How to Choose a Sleeping Bag

Should I get a down sleeping bag? A synthetic sleeping bag? What is the comfort rating? A sleeping bag can be a very expensive purchase, so it’s worth doing some research and finding out about the different brands, styles, and materials used. This article will explore the different options so that by the end you will  know everythign there is to know about sleeping bags. You can then have a read of the following areas:

Down Sleeping Bag Reviews

Down Sleeping Bag Comparison Chart

Synthetic Sleeping Bag Reviews, 

Synthetic Sleeping Bag Comparison Chart

The Age Old Question: Down vs Synthetic Sleeping Bags

Sleeping bags, Sleeping bag, Lightweight sleeping bag, Down sleeping bags, Mummy bags

The Cumulus Mysterious Traveller range of sleeping bags come with the inside and outside coated in Pertex. This is really useful as the interior can easily be cleaned by hand to remove any odours

Do you want a down filling or synthetic? Both have their merits. Synthetic sleeping bags are cheaper but take up more pack space and are roughly speaking, double the weight of a down sleeping bag with a similar temperature rating (more on this later). To date, nothing can beat the warmth to weight ratio of down.

However, down loses its insulative qualities when wet. Believe us when we say that nothing is more thankless than spending a night in a wet down sleeping bag! Manufacturers have got around this problem by producing down sleeping bags coated in Pertex which is a water resistent material that will resist a mild dew or condensation. Some of the higher end brands such as Crux’s Torpedo range have produced a sleeping bag that is coated in eVent fabric (a waterproof breathable fabric which you can learn about in our bivvy bag buying advice section).

Sleeping Bag Comfort Ratings

Choose sleeping bag, Lightweight sleeping bag, Down sleeping bag, Sleeping bags, Sleeping bag, comfort ratings, extreme temperature ratings

Every sleeping bag has a temperature rating. Often you will see an “Extreme Limit” but there’s no point looking at it. The figure will be impressive and is designed to seduce you into thinking the bag is incredible but in reality it’s fairly meaningless if you’re off on a normal camping trip. What’s important is the “comfort limit”. This is the lowest temperature at which a female can expect to remain comfortable whilst sleeping in the bag.

Shape of Sleeping bag:

Choose sleeping bag, Lightweight sleeping bag, Down sleeping bag, Sleeping bags, Sleeping bag

There are two styles of sleeping bags, rectangular ones and mummy shaped sacks. Mummy bags taper towards the feet and are more insulative than their rectangular counterparts as they effectively hug the body more. Most high end bags are designed like this. However there are things to consider when looking at mummy shaped bags. Make sure there’s enough room near the feet for you to move around. Some manufacturers make them rather tight so make sure you get in the sleeping bag and try it out!

Other Sleeping Bag Features and Things to Think About

If you’re going to be using the bag in cold conditions it’s worth looking for a few key features such as a hood with a draw cord above the chest to lock heat inside the bag. Some expensive ultra light bags forego a hood to make them lighter so it’s worth looking out for this. You should also look for a baffle that runs down the length of the zip as this will stop drafts getting in. I also like a big loop of material on the zip to make it easy to open and close but of course this is pretty simple to rig yourself.You should also consider that you’ll be using your sleeping bag in conjunction with some kind of mat, whether it be an air bed, roll mat or a self inflating mattress. It’s worth investing in a decent sleeping pad as it really makes a difference. This is most true when you look at ultra runner sleeping bags. Rab manufacture one of the lightest down bags on the market but it has barely any filling on the base. They assume it will be used in conjunction with a very good quality sleeping pad to mitigate this.

Choose sleeping bag, Lightweight sleeping bag, Down sleeping bag, Sleeping bags, Sleeping bag, baffle

It’s pretty obvious that you need to look after your sleeping bag as they can be extremely expensive. Loft is important as it gives you insulation. To help maintain loft it’s best to store your sleeping bag in a “loft sack”. These are massive bags that prevent your bag from being compressed. This is important for down bags but less so for synthetic ones. Another way to maintain the life of your sleeping bag and increase its thermal abilities is to use a sleeping bag liner. Sleeping bag liners are a great investment for a number of reasons. Firstly you can extend the warmth rating of your sleeping bag. Most people say that by using a liner you add a season. Secondly by using them you don’t need to wash your sleeping bag, just the liner, which is important as washing a down bag can be tricky! Finally on hot days in the summer you may find yourself just using a silk liner instead of a sleeping bag. Silk liners are lighter and more compact than cotton ones but they are about three times the price.

