and not intended for regular use

When using this standard to choose a sleeping bag think about whether you are a warm sleeper or a cold sleeper, and what sort of clothing you usually wear for sleeping when you’re camping.

One thing to note here is the description of a ‘standard man’ and ‘standard women’, the ISO 23537-1:2022 system specifies age, weight and height which does ensure consistency when testing but really there is no such thing. From my perspective I have a high cold tolerance while my wife Gill has the opposite issue. I can usually get away with a sleeping bag that is rated for warmer conditions than those in which I am camping. Given the amount of hiking and camping I do, I  run multiple bags and after a number of years of testing and trial and error I use a -2º Celcius bag for all but the coldest of my hikes when I swap over to a -4° Celcius bag.

If you have decided to buy just one bag to meet all your camping needs, which is what most hikers will do then it is likely you will be making a compromise. If this is the case, the compromise needs to err on the warmer side. It is better to be too warm as you can always open the zip or reduce clothing you are wearing. If you go for a bag that won’t cope with cold conditions then you run the risk of being uncomfortable at best or of getting hypothermia, which can have serious repercussions for your health at worst.

Sea to Summit Ascent II temperature ratings as measured under the ISO 23537-1:2022 system. In the case of this bag the ‘average male’ will be comfortable down to -10° Celsius while the ‘average woman’ will only be comfortable down to -4° Celsius


The second main factor when choosing sleeping bags is their shape with three main shapes being readily available. Essentially the less air space inside the bag, the warmer the bag tends to be. These choices are:

  • Rectangular
    • Lots of space, usually bulkier and heavier
  • Mummy or form fitting
    • Minimal space, which may be uncomfortable for larger people and/or restless sleepers but warmer due to the limited airflow
  • Tapered rectangular
    • A combination of the two types above that provides more space at the expense of a greater airflow but not as much as a full rectangular bag

Most hikers  (as opposed to campers) will choose a tapered rectangular bag or mummy style depending on their personal preferences.

Sleeping bag shapes (images from Sea to Summit)

Down versus Synthetic

Once you have decided on the temperature range and shape then your second choice is the type of insulation material in your sleeping bag. Currently there are two main choices of insulation material available on the market:

  • Down
  • Synthetic

Down is derived mainly from ducks or geese with geese down usually providing the best quality although this is becoming harder to source. The second option is a synthetic manufactured material. Both insulation materials have their advantages and disadvantages, and what you choose will depend on your circumstances.

Down sleeping bags


  • Lightweight
  • Easy to compress to a smaller size
  • Excels in cold, dry conditions
  • Longer life span if looked after


  • Expensive (can be twice the price of a comparable synthetic bag)
  • Slow to dry when wet
  • Doesn’t perform well in conditions where your bag is always going to be wet and where there isn’t a chance to dry out

You will often see descriptors associated with down bags such as ‘loft’ or ‘fill power’ and this describes the quality of the down material. The higher the loft, the warmer and lighter the bag but also the more expensive. The best quality bags have 850+ loft, which will be reflected in the price. Cheaper down bags will have a loft figure that is much lower. The higher the loft number combined with the amount of down will provide a warmer but more expensive bag. The same weight of a higher loft will fill a larger area than a lower loft quality. As an example 1 ounce of 850 loft down will fill 850 cubic inches of space. One ounce of 650 loft down will fill 650 cubic inches of space. In this example you will need a greater of amount of the 650 loft down to achieve the same warmth which means that the bag will be heavier.

Many bags contain down fill that is treated so it is water repellant. The key word here is ‘repellent’ rather than ‘waterproof’ and if you drop your sleeping bag in water then that is a real issue with a down bag.

Down bags are excellent when you know you can maintain a dry bag and want to minimise the bag size and weight e.g. long distance through hiking.

650 loft down versus 850 loft down. In this image both samples of down weigh the same but the 850 loft down expands to a much greater volume so will generate more warmth. You can see that the 650 loft down on the left looks courser while the 850 loft down is much finer. Usually the 850 loft down is from Geese and because this down source is not as common it is more expensive because it is harder to source

Synthetic sleeping bags

The other option for fill in sleeping bags is synthetic materials. While most keen hikers will use down bags synthetic bags have their place.


  • Quick-drying
  • Insulates when wet
  • Non-allergenic
  • Less expensive
  • More robust so often used as school or rental bags


  • Bulkier and heavier when compared to a similar rated down bag
  • Shorter life span than down bags

Synthetic bags are a good choice when you are car camping and when you don’t have to worry as much about the weight or bulk of the bag or when the conditions are very wet.


Bag length: Choose a bag to suit your height. Most manufacturers will advise you of a maximum height for their bags and will often produce different bag lengths to suit different height users. If you are close to the limit on a bag go up a size for added comfort.

Sleeping bag hood: Unless you are choosing a bag for hot summer conditions then most sleeping bags come with a hood as your head is one of the major areas of heat loss.

Draft tubes: Draft tubes will usually cover the zip and form a ring just above the shoulder to limit the movement of air within the bag. The less air movement, the warmer the bag. This feature is often invisible but is very important when looking for a warm bag.

Left or right zip: Many manufacturers will produce bags in a left and right hand configuration to allow them to be joined together. I haven’t seen this done but prefer my own bag at night

Security/stash pocket: Typically located on the chest near the top of the bag and is handy for keeping small valuables or phones/battery packs to prevent them loosing their charge in cold weather.

Zippered foot box: As the name suggests, this feature is a zipper at the foot end of the sleeping bag which is independent of the side zipper. The benefit is that you can unzip the foot in warmer temperatures thus giving you a wider range of seasons that you bag will suit. If you are only using one bag for all your needs get one that will zip fully open


Bags joined together. Some manufacturers offer this feature but I have yet to see anyone using it when out hiking

Security pocket on the inside of a sleeping bag

Weight and size

Always choose the correct sleeping bag based on warmth but once you have gone past that choose the smallest and compact bag so you can to minimise the weight and bulk in your pack. Bags that compress don to a tiny size and have a good warmth rating are usually more expensive

Different size bags compared to a 1 litre water bottle

Budget (Cost versus Value for Money)

I’m a big fan of the term ‘value for money’. Some of Australia’s well known chain stores sell adult sleeping bags for as little as $20. Yes they are cheap but you won’t enjoy your experience because they are not going to keep you warm or comfortable. Everyone has a budget and for most people that will mean having a single sleeping bag. In this instance choose the best bag you can afford to keep you warm at the desired temperatures that you are going to be camping in and with the features that you really want/need.

Always choose the correct sleeping bag based on warmth but once you have gone past that choose the smallest and most compact bag that you can afford so you can to minimise the weight and bulk in your pack.

The Final Word

With so many sleeping bag options available on the market take your time and do you research to narrow down the bag choice before choosing one based on your own specific circumstances. Take your time in making your choices and don’t buy a new sleeping bag based purely on price. Sure that’s a consideration but you are likely to a have a good quality bag for many years and you are better spending just that little bit extra to make sure you get what you really need.

While the focus of this article has been around sleeping bags you will need to consider your ‘sleep system’ which includes your sleeping mat, the clothes you wear to bed and a sleeping bag liner of some type. All of these considerations go towards providing a comfortable nights sleep and if you don’t match your sleeping mat and clothing to your needs then you wont have a comfortable nights sleep and with that you wont enjoy your hike.

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