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Photo Credit: Klaus Kranebitter/Marmot

How To Choose A Sleeping Bag

Choosing the perfect sleeping bag can spell the difference between success and failure for any camping trip. The choices are many; do you go for down-filled or synthetic? Two season or three? This guide will take you through everything you need to know about sleeping bags so you can choose the best one for you.

Sleeping Bag Seasons & Temperature Ratings Explained

The first thing to think about when buying a sleeping bag is 'when and where am I going to use it?'

It may sound obvious but the warmth requirements of a summer-only sleeping bag are going to be very different to a bag that you use year round.

For each sleeping bag, we include the comfort, limit and extreme temperature rating. These are results gained from testing under the EN-ISO 23537 ‘Requirements for Sleeping Bags’ Standard. The standard enables reliable comparison between the different brands and bags. The test produces three temperature results, which relate to different user experiences:

temperature guide

Comfort Temperature – based on a ‘standard’ adult woman having a comfortable night’s sleep.

Limit Temperature – based on the lowest temperature at which a ‘standard’ adult male is deemed to be able to have a comfortable night’s sleep.

Extreme Temperature – a survival only rating for a ‘standard’ adult woman. At this temperature, there is a serious risk of hypothermia and other temperature related ailments.

The temperature rating icon can be found on the features tab on each sleeping bag.

The two ratings that you should focus on are the Comfort Temperature and the Limit Temperature. For colder sleepers, the Comfort temperature is a good guideline. If you sleep warmer or are more experienced sleeping outdoors, the Limit temperature is likely to be more relevant. You want to make sure that these represent the lowest temperatures that you expect to experience.

NB: The EN-ISO 23537 standard is not accurate for sleeping bags at the extreme ends of the weight and temperature spectrums. For these bags, the ratings supplied are based on the manufacturer’s recommended sleep limit.

To make it easier to distinguish what and when a sleeping bag has been designed for we include a Season Rating. The ratings give you a clear indication of a sleeping bag's intended use and are split into six categories:

One season – these bags are ideal for UK summer use or travelling in warmer climates. Globe-trotters will appreciate their small pack sizes but closer to home they make excellent campsite bedding.

Two season – perfect for the late spring to early autumn temperatures experienced in the UK. As soon as the weather starts to improve these sleeping bags will let you get out and enjoy the summer outdoors, from surfing trips in Cornwall to walking holidays in the Lake District.

Three season – these sleeping bags cope admirably with early spring to late autumn UK temperatures. They will suit the more determined outdoor enthusiast who gets out as soon as the worst of the winter weather subsides and may stay out late into the year.

Three+ season – suitable for year round use in the UK, provided a sheltered off-the-mountain site has been selected during harsh winter conditions. This series of bags is aimed at serious outdoor enthusiasts from hikers and climbers to adventure travellers.

Four season – these sleeping bags have been designed for winter trekking and climbing, but are not suitable for high altitude mountaineering. They feature the highest quality components and superior materials to keep you warm and protected when the weather starts to hurt.

Four+ season – these bags are for extreme high altitude mountaineering and use in the world's harshest environments - think 8000 metre peaks and polar expeditions. Down-filled, they provide exceptional warmth to weight ratios and are often shaped to accommodate down clothing layers underneath for extra comfort.

Anatomy of a Sleeping Bag

Along with the temperature and season ratings, the features, insulation and material of a sleeping bag can all affect your comfort. Here are some of the things to look out for when choosing a bag:

sleeping bag diagramsleeping bag diagram
  • Hood – If you are a cold sleeper or heading somewhere where temperatures are likely to drop, a good hood is essential. Look for a hood that is fully adjustable and seals well around the face. The best fits tend to come from hoods made with multiple contoured baffles.
  • Neck baffle – Also known as a draught excluder or shoulder baffle. Effectively an extra tube of insulation sewn into the neck area, it creates a barrier of warmth around your neck and shoulders that stops heat from escaping/cold getting in.
  • Zip baffle – Similar to the neck baffle, it's an internal tube/flap of insulation that covers the zip to prevent heat escaping.
  • Zip – Sleeping bag zips can be full, three-quarter and half length. The latter save weight and require less stitching while the former are easier to use and better for venting. Two-way zips are particularly useful as you can vent from both the top and bottom of your bag for personalised climate control.
  • Shell material – The shell of a sleeping bag can range from being ultralight and highly compressible to heavier and more durable – the material usually corresponds to the activity it's been designed for. In damp or humid environments, a shell with a Durable Water Repellent (DWR) treatment is a bonus.
  • Insulation – There are two main choices when it comes to insulation: down or synthetic. Down is light, has excellent warmth to weight ratio and is very compressible, synthetic is better in damp conditions and is generally cheaper.
  • Foot box - Often you will see trapezoidal or comfort foot boxes mentioned in the sleeping bag specs. These allow you to lie with your feet in a natural position, with enough room for them to point ‘up' for better comfort (something walkers with weary feet may appreciate!).
  • Length - Sleeping bag lengths inevitably vary between brands and styles, so if you're particularly tall look out for the long versions available. A sleeping bag should fit over you comfortably, if you point your toes and the hood comes off then it's worth switching to something longer!

