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    • Sleeping Bag Guide

      A fitful night’s sleep is no preparation for the big day ahead. Sleeping bags can make the difference between a comfortable sleep and suffering through the night.

      Aiguille Noire de Peutery, Mont Blanc Massif.

    Temperature Ratings

    There’s nothing exciting abut sleeping bag temperature ratings, but it doesn’t mean they’re not important. Whilst you don’t want to be shivering, you equally want to avoid being too warm or carrying a sleeping bag that is too big and heavy for your trip.

    There are various methods that help to determine the temperature ratings for a sleeping bag. However the Standard methods EN 13537 or ISO 23537 have now been adopted by the majority of sleeping bag manufacturers, including by Mountain Equipment. We played a large part in the development of this Standard and our staff continue to be part of the committee that works on its progression.

    All of our sleeping bags display EN13537 / ISO23537 temperature ratings except our very warmest sleeping bags: our Extreme Expedition sleeping bags and Glacier Expedition bag fall outside the range of the test.

    The EN/ISO tests produce three different temperature ratings:

    • Comfort rating

      This rating is defined as a temperature at which a ‘standard female’ in a relaxed posture will feel comfortable inside a Sleeping Bag. If you are female or a cold-sleeper, this is the temperature rating that is most relevant to you.

    • Limit rating

      This rating is defined as a temperature at which a ‘standard male’ in a curled-up posture can sleep inside the Sleeping Bag without waking for an eight hour period. If you are a male, or are not a ‘cold sleeper’, then this rating is most relevant to you. This is also the rating which is advertised most widely for most sleeping bags.

    • Extreme rating

      This rating indicates the minimum temperature at which a ‘standard female’ can remain for a total of six hours before risking the chance of hypothermia and damage to health. Generally this rating should be treated as a guide to how the Sleeping Bag performs under extreme emergency situations, and should not be considered a factor in making a purchase.

    Good Night's Sleep Guarantee

    In addition to these Standard temperature ratings we also offer our Good Night’s Sleep temperature rating. This is a rating which we feel is the most accurate reflection of a bag’s potential in real-life situations. In most cases our Good Night’s Sleep rating will tally closely to that of the EN/ISO result, but for certain bags the discrepancy might be greater.

    This is because the EN test is strongly affected by certain aspects of a bag’s makeup which don’t make as much difference in real life, such as the face fabric and the shape of the bag. Our Good Night’s Sleep rating is guaranteed and is based on extensive experience of manufacturing sleeping bags and extremely exhaustive testing in the laboratory, during cold chamber testing, and is influenced by user feedback from countless expeditions stretching back more than fifty years.

    We suggest you base your sleeping bag purchase most closely on the Good Night’s Sleep temperature rating, but of course if you think you particularly feel the cold or otherwise, then you should take this into consideration.

    Weight & Pack Size

    Be honest: do you tend to car camp, backpack, or bivvy on ledges? If you mostly camp in places where the pack size and weight of your sleeping bag are not important, then consider buying a bigger, more spacious sleeping bag. But if you are alpine climbing or backpacking and carrying your sleeping bag for an extended period, then a lightweight sleeping bag is really important. Look for a sleeping bag that weighs under a kilo (2.2lbs) for a summer sleeping bag, and under 600g (1.3lbs) if you are really serious about shedding weight. If you are looking for a year-round sleeping bag that’s suitable for a variety of temperatures, then anything up to about 1.5kg (3.3lbs) will suit you perfectly.

    The packed size of a Sleeping bag is closely allied to its weight, but there is also a huge difference between down and synthetic sleeping bags. A down sleeping bag with a Good Night’s Sleep rating of -20°C/-4°F may actually compress smaller than a synthetic sleeping bag with a temperature rating of -5°C/23°F!


    Sleeping bags are either filled with down or with synthetic insulation. Down is warmer for its weight and packs smaller, so is a better choice for those who regularly carry their sleeping bag. Down is also longer-lasting and more comfortable to sleep in. However, synthetic sleeping bags are less expensive than down sleeping bags, they are more effective if the sleeping bag gets very wet, and they are easier to clean and launder. For most performance applications, down is superior to synthetic, but if you expect exceedingly wet conditions, then synthetic is the way to go.


