Choosing a Sleeping Bag

We all know how important it is to get a good night’s sleep, and never more so than after a long day in the mountains. So, whether you’re camping wild or simply enjoying the facilities of a well run campsite, a good quality sleeping bag will pay dividends in aiding recovery for the next day.
This guide will cover the following aspects of sleeping bag design:

1. Selecting the Correct Comfort Rating

2. EN Ratings

3. Construction

4. Shapes and Feature

Selecting the Correct Comfort Rating

Sleeping outside at altitude can entail much colder sleeping conditions than at lower levels, and so it is essential to choose a suitable sleeping bag for the worst-case scenario at your planned camping location, and by weather and temperature expectations. You may not require a four season Down bag for summer family camping in Cornwall, but it’s true that it’s easier to vent off in a higher rated sleeping bag (i.e. unzip), than trying to get warm in one that’s not rated highly enough. If in doubt, err on the side of caution and choose a warmer bag!

The comfort rating of a sleeping bag relates to the lowest temperature at which the bag will keep the average person warm and should be used only as a guide. The minimum recommended temperature relates to the lowest temperature recommended by the manufacturer, but beware, do not expect a restful nights sleep if using a bag at the extreme end of its temperature rating!

Thankfully, on Webtogs you can use the left-hand filters in the sleeping bag category to display bags according to their comfort rating (see the next section for explanation of this term). However, we are aware that not all manufacturers and suppliers give you this option. Another commonly used sleeping bag classification system is the ‘season’ rating, which works as follows:

•    1 Season Bag     – Comfortable down to 10 °C

•    1-2 Season Bag  – Comfortable down to 5 °C

•    2 Season Bag     – Comfortable down to 1 °C

•    2-3 Season Bag  – Comfortable down to – 2 °C

•    3 Season Bag     – Comfortable down to – 5 °C

•    4 Season Bag     – Comfortable down to – 7 °C

EN 13537 Ratings

Sleeping bags sold in the EU containing less than 800 grams of down, should now clearly display the standard EN Ratings for temperature. As with all things bureaucratic, this rating system is not always the easiest to understand, but it does provide a standard measure of temperature across different types and brands of sleeping bag. The EU testers identified that women generally retain less heat than men at a given temperature, and thus feel the cold more. With this in mind they came up with 3 distinct temperature ratings:

•    Comfort – The lowest temperature at which a typical woman will have an uninterrupted night’s sleep.

•    Comfort Limit – The lowest temperature at which a typical man will have an uninterrupted night’s sleep.

•    Extreme – A survival rating only. It shows the lowest temperature at which a typical woman would avoid hypothermia.

The Comfort, Comfort Limit and Extreme EN ratings will be displayed in the following format on Webtogs, if the bag concerned has been EN tested:

Minimum temperature icon

The most important point to make here is the EN Extreme rating is NOT a suitable rating to base your choice of sleeping bag on, as to do so can be highly dangerous. Remember, if in doubt; opt for a sleeping bag warmer than your needs. With this in mind, Webtogs always display the manufacturer’s minimum temperature rating for each bag beneath its product Image. It will appear alongside the other important sleeping bag features; weight and packed size, as demonstrated on in the graphic to the right.

Other Factors that Affect Comfort:

•    Sleeping Mat: Invaluable item, designed to insulate the user from the ground and offer a greater degree of cushioning.

•    Tent: The air trapped in your tent will be warmer depending on how well it is insulated and draught free. Also, the smaller the tent, the warmer the tent will be.

•    Metabolism: We’re all individuals, and our bodies react differently at night. Some people are ‘cold sleepers’ and wrap up well, while others can be ‘warm sleepers’ and prefer to have some space to kick off the covers.

•    Clothing: Sleeping bag comfort rating is gauged under the assumption that a sleeper wears base layers on top and bottom, and what you wear can greatly affect your temperature. Ensure that you wear only dry, clean(ish) base layers!

•    Gender: Women on average are colder sleepers than men and will benefit from using a warmer sleeping bag.

•    Hats and Hoods: A great deal of heat is generated and lost through an unprotected head. Close the hood of the sleeping bag around your head for added insulation, or wear a hat.

•    Hydration: Keeping yourself fully hydrated during the day will help towards a good nights sleep, as will a hot drink just before bed – just keep your torch and slippers handy!

•    Sleeping Bag Liner: This is a great way to upgrade the warmth factor of your bag and keep the bag clean too. Silk liners are lightweight and effective, fleece is the warmest but bulky, and cotton liners are an excellent cheap compromise.