We’ve used a huge number of sleeping bags and mats so it’s impossible to recommend the ultimate one. You just need to think about how you’re going to be using and what temperatures you’re likely to face. We’ve compiled a comparison table to show you many of the bags on the market so you can see what appeals to you.


Here’s a brief guide to some of the materials/terms you might encounter in the manufacture and marketing of sleeping bags.

​Baffle: Chambers between the inner and outer lining of the sleeping bag containing the insulating material, either down or a synthetic product.  The different chambers prevent the insulation from all clumping together. Some high end bags such as those made by Crux have up to 48 baffles to prevent this problem and ensure the bag remains as thermally efficient as possible. There are various types of baffle, from vertical ones which run from the toe to the hood as favoured by some Marmot and Mountain Equipment bags, to bow wall and trapezoidal bow wall.

​Box Wall Baffle: probably the most common and simplest of the baffles. The chambers have vertical side walls to keep insulation together.  This design allows a uniform thickness of insulation throughout the sleeping bag,  improving the thermal performance compared to “stitch-through” construction. However there are cold spots down the walls. A better design would be Trapezoidal bow wall baffle or Shingle.

DriLite: Used by Mountain Equipment this is a waterproof fabric with a 7000mm hydrostatic head. It’s breathable and lightweight.

Drishell: ripstop nylon with an ultra light coating that achieves total wind block, high breathability and water resistance. Efficient given its overall weight. Favoured by PHD sleeping bags

​DWR: Durable Water Repellant care. Basically it is a water proof finish to a product that should allow it to remain breathable. The DWR achieves this in theory buy bonding to the fibres of the material and filling in the spaces between those fibres.

eVent: Waterproof breathable fabric mainly used by Rab in the manufacture of their clothing range. Crux use eVent in the development of their Torpedo series of sleeping bags.

Fill power: This is a way you can tell the quality of the down in your sleeping bag. A few grams of down are tested by compressing it under a stable temperature/humidity. If you had two sleeping bags of the same warmth rating, the one with the higher fill power will be lighter and pack down smaller. 450 is deemed to be of OK quality, 550 good, 650 –750 is considered very good, and 850+ is considered excellent.

​Mummy bag: This is an industry standard sleeping bag design. It incorporates a close fitting hood and from the shoulders to the toes the bag tapers. The tapering reduces the extra weight of carrying a bigger bag and is also more thermally efficient as you aren’t having to heat dead air space.

​Pertex Endurance: Incorporates an ultra-thin air permeable coating that is both highly breathable, water and wind resistant with a 1,000mm hydrostatic head. This layer protects the insulation material from the elements to maintain loft and retain warmth.

​Pertex Quantum: A silky ripstop nylon that shed slight rain and dries quickly. This is a material favoured by Rab and Haglofs.

​Primaloft: this is a synthetic insulation, an ultra-fine microfibre blend that is lightweight and water repellent. It also has a down like softness. Some ultra light sleeping bags will use a mixture of down and then primaloft on the underside of the bag.

Quallofil: synthetic material developed by Dupont for use in sleeping bags and parkas. Each filament has four longitudinal holes which trap air and add warmth. Quallofil is one of the best synthetic insulators.

Rectangular bag: These are much less thermally efficient than a mummy style bag. They are also heavier and bulkier but they tend to be the cheapest.

Ripstop: Tough, hard wearing nylon and polyester fabric woven into the material in a checkerboard or diamond pattern to prevent or reduce the threat of tearing.

Synthetic Insulation: Generally speaking this made from fine, hollow fibers. This reduces the bag’s weight and bulk while increasing loft and warmth. Synthetic insulation is also warm when it is wet, unlike down.

Trapezoidal box wall baffle: this is a type of baffle or chamber design used to keep the sleeping bags insulative material from clumping together. This is a very thermally efficient design that is warmer than standard box wall.

Shingle baffle: This is an advanced chamber design that delivers high loft, good thermal performance and excellent comfort for the user.When it comes to sleeping bags there are two major choices you need to consider. Do you want a down filling or synthetic? Both have their merits, for example synthetic is cheaper than down and it stays warm even when it gets wet, unlike down which loses its insulative qualities after a dunking in the river.  However Synthetic materials are often bulkier and heavier compared to down which is very light weight.

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