Understanding Sleeping Bags for Multi-Stage Racing and Trekking


Choosing a sleeping bag can be confusing and the prices vary greatly. How do you know what is right for you with so much to choose from? In this article we will try to help you iron out the creases and pick a bag that is right for you. 

We will discuss the technical properties you should be aware of and what bags might be suitable if you are planning an upcoming multi-stage race or a trek in the mountains. 

Down Fill Power Explained

You may have heard of Down Fill Power. Fill power measures the fluffiness of the down or its ability to resist compression. This relates this to how well the down insulates. A Fill Power Rating of 850+ indicates that a 30g sample of down (or an ounce depending on test standard) will occupy at least 850 cubic inches when subjected to a standard compression force. The fluffier the down is, the more air it can trap and the more insulating it will be. What follows from this is that the higher the fill power of the down, the warmer the sleeping bag will be for a specified weight (not taking into account other properties such as shell fabric, zips, shape, stitch construction etc). If you are chasing every gram this is relevant as you can get a lighter sleeping bag with the same warmth as a heavier one if you choose a bag with higher fill power.

Fill power. Equal weight of down in each sample but different volume due to the “fluffiness”

There is one internationally recommended test for fill-power performance and that is the IDFB standard. Some brands and suppliers may conduct their own fill power tests rather than (or in addition to) having the down lab tested and there are other standards that can be used. It is also worth noting that a sample of down is preconditioned before its fill power is tested. The down that goes into your sleeping bag may not have been through the same preconditioning process. Some manufacturers may therefore quote a more conservative and realistic fill power rating which is lower than that of the tested sample, whereas others may be more optimistic in the value they quote. Several manufacturers claim that they use only the very best quality goose down with the highest fill power available, yet their quoted fill power ratings range from 850+ to 1000. This makes it difficult to actually compare like for like. Also, we should take into account that down is a natural, non-homogeneous product which can be mixed in endless combinations.

Read more about down quality on Yeti here: http://yetiworld.com/about/products/crystal-down/

All of myRaceKit’s bags have a high fill power, ranging from 800+ cuin to 900+ cuin. This is because most of our customers demand light weight options. Also, reputable brands with high quality bags will ensure their down is ethically sourced. In some bags you will see a number in the name, for example Lightwave Firelight 550. This number has nothing to do with the fill power (900 cuin in this bag) but is often a reference to how many grams of down is in the product (550 grams). If you compare bags with the same fill power you can get an idea of their relative warmth by looking at how much filling is in them. Similarly the Yeti Passion Three has approximately 300g of filling and the Yeti Passion Five 500g. If two bags have the same fill weight but different fill power, the bag with the higher fill power will be warmer. Therefore, looking at the weight of a sleeping bag alone will tell you very little about how warm it actually is.

Temperature Rating Explained

Most manufacturers will now use the EN 13537 standard which provides three temperature ratings for the bag:

  • Comfort — the temperature at which a standard woman can expect to sleep comfortably in a relaxed position.
  • Limit — the temperature at which a standard man can sleep for eight hours in a curled position without waking.
  • Extreme — the minimum temperature at which a standard woman can remain for six hours without risk of death from hypothermia.

The temperatures assume that the person is clothed, using a quality sleeping mat and is hydrated and nourished.

Not all manufacturers have their bags tested according to the EN standard and there may be varying reasons for this. Some may claim it doesn’t provide an accurate picture of the bag’s performance, others may find the cost of having the bags tested prohibitive, and some may not want a like for like comparison with their competitors. Where brands have their own way of providing the rating, try to understand how this may compare to the EN rating by reading the small print. Comparing the weight, down fill power and characteristics of the bag may also help.

Choosing a bag

Now we’ve covered some basics, let’s look at some of the factors you may want to consider when choosing your bag.

