Buying a Sleeping Bag is a big and sometimes daunting process.

What goes into all our designs is an uncompromising and painstaking approach to achieving warmth and comfort, baffle by baffle. A poorly designed Sleeping Bag is not only frustrating to use it can also, in the extreme, be life endangering.

We have developed answers to all the difficult questions that get asked when sleeping bags are put to the test.

This sleeping bag buying guide is designed to help you navigate the sometimes tricky decisions involved in buying a Sleeping Bag. In this guide we’ll cover everything from temperature ratings and weight, the difference between Down and Synthetic insulation, to our specific fits and Sleeping Bag ranges.

Which ratings mean the most to you?

Temperature ratings are one of the most important factors to consider when purchasing a Sleeping Bag. Whilst you don’t want an uncomfortably cold night’s sleep, you equally want to avoid being too warm or carrying a Sleeping Bag too heavy for your trip.

There are various methods that help to determine the temperature ratings for a Sleeping Bag. However the European (EN) standard, known as EN 13537/ISO 23537, has now been adopted by the majority of Sleeping Bag manufactures, including Mountain Equipment.

The test takes place in an environmental chamber at fixed temperature. A heated manikin is placed inside the Sleeping Bag, and the Sleeping Bag rests on a specific foam mat. The manikin wears a thin base layer that’s typical for people to sleep in. Using a controlled environment and manikin reduces the risks and logistical complications of field testing on real people.

While we use the EN13537 / ISO23537 test to help inform the design and engineering of our Sleeping Bags, it is neither perfect nor relevant for all Sleeping Bags. Bags designed for extreme conditions are exempt, for example.

As such, whilst we quote EN13537 / ISO23537 results for the vast majority of our Sleeping Bags, for some specialist Bags (especially those which utilise very light, air permeable fabrics) the standard is a poor indicator of real-life thermal performance. Some of the factors to consider in relying on the EN13537 test Standard include…

Manikin Shape: The manikin used in the test is a specific shape, and if it compresses any part of the insulation around it then the Sleeping Bag performs poorly. The same effect would occur if a larger person attempted to use a Sleeping Bag that was too small for them. As a result our more tapered Alpine Fit bags sometimes have EN13537 / ISO23537 results that are slightly lower than the equivalent Mountain fit bag, even though for many users these bags will actually be more thermally efficient and consequently warmer.

Face Fabrics: When sleeping inside the shelter of a hut or tent the face fabric of a dry Sleeping Bag barely affects its warmth. This is because in these conditions there is very little air flow over the Sleeping Bag. However, the EN13537 / ISO23537 test is carried out with air moving at 0.3 m/s (about 1 mph) directly downwards onto the Sleeping Bag. This air movement is faster than users experience in most conditions, and is in a different direction. Thus, if a Sleeping Bag’s face fabric is air permeable (lets air through) then in the test it will tend to produce relatively poor results. For this reason, bags such as our Fireflash, Firelite, and Firefly Sleeping Bags perform much better than their EN13537 / ISO23537 ratings suggest unless used in very drafty situations.

All of our Sleeping Bags display EN13537 / ISO23537 temperature ratings except our very warmest Sleeping Bags, our Extreme Expedition Sleeping Bags and Glacier Expedition model, which fall outside the range of the test.

The EN/ISO tests produce three different temperature ratings:

For some, minimum weight and pack size are essential.

Be honest: do you tend to car camp, backpack, or use your Sleeping Bag on alpine bivvy ledges? Depending on your usage, the weight and pack size of your Sleeping Bag may greatly differ in importance. If you are mostly going to camp in places where the pack size and weight are not an issue, then consider buying a bigger, more spacious Sleeping Bag.

However, if you are alpine climbing or backpacking and carrying your Sleeping Bag for an extended period of time, then a lightweight Sleeping Bag is really important. Look for a Sleeping Bag under a kilo (2.2lbs) for a Summer Sleeping Bag, 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 climates, 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!

If you intend on carrying your Sleeping Bag for long amounts of time, but have only ever used a Synthetic Sleeping Bag, consider switching to a Down Sleeping Bag.

But once you’re back from your trip, always make sure to store your Down Sleeping Bag in its storage cube, which we also provide, to ensure your Down maintains its loft. With Synthetic, it’s not quite so important, but it’s best to store a Synthetic Sleeping Bag uncompressed too.

What fill is best for your needs?

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, Synthetic is the way to go.

Our outer fabrics serve different purposes.

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

It’s worth getting a bag that fits well.

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 then available in either our standard regular or long sizes, and our Women’s Specific shape and specification in some 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 (but with increased fill weight). They also come with EXL™ stitching at the midriff which provides greater comfort, warmth, and improved fit.

It’s worth getting a bag that fits well – 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 them may circulate freely.

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.

Construction is key to long-term performance.

How a Sleeping Bag is constructed makes a big difference to durability, its ability to maintain warmth in wet conditions, and how much the Sleeping Bag weighs. We use more complex constructions than any other Down Sleeping Bag manufacturer, 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 and arranged in a Sleeping Bag. 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 page.

Goose Down Sleeping Bags

Our Goose Down Sleeping Bags are our most exceptional Sleeping Bags, designed for users who want to push their limits or for those who simply want one of the best Sleeping Bags ever made. We make three different ranges of Goose Down Sleeping Bag.

Duck Down Sleeping Bags

Our Duck Down Sleeping Bags offer similar performance to our Goose Down Sleeping Bags but at a fraction of the cost. They are a great choice for all but the most discerning of customers. We make four different ranges of Duck Down Sleeping Bags.

*Unavailable in USA

Recycled Down Sleeping Bags

Recycled down offers almost all the performance of virgin down but with less environmental impact. A superb option for all but high performance users.

*Unavailable in USA


Recycled down, recycled fabrics; the Earthrise is our most sustainable range of sleeping bags which will give you years of excellent service. Based on the design of our best-selling Helium models, Earthrise bags are high performance products that boast both serious warmth and outstanding green credentials.

Synthetic Sleeping Bags

Synthetic Sleeping Bags excel when you need totally reliable protection whatever the elements throw at you. Versus Down they are easier to care for and are usually cheaper. We make four different ranges of Synthetic Sleeping bag.


The warmest Synthetic Sleeping Bags we have ever produced, Auroras are winter and expedition bags par excellence. Highly protective, very warm, and designed for the harshest conditions and environments, Auroras utilise the very finest POLARLOFT® insulations and DRILITE® Loft fabrics to provide a range of bags that will thrive whether crossing Greenland or big walling in the Arctic.