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The Ultimate Guide to Choosing a Sleeping Bag

September 06, 2016
The Ultimate Guide to Choosing a Sleeping Bag

There are few experiences more enjoyable than waking up after a great night’s sleep in the outdoors. Unfortunately for many campers, that’s a rare experience indeed.

But it really doesn't need to be – sometimes all you need is the right gear for the job. The combination of tent, mattress, and sleeping bag is tried-and-true, but if one piece of the puzzle doesn't fit quite right, it can drastically affect the overall performance of your shelter.

In this buyer's guide, we're going to focus on sleeping bags: we'll explain the many ways sleeping bag shape, season & temperature ratings, fill types, and additional features can affect the performance of a particular model.

So stick with us to learn everything you need to know before choosing a sleeping and get closer to that fabled, peaceful night’s sleep in the great outdoors.

a hooded sleeping bag provides extra insulation around the head on cold nights   how to choose a sleeping bag

Sleeping bags for all Australian seasons

There are so many different types of sleeping bags out there, how do you begin to go about choosing one? The first step is to ask yourself is how cold is it going to be the vast majority of the time I am camping?

Answering this question will help you determine the temperature range that you should be looking for in a bag.

You will notice if you look at a few sleeping bags online, that many manufacturers and websites like Outdoria, label their sleeping bags based on seasonality. This is a broad spectrum rating that gives you a rough idea of that bags warmth and best-use environment.

Sleeping bag season ratings are similar to those given to tents and look something like this:

  • One-season: The coolest bag on the spectrum; one-season bags are suitable for camping in late spring through summer. Bags that fall into this category often do away with features such as hoods and can be zipped all the way open, great for camping in hot, humid weather.

  • Two-season: More versatile than one-season bags, two-season sleeping bags are best suited to spring / summer, and some early autumn camping.

  • Three-season: Perhaps the most versatile of all sleeping bags, three-season bags are designed to keep you warm through spring, summer, and autumn, and can even handle warmer winter nights. Three-season bags are available in a wide range of shapes and fill types offering plenty of options for would-be buyers.

  • Four-season: Built to give you a great night’s sleep even when the mercury drops, a four-season bag is made for autumn and winter camping. Four-season bags usually feature hoods that encompass you head improving insulation on very cold nights. In Australia, you might find you spend the whole night with your four-season bag zipped open if camping in spring, summer, or autumn.

  • Five-season / expedition: The warmest of the lot, five-season sleeping bags are heavier, more durable, and often feature waterproof breathable outer fabrics to stop rain and snow soaking through in the night.

By now you should have a rough idea of the conditions you will most frequently experience while camping, and therefore, which season rating your new bag should fall under.

To get a more precise understanding of sleeping bag temperature ratings, however, we need to travel to Europe. Well, sort of.

EN 13537 - sleeping bag temperature ratings explained

Back in 2002, the European Committee for Standardization (CEN) created EN 13537, which today is the only industry standard for sleeping bag temperature ratings. EN 13537 gives manufacturers a series of standards on which to base their temperature rating tests in an attempt to help customers compare the capabilities of sleeping bag products across a range of manufacturers.

When you’re looking at a range of sleeping bags, be sure to look at each bag’s temperature rating to get a much better idea of how it is likely to perform based on the outside temperature.

But bear in mind, EN13537 is a standard based on 'standard models' for humans. It's important to remember that sleeping bag warmth is subjective on account of the fact that everyone’s biology is different. When CEN established the standards – upper limit, comfort, lower limit, and extreme – they used thermal mannequins configured based on average male and female physiology. Unfortunately for most of us blokes, we're not all 25, 1.73m tall, and weigh 73kg. And not all women are 25, 1.60m tall, and weigh 60kg either.

So while a sleeping bag’s temperature rating is very useful when choosing a bag, like seasonality, it is just a guideline. More importantly, you need to consider the conditions you will be camping in most frequently, the quality of your tent, and how warm you usually get when you sleep.

Some experts suggest that you should always choose a bag with a higher temperature rating than you think you will need. It’s true, you can always zip your bag open. But remember we live in Australia: unless you’re going camping in Tassie in winter or you're looking for a bag suitable for camping above the cloud line, a bag with a 'comfort' rating of -5°C is probably unnecessary.

Read More: Australia: a camper's wonderland

So what does the temperature rating on that bag you like actually mean?

Firstly, it should give you a 'comfort' rating in degrees celsius. This tells you the outside temperature at which that bag will keep a ‘standard man’ or ‘standard woman’ sleeping at ease throughout the night. 'Comfort' is basically defined as lying in a relaxed position with the bag zipped closed, without sweating or feeling like you need to cuddle your mate Jim for extra warmth.