  1. Cold or warm sleeper?
  2. The race setup & rules
  3. Climate: dry or humid?
  4. Night time temperature & accommodation type
  5. Your sleeping system as a whole
  6. Your race ambitions
  7. Future races or events
  8. Your height / size
  9. Any specific preferences regarding the sleeping bag design or materials
  10. Your budget
  11. Examples of suitable bags for various activities

Cold or warm sleeper?

Do you normally feel the cold or are you quite “hardy”? If you do feel the cold then we suggest avoiding the very lightest bags unless you are going somewhere where you know night time temperatures will be mild.

Race setup & race rules

By race setup we mean whether the race is completely self-sufficient or whether your luggage is transported from camp to camp. If you need to carry your sleeping bag, weight will be an important factor. If you don’t need to carry you bag, you don’t have the same restriction on weight and volume although some races may dictate a maximum weight for your transported kit bag. Some races, such as the Grand to Grand, will have minimum requirements on the rating of your sleeping bag. If this is the case, clarify what rating is referred to (typically Extreme rating), and then narrow down your options accordingly. Do note however that just because the race recommends a minimum rating it doesn’t mean that you will be warm in a sleeping bag of that rating. Sleepless nights because of cold are detrimental to performance and it’s a false economy to save a couple of hundred grams at the expense of your recovery.

The same can be true for a trek. Will you be self-sufficient or will you have a Sherpa or organisation transporting your luggage? This can make a big difference, particularly if you need a warmer bag. Weight and volume will differ significantly based on down fill power for the same warmth and rating.

Climate: dry or humid?

Down will perform best when it comes to insulating in a dry environment. However, if you are going somewhere where conditions are damp you may want to consider a synthetic sleeping bag or alternatively a down bag which has been filled with water repellent down. Synthetic sleeping bags are now available in very light weight and packable options, at least for warmer conditions.

The likely night time temperature & accommodation type

Try to understand what the likely temperature at night will be but also consider what the difference in temperature is between night and day. Even if the actual temperature is not that cold it may feel colder because the day was really hot. The accommodation type provided in race camp can make a big difference. For example, in Marathon des Sables, the tents have two open sides and strong winds are not uncommon. Other races may provide more sheltered accommodation such as more sophisticated tents or even your own exclusive one-man tent. If you are completely sheltered from wind you won’t be as cold. In some races the altitude may vary significantly over the course of the week. In these cases it may be a compromise and you may need to accept being either too cold a few nights or too hot a few other nights. Other factors that influence how much you feel the cold are hunger and tiredness.

If you trek in Nepal you may sleep in lodges but these are typically not insulated nor do they have any heating. It is not uncommon to wake up with frost on the inside of the window and below zero degrees in the room.

Your sleeping system as a whole

Leading on from the above point, your sleep is made comfortable by more factors than your sleeping bag. A quality, insulated sleeping mat adds significant warmth. This can be an inflatable mat or a quality foam mat. Uninsulated air mattresses will not add warmth, nor will cheap, thin foam mats. A light-weight inflatable pillow adds comfort. Think twice before you save weight by not taking a sleeping mat. Try to find out as much as you can about the ground in race camp. For example, in Marathon des Sables it is quite rocky and hard, whereas in Oman it is sandy and softer and warmer at night. Some races, such as the Everest Trail Race, provides sleeping mats in tented accommodation or you might spend a night in a tea house where you will have a simple bed but no heating and temperatures may reach well below zero degrees C at night.

Other ways of adding warmth to your sleep system is to have a light weight down jacket or wear a warm base layer. A hat can also help. Another way of adding warmth is with a silk liner or a synthetic liner which can add anything between 5 and 10 degrees C. Do note however that you will be warmest in your bag if the warm air from your body can fill the bag so wearing more clothes may prevent this. A snug fitting sleeping bag, without excessive extra room, and a thin base layer is optimal for warmth.