Sleeping Bag Construction

A sleeping bag is designed to keep you warm by trapping non-circulating air between your body and the bag. Your body warms the trapped air inside and the higher the level of insulation, the warmer you will be. The less empty space there is to heat between yourself and the inside of the bag (the tighter the fit) the quicker you will warm up, and the warmer you’ll stay


Sleeping bag insulation falls into one of two categories; down or synthetic, and each system has its own advantages and disadvantages, summed up as follows:

Down: A quality down bag is the lightweight sleeping system of choice for Mountaineers, serious backpackers and most certainly for those who count the grams such as expedition cyclists, for whom warmth-to-weight ratio is paramount. The weight and warmth of a down bag depends upon the quantity of down inside it, and most importantly on the fill power of the down, which can be anything from 600 to 850+. A higher fill power means greater warmth per gram of down, so whether you’re looking for an ultra-light sleeping bag for mild climates, or a 4-season bag for cold weather warmth; the higher the fill power the better! Although a quality down bag will be constructed with a durable water repellent outer fabric (DWR), this will not be waterproof, and a down bag will bunch-up and loose it’s insulating qualities rapidly when wet, as well as take ages to dry. Before climbing into your down bag for the night, you should lay the bag out, puff it up, and allow a few minutes for the down to do its work and trap the air. Lightweight, compressible and comfortable, a down bag should be treated with respect and care. For more care information, visit the Down Care Gear Guru page.

Synthetic: Modern synthetic sleeping bags are more durable than down bags in real-world conditions, and are excellent for family camping. Through modern technology, quality synthetic sleeping bags have had their bulk and weight greatly reduced to become viable alternatives to down when buying on a budget. As with a down bag, a quality synthetic sleeping bag will be constructed using a DWR coating, which helps to protect the bag, but will not keep it waterproof. The good news is that a synthetic bag will retain the majority of its insulating qualities when wet, and will dry quickly compared to a down bag.


Outer shell construction of a quality sleeping bag is typically constructed from Ripstop nylon or polyester for durability, and will have a Durable Water Repellent (DWR) coating to help protect the insulation from moisture ingress. A DWR coating is not used in the lining of the bag, so as to enable moisture from perspiration to pass through the bag, moderating body temperature.

Sleeping Bag Shapes and Features

The most common shapes for sleeping bags are mummy or rectangular and are constructed that way for different reasons. Here’s an explanation of the two styles:


Following the natural shape of the body, a mummy shaped bag will be wider at the top to accommodate the shoulders, tapering sharply towards the feet and into a box shaped foot section. Contouring the body vastly reduces the amount of dead air trapped between you and the bag, and is the most efficient way of keeping you warm. Women are well catered for here, where many manufacturers produce a women’s shaped bag: narrower at the shoulders and wider in the mid (hip) area and have extra insulation in the foot box and upper body sections. For some people, a mummy bag can feel a little claustrophobic so its worth trying one out first, but that said, if you are venturing out high into the wilds or cold climes, then a mummy bag should be seriously considered. Look out for internal storage compartments near the shoulder areas in more extreme designs, to stash and keep your socks or drink bottles warm and unfrozen. With many bags you will also get a small external pocket.


These basic sleeping bags are cut to the same width from the shoulders down to the feet, thus giving you plenty of room to move around. The negative is that they tend to be much less effective at keeping you warm in cooler temperatures. On the plus side, rectangular bags do often have the added ability to zip together to form a large blanket if their zippers are compatible. Rectangular bags are ideal for low level family camping and when weight, bulk and transport is less of an issue.

Sleeping Bag Weight

Bag weight is a vital statistic to consider if you’re planning on carrying a sleeping bag in your pack for a significant distance, whether you’re hiking, cycle touring, or mountaineering. As covered earlier, down is the lightest insulation material for use in sleeping bags, so is ideal for weight-sensitive pursuits. The higher the fill power of a down bag, the warmer it will be for it’s weight and the more expensive it’s likely to be. Where possible you should aim to strike the ideal balance between light weight and budget, though never at the expense of warmth. On Webtogs, we include a weight graphic with every sleeping bag, alongside its product image, so you can compare a range of different bags at a glance. It will appear alongside the other important sleeping bag features, comfort rating and packed size, as in the righthand image.

Sleeping Bag Packed Size

Packed size is another important factor to take into account if you’re planning on carrying everything you need for a multi-day trip in your pack. A bag with small packed size frees up space for additional clothing layers, provisions or luxuries, as well as reducing the need for a larger pack and improving weight distribution. All this can add up to a far safer and more enjoyable experience. As with comfort rating and weight, Webtogs include packed size graphic with every sleeping bag, alongside its product image, so you can compare a range of different bags at a glance. It will appear as in the image on the right.