    Synthetic insulations might all look similar to the untrained eye, but they vary greatly in their warmth, softness, compressibility, durability, water resistance and compression recovery.

    The warmer the synthetic sleeping bag, the more weight of synthetic insulation it has inside it, usually in the form of a greater number of layers of insulation and/or thicker layers of insulation.

    Our range of Polarloft® synthetic insulations used in our Sleeping bags are a result of scouring the globe for the best possible materials. They offer a fantastic blend of warmth, comfort, compressibility, and durability which is ideal for all but the most demanding situations.


    The greatest factor determining how warm a down sleeping bag will be is the fill weight: how many grams of down are in the bag. The measure of the quality of that down is the fill power, with a greater number indicating greater quality. Roughly speaking, down above 700 fill power is very good down, down above 800 fill power is exceptional down. We use three different types of down in our sleeping bags:

    • 800 Fill Power Goose Down

      Our very best Eastern European goose down. Sourced from Ukraine and DOWN CODEX™ approved. Amongst the best downs available anywhere.

    • 700 Fill Power Duck Down

      Sourced from two suppliers, one in Poland and one in China, both of which are DOWN CODEX™ approved. An extremely good all round down insulation.

    • 700 Fill Power Recycled Down

      Taken from post-consumer down products, cleaned, sterilised, and sorted to leave an excellent down insulation.

    Grey Down and White Down

    Depending on the source birds, down may be grey or white in colour. Grey down is more common than white down and is sometimes regarded as less desirable because it may sometimes be seen through translucent or lightly coloured fabrics. However, colour has no bearing on the down’s thermal performance or cleanliness, and in the vast majority of products an end user will not even be aware of it.

    Most of the down that we buy is grey. However, in some products with lightweight and lightly-coloured shell or lining fabrics we pay an additional premium for white down. White down is permitted to contain a small percentage of grey down or ‘black spots’, as obtaining a completely pure white down naturally is not practicable. These black spots do not affect performance and the down functions identically whether it is white or dark. As down moves inside baffles the position or even appearance of these spots is only ever temporary. It is possible to buy pure white down where there are no black spots, but this down has undergone an additional processing stage where it is sorted by hand. As a result, its price is much higher and it is available only in limited quantities.

    Our down undergoes testing before it leaves our down supplier, once it reaches the garment or sleeping bag factory, and some final production garments are tested to ensure that the down meets the specification that we require.


    In 2009 Mountain Equipment became one of the first outdoor brands to introduce independent auditing of our down supply chain. Quietly introduced, without fanfare or press-releases, DOWN CODEX® set out to understand an industry and supply-chain that was largely ignored and certainly little understood.

    All products contain a code that can be entered into our DOWN CODEX® website to trace the down that they contain. Not only can you identify the source of your down but the audit relating to that source and the down batch test results can also be viewed.

    Outer Fabrics

    Outer face fabrics are a sleeping bag’s first line of defence against moisture, snow, and spilt drinks. They stop insulation escaping the sleeping bag, but also allow perspiration out, and are an important factor in comfort. The table below summarises our various outer fabrics’ performances, with further details given below:


      For extreme conditions, GORE-TEX INFINIUM™ will protect against exposure to moisture thanks to its durably light, exceptionally breathable and rain-resistant membrane. With an incredibly light 10 denier outer face fabric and protective PTFE membrane it weighs just 38g/m² yet will defend against snowfall, snow-melt and the effects of condensation; ensuring that down maintains its loft even in cold and damp conditions.

    • DRILITE® Xero

      Exceeding the impressive 1500 mm hydrostatic head of the original DRILITE® LOFT but with a staggering weight of only 28g/m², DRILITE® Loft Xero is a class-leading fabric for the most serious users: it’s amongst the lightest highly water resistant shell fabrics in the world. Ideal for Super Alpine climbing and the most lightweight expeditions where protection, pack size and weight are critical to success.