Your race ambitions

It goes without saying that your race ambitions come into play. If you want to race at the front you have to sacrifice some degree of comfort for weight saving. This is where the higher quality down sleeping bags can really make a difference (as can the lightest weight synthetic bags). Look at high fill power and few features to maximise the warmth you get for the weight. That said, everyone who is doing a self-sufficient race, carrying their gear, will need to think about the weight of their pack. It all adds up, so the lighter you can go the better! Don’t forget to balance the weight with the recovery. If you sleep well you will race better. Pack light, but pack right…

Future races or events

A sleeping bag can be a big investment. If you already have future races planned where you will need it again, try to get a bag that will be suitable for these as well. Or, consider how to make your system flexible.

Your height / size

The closer you can match the size of the bag to your height the better. Both for reasons of comfort (if you are tall) and in order to maximise insulation (avoid excess space in the bag) and avoid carrying excess weight. Some brands, such as Yeti offer M to XL sixing in all bags. Some brands offer small sizing though this is less common. A sleeping bag should fit comfortably and not restrict your movement. You should be able to stretch out your toes without the hood coming off. Most brands will indicate what height range their respective sizes are suitable for.

Any specific preferences regarding the sleeping bag design or materials

You may have preferences when it comes to the sleeping bag’s stitching construction, zip length, or other features. A full zip can provide good flexibility, especially if you are a warm sleeper or if you want it to be easier getting in and out of the bag. Or, you may, for any number of reasons, not want a down sleeping bag but limit your search to only synthetic bags.

Your budget

Your budget may be a limiting factor. We encourage you to consider the points above and compare what you get for your money before making the decision. A suitable sleeping bag doesn’t have to cost a fortune but as with all other things there are always compromises.

Examples of suitable bags for various activities

Comfort Rating approximately +12 to +14 degrees C

If you are embarking on Marathon Des Sables and don’t mind possibly being cold, you can get away with the lightest bags. Great examples here include the Yeti Fever Zero, Sea to Summit Spark SP1, OMM Mountain Raid 1.0,or 1.6 or 160, Nordisk Oscar +10, Haglofs L.I.M +13, or the Yeti Passion One. These bags would also be suitable for summer activities in general as long as you are not at altitude. If you know that you will be in a humid or rainy environment, consider the synthetic options.

Comfort Rating approximately +4 to +9 degrees C

If you are a cold sleeper you will want to look at a slightly warmer bag for Marathon des Sables. You will then also have a bag that could be suitable for races like the Grand to Grand, some of the 4Deserts races, Fire and Ice in Iceland, The Namibian Crossing or for warmer summer trekking in the mountains. Suitable bags here include Western Mountaineering Highlite or Summerlite, RAB Neutrino 200, Yeti Passion Three, Oscar Zero -2, or the Yeti V.I.B 250.

Comfort Rating approximately -7 degrees C to -2 degrees C

If you are embarking in a race or trek at higher altitude the nights will be significantly colder. Examples include Trans Atlas Marathon in Morocco, Everest Trail Race in Nepal, Atacama Crossing in Chile, trekking in Nepal, racing or trekking in other high mountain ranges such as in Nepal, the Alps, Peru, or climbing Kilimanjaro. Here you need a warmer bag and suitable examples include Yeti Passion Five, Lightwave Firelight 550, 650 or 750. If you climb Kilimanjaro we would definitely recommend the Firelight 750. The Firelight 650 is very suitable for the popular trek to Everest Basecamp.


As we always say there is no one size fits all when it comes to gear for your multi-stage racing and that is certainly true for sleeping bags. You should always check the race or trek organisers’ recommended and compulsory kit lists, and research the weather for the season when you are going. See our full range of sleeping bags here.

Understanding Sleeping Bags for Multi-Stage Racing and Trekking
Article Name
Understanding Sleeping Bags for Multi-Stage Racing and Trekking
Choosing a sleeping bag can be confusing and the prices vary greatly. How do you know what is right for you with so much to choose from? In this article we will try to help you iron out the creases and pick a bag that is right for you.
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