The manufacturer will also give you an idea of the limits of that bag. Some bags will provide an ‘upper limit’ (the outside temp at which you’ll be sweating buckets in this bag), while others will simply list the 'lower limit' and 'extreme limits' of the bag.

The ‘lower limit’ is the outside temp at which you’ll be rolling over to cuddle your mate Jim for extra warmth. The ‘extreme limit’ suggests the absolute top-end capabilities of that bag. At the extreme limit – say your bag is rated to -15°C – your sleeping bag is capable of keeping you alive, but if you spend any great length of time in those conditions your toes might turn blue and later fall off.

The infographic below compares the different sleeping bag shapes popular today, it shows you what temperature ratings often look like when listed on a sleeping bag's shell, and weighs up the pros and cons of down and synthetic fill materials. If you're not sure what some of those things mean, keep reading for more on bag shape, fill materials and additional sleeping bag features.


Just right click and save this infographic to refer to later. Please note: the grading system used to compare fill and bag shapes is for demonstration purposes only and is not based on any industry standard.

At this point, you might be wondering, how can one one sleeping bag be that much warmer than another? Now we need to talk about sleeping bag fill materials.

Natural down vs synthetic sleeping bag fill

Fill is the stuff that makes up the insulating layer that keeps your sleeping bag warm during the night. Fill material consists of either natural goose (or duck) down, or synthetic fibres.

Both have their pros and cons and are better at keeping a camper warm in different conditions. Let’s first take a look at natural down to learn how it works as an insulator and the pros and cons of choosing a down-filled sleeping bag over a synthetic-filled bag.

The low-down on...down

Down, of course, comes from birds. You’ve probably seen it on small chicks; it’s that super-soft fluffy plumage that they have before their big feathers come in. On older birds, down sits underneath their outer feathers keeping them warm.

Goose down is the most common natural fill material used in sleeping bags and outerwear. Down is gathered in a number of ways, some more ethical than others. Animals can be killed for their meat and for their down at the same time, minimising wastage. Alternatively, they are killed for their down alone or live-plucked which can be harmful – both physically and psychologically – to the animal.

But, it is possible to harvest goose down without killing animals. Geese naturally moult over time meaning their down can be gathered without causing unnecessary harm. Some companies such as Patagonia claim they harm no animals in the sourcing of down for fill materials.

What is 'fill power'?

When you’re browsing the range of down sleeping bags, you’ll notice that some are rated with a three digit number (for example, 500, 600, or 800+) and that those with higher ratings are often more expensive.

This number represents the sleeping bag's ‘fill power’ (or ‘loft power’) rating. In layman's terms, fill power is the quality of the down used in that sleeping bag. The fill used in bags with a higher fill power is much better at occupying space; that is, it will fluff up and occupy a greater volume than bags with a lower rating.

But don't get fill power confused with temperature ratings. Fill power is more useful when determining how warm a sleeping bag is pound-for-pound. Higher quality down has a higher volume when fully lofted, therefore, sleeping bag manufacturers can use less fill to achieve the same temperature rating as a heavier bag.

Just be careful as some manufacturers list the quantity (weight) of down in the product name and only detail the quality (fill power) of the down in the description. For example, the Mont Helium 600 is actually a sleeping bag with 600g of 800+ down.

down sleeping bags are more effective at keeping your warm than a synthetic sleeping bag   how to choose a sleeping bag

Why choose down over synthetic fill?

So why do manufacturers use down at all if synthetic materials are available? To answer that question, we need to learn more about the way that fill materials behave under different conditions.

Goose-down feathers are made up of tiny little fibres that create pockets of air when bundled together. Your body radiates heat while you sleep; that heat is captured in those tiny air pockets and stays there, helping to keep your snug in your sleeping bag.

Those pockets are also very good at collapsing in on each other when you pack your sleeping bag away. This means down-filled bags usually pack down much tighter than synthetic bags, taking up less space in your pack.

It’s tough to recreate this with synthetic fibres. Manufacturers are working to create a synthetic fill that has insulating properties to match down, but so far, down is the ultimate insulator when it comes to sleeping bag fill materials.

Down might be warmer under regular conditions, but it’s not without its drawbacks. For one, down-filled sleeping bags don't retain heat as well as synthetic bags when wet and take longer to dry out the next day. They are also much more difficult to clean and are typically more expensive than a comparable synthetic model.

However, if you look after a down sleeping bag, you will likely get many more years of use out of it than a synthetic model.

How do synthetic sleeping bags stack up?

Synthetic fill sleeping bags have come a long way over the past few years, and will only continue to improve as synthetic fill technology is refined. After all, geese haven’t changed the way they create down for quite a long time – it just so happens they got the formula right, first time around.