    • Plasma

      One of the lightest downproof fabrics on the planet. Perfect for alpinists and backpackers for whom weight is absolutely critical. Despite being just 26g/m², the fabric has exceptional tear resistance, giving you peace of mind on longer or more remote trips.

    • DRILITE® Loft 30

      Considerably lighter than the original DRILITE® Loft Fabric, but still with the same highly water resistant 1500 mm hydrostatic head, DRILITE® Loft 30 weighs 55g/m² and is the ideal fabric for sleeping bags destined for serious mountaineering, climbing, and backpacking in difficult conditions.

    • DRILITE® Loft 20

      One of the lightest versions of DRILITE® Loft available. Our 20 denier version weighs just 36g/m² yet still affords the same highly water resistant properties of the original with an impressive 1500mm hydrostatic head.

    • HELIUM™ 20

      Weighing just 38g/m², HELIUM™ 20 uses 20 denier yarns to create a fabric that is compressible, tough, and extremely comfortable. Its densely woven construction ensures the highest levels of downproofing, wind resistance and resistance to heat loss. The new HELIUM™ 20 offers greater handfeel over previous HELIUM™ fabrics as well as reduced seam slippage, resulting in even greater durability than the previous fabric.

    • HELIUM™ 40

      A durable and well-proven version of our Helium™ fabrics offers great all round long-term performance without adding undue cost. It’s easily cared for and offers excellent comfort. It is 53g/m².

    • Aiguille Noire de Peuterey.

    Sleeping Bag Fit

    It's worth getting a bag that fits you. One that is too tight and restrictive will be uncomfortable if used for any length of time, while one that is too big can feel cold as the air inside may circulate freely.

    Every Mountain Equipment Sleeping Bag is specified to one of five different fits: Expedition, Mountain, Alpine, Valley, and GT.

    In turn, our sleeping bags are available in either Regular or Long lengths, and our women’s specific shape and specification in certain models. Women’s sleeping bags are shorter than the equivalent men’s sleeping bag by 15 cm/6 inches and also offer a marginally smaller footbox to suit smaller feet. They also come with EXL® stitching at the midriff which provides greater comfort, warmth, and an improved fit.

    • Expedition Fit

      Wider and marginally longer than our Mountain Fit, the Expedition Fit caters for the needs of high altitude mountaineers and polar explorers who need to wear or store additional items of clothing or even their boots inside their sleeping bag.

    • Mountain Fit

      The foundation of all our fit blocks, this semi-tapered mummy profile combines excellent thermal efficiency and comfort for all-round mountain use.

    • Alpine Fit

      Slightly more tapered in the upper body and in the legs than our Mountain Fit this fit maximises thermal performance and minimises weight for the upmost performance.

    • Valley Fit

      Providing the greatest possible room and comfort. The hood of the bag will accommodate a full-size pillow, and the bag’s main body profile will easily accommodate relaxed postures whilst the enlarged foot box gives extra wiggle room.

    • GT ('Grand Tourer') Fit

      Our largest fit block, this is our Alpine fit but with every dimension increased by approximately 15%. It follows the same tapered shape as the Alpine fit but offers greater room for larger sleepers.


    • Aiguille Noire de Peuterey.


    How a sleeping bag is constructed makes a big difference to durability, its ability to maintain warmth in wet conditions, and its weight. We use more complex construction methods than any other brand, but we do this because on longer or extreme trips, it really matters. It is also key to ensuring even warmth throughout a sleeping bag, as there is no point in having a warm torso if your feet and head are freezing.

    Sleeping bag construction relates to how the insulation is held in place. For down sleeping bags that means how the baffles are constructed, and for synthetic sleeping bags it relates to how the sheets of insulation are sewn together.

    You can find out more about the baffle type or construction type for each of our sleeping bags on their product pages.

    • Aiguille Noire de Peuterey.

    Explore the range

    Trace your down

    What is the DOWN CODEX code?

    Click here to get a demo code and trace