Sleeping Bag Shape & Fit


These bags are wider at the shoulders and narrower towards the toes, for an optimal balance between warmth, weight and comfort. The shape removes excess bulk but still allows the shoulders to lie flat. Expedition bags also follow the tapered design but are often oversized to accommodate down clothing layers inside, ideal when maximum warmth is required.

mummy sleeping bag shapemummy sleeping bag shape


Rectangular sleeping bags are roomier and allow a relaxed sleeping position, but aren't as efficient at keeping you warm. Great for summer festivals, car camping and sleepovers where their bulkier size doesn't matter, they can often be unzipped to lie flat for use like a duvet.

rectangular sleeping bagrectangular sleeping bag


It's not just a change in colour that differentiates a female specific sleeping bag from a male's. Women have been found to sleep colder than men, so women's sleeping bags usually have extra insulation built into the areas of increased heat loss – typically around the hips and in the foot box. They are also shorter in length and narrower in the shoulders to reduce excess bulk, weight and unnecessary heat loss.

female symbolfemale symbol

Types of Insulation

Deciding on the insulation of your sleeping bag is arguably one of the most important decisions you'll need to make. Sleeping bags are filled with either down or synthetic insulation; both have their pros and cons and will affect the performance, weight and price tag of the sleeping bag.


Ounce for ounce nothing insulates as effectively as down. Down filled bags are very light, warm and compressible, and when cared for correctly will last for many years. Down is measured in fill power, it represents how much loft the down has (i.e. how much space it can fill and insulate). Usually the higher the fill power the warmer the bag will be, although this also depends on the amount of down used too: 300g of 600 fill power will feel a lot warmer than 30g of 800 fill power down.

Pros - Light, warm, compressable

Cons - Susceptible to moisture*, expensive

*The exception being water resistant down. This is down that has a hydrophobic treatment for better water resistance and works better than untreated down in the damp UK climate.

down insulationdown insulation


Synthetic insulation retains a much higher percentage of its insulating properties when wet. It also tends to be easier to clean and comes with a more wallet-friendly price tag too.

Pros - Good water resistance, easier to care for, cheaper

Cons - Heavier and bulkier than down equivalent

synthetic insulationsynthetic insulation

So which one to choose? Ultimately it depends on your needs, the activity and how much you want to invest, but down-filled bags are better when weight and space is an issue while synthetics are great if you want good performance at a lower price. When it comes to kids, synthetic sleeping bags are often the most sensible choice thanks to their durable fabrics and easy-cleaning ability.

For a more detailed comparison of down versus synthetic insulation, look at our Insulated Clothing Buying Guide.

Sleeping Bag Construction

Although it's unlikely that you'll choose your sleeping bag based on construction, understanding the different techniques used to hold insulation in place is useful for knowing what kind of warmth and performance the bag can achieve. Without a barrier/baffle/seam line to hold the insulation in place everything would simply sink to the bottom of the bag leaving you with very warm feet and cold shoulders!

Below are the main construction techniques used to keep insulation in place:

Stitch Through

The shell and the inner liner are stitched directly together trapping the insulation between them. The downside is that it creates cold spots and allows heat to escape along the seam lines. Sleeping bags with a stitch-through construction are best suited to warm weather camping.

stitch through construction of a sleeping bagstitch through construction of a sleeping bag

Box Wall

A construction used for down sleeping bags. An internal baffle/wall sits vertically between the shell and the inner liner to stop the down from migrating, trapping it within boxes and removing the issue of cold spots. Box wall construction can vary between a simple box shape, a slanted shape or a trapezoidal shape to house the insulation, the latter is particularly popular as the down fills out the corners to reduce heat loss.

box wall constructionbox wall construction


A construction used for synthetic sleeping bags. Overlapping sheets of insulation are stitched to both the shell and lining, this keeps the insulation stable. Similar to the way roof tiles are placed, the overlapping reduces the chances of cold spots and heat escaping.

Shingle constructionShingle construction


Mountain Hardwear's Lamina construction used welding to hold the synthetic insulation in place. Welding eliminates the need for seams and avoids pinching, so the bags are light, warm and compressible and avoid the heat-loss problems associated with a stitch-through construction.

welded constructionwelded construction

Accessories & Care

So, after all that it's worth going back to where we started and mention warmth again. Pinpointing the seasons and temperatures you'll be using the bag in will go a long way in finding a sleeping bag that's suitable for you. However, it's important to think of your bag as part of a sleep-system as there are other elements that will affect your comfort too.

Sleeping mats – Even with a great sleeping bag you'll probably still feel the cold if you don't have a sleeping mat separating you and the floor. They vary as much as sleeping bags do in warmth and performance however they also have temperature ratings to make your decision easier. Choose the one that matches most closely to your needs and it should help you get that great night's sleep.

Sleeping bag liners - Usually made from silk or cotton, they are essentially a sheet bag that you use inside your sleeping bag. They add another layer of warmth, help keep your sleeping bag clean and in hot weather can even be used alone. If unpredictable weather is forecast they're a great way to add warmth to your bag without taking up too much room in your pack.

Storage care - Whether backpacking, climbing or camping, at some point it's likely you'll need to carry your sleeping bag, that's why all of the sleeping bags stocked at Ellis Brigham come supplied with a stuff sack. However, stuff sacks can greatly vary in dimension, compression ability and waterproofness. So if you've got a limited amount of space in your backpack or are heading out onto water it's worth double checking that the stuff sack works for your needs.

Once back home, many of the bags also come with a larger, looser storage sack which allows an airflow to your bag, it is especially important not to store a down-filled bag too tightly as it can damage the delicate contents inside.

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