Synthetic fill also varies in quality and weight, usually expressed in grammes on the bag’s description. The heavier the fill, the warmer the bag is going to be.

As we mentioned earlier, synthetic-fill bags have some advantages over their more expensive down-filled counterparts. Synthetic bags perform much better when wet: they don’t retain water as readily as down-filled bags, and therefore are not as heavy when wet. They are also much easier to dry, and clean after use. Manufacturers are also working hard to fortify synthetic fibres with water repellant compounds to greatly improve their effectiveness.

When you take all of that into account, a synthetic-fill sleeping bag is a very reasonable option when you consider the range of conditions you might experience while camping in Australia.

Sleeping bag size and shape

The shape of your sleeping bag will also greatly impact its ability to keep you warm. You will also likely discover that a sleeping bag's shape is directly related to its season rating. For example, more comfortable rectangle-shaped bags are usually one or two-season bags.

Rectangle sleeping bags afford the most room making them a great choice for campers who move around a lot in their sleep. They are ideal for spring and summer car camping as they are usually heavier than other bag shapes. Rectangle bags do not usually feature a hood and can be zipped open rectangle sleeping bag to form a makeshift doona on warmer nights.

Mummy bags get their name (you guessed it) from their characteristic mummy shape. Narrowing at the foot box reduces overall mass making them the go-to option for backpacking and hiking-camping expeditions. Mummy bags feature a hood that can be drawn tight, improving their ability to retain heat throughout the night and sometimes feature DWR (durable water repellent) shell coatings for additional protection against condensation and wet weather.

Tapered sleeping bags are the perfect midpoint between the more extreme mummy bag and the rectangle bag. Like mummy bags they narrow at the foot box to cut down on mass but afford more room to move around. Tapered bags are available in both hooded and hoodless variations.

rectangle sleeping bags are more comfortable than tapered or mummy sleeping bags

Rectangle sleeping bags are more comfortable and cooler than the other bag shapes, great for Aussie summer camping.

Womens specific bags vs mens and kids sleeping bags

Men usually sleep one to two degrees warmer than women at night, so it's really important to make sure that your sleeping bag is not only the right shape and temperature rating but that it is meant for you!

Women's sleeping bags are rated higher (for colder temperatures) than men's bags and often feature additional insulation around the feet and core areas. The same applies to kid's sleeping bags. Make sure that you not only consider the shape of your sleeping bag but who is going to be using it, and therefore, how big that bag needs to be.

It’s is possible to find sleeping bags of all different shapes and sizes with different temperature ratings. There is no one-size fits all, so make sure you read all product descriptions carefully and try a range of products to guarantee a good fit.

Sleeping bag features and optional extras

Once you’ve got a good idea what temperature rating, shape, and fill type you're after you can start to consider some of the key features and cool extras available with some sleeping bag models.

  • Shell and inner materials: Does the sleeping bag feature a waterproof breathable shell layer? Some high-end bags feature DWR coated shells to prevent condensation, snow, and rain from gathering on the outer and soaking through.

  • Baffles: These are the compartments found on down sleeping bags that keep the fill in place. They are arranged in panels vertically or horizontally and in some cases allow you to rearrange fill as desired. Have a look at the baffles on different bags to work out which one is best for you.

  • Hoods: Do you need a hood with you sleeping bag? Hoods are essential if you plan on going camping in very cold weather. If you can, try your sleeping bag on and check how the hood feels; you want to make sure that it is comfortable even when drawn tight.

  • Zippers: Does the bag fully open, or does the zip only open the bag part-way? Some expedition bags have very small zips that just allow you to get in and out of the bag whereas two-season bags usually open out like a blanket.

  • Foot box: this is the spot that holds your feet and keeps them warm. Pay attention to the construction of the foot box. Some manufacturers use durable / waterproof materials for foot box construction which is an added bonus.

  • Pockets: some sleeping bags have pockets for storing valuables close to hand. Internal are better than external because you don’t have to open your bag to get to them letting all that precious warm air out.

  • Stuff sack and storage sack: most sleeping bags come with a stuff / compression sack for storing your bag while on the go, and a larger storage sack for at home. If your sleeping bag is down-filled, make sure you only ever keep it in your storage sack at home because prolonged compression can degrade the down’s loft.

There really is nothing sweeter than waking up at first light, warm and comfortable, and deciding that it's quite alright to stay in bed for a few extra minutes before preparing for what the day might bring. Armed with new knowledge, we hope you feel confident searching for, choosing, and buying a sleeping bag that is the perfect fit for your outdoor lifestyle.

To shop a huge range of camping gear online from Aussie outdoor retailers, look no further than the Outdoria marketplace.