Sleeping bags are one of the only products on the market that have a temperature rating. Think about it, you don’t buy a jacket with a temperature rating, or even a quilt for your bed at home.
If you’re feeling cold you put on an extra jumper or extra blanket on the bed. Despite this, we expect that a sleeping bag with a ‘temperature rating’ of 0 degrees will keep us toasty warm in the snow no matter what type of person we are.
The reality is that this temperature rating really is just a guide. We all feel the cold differently so we simply cannot expect a sleeping bag to be such an exact science, or that one temperature rating fits all. So, what does temperature rating mean? And, how can we use this roughly equated number to help us choose an appropriate bag for the job?
Think about the conditions where you’re planning on using your bag and if you’re generally a cold sleeper before you make your decision. Image: Sea to Summit
What temperature sleeping bag do I need?
Firstly, before delving in – you should ask yourself:
- Do you mainly go away when it’s cold? When it’s hot? Or both?
- If it’s going to be cold, how cold will it be? Is there a chance of frost or snow?
- Are you sleeping outside? In a tent? How big is the tent? Or maybe it’s just for sleepovers?
With those considerations in mind, let’s talk sleeping bag ratings.
+5 to +10 degree sleeping bag
A +5 to +10 is considered a summer bag. It is roughly as warm as sleeping with a sheet or light blanket over you on your bed at home.
0-degree sleeping bag
A 0 degree bag is a great all-rounder but won’t keep you warm in the snow or frosty night – it’s about the same as having a regular doona on your bed at home.
-5 to -10 degree sleeping bag
A -5 to -10 degree bag is considered a winter bag for typical Australian climates – it should be similar to having flannelette sheets and an extra blanket or 2 on your bed at home.
Top tips to help you choose the right temperature bag:
- Choose a bag that is roughly 10 degrees lower than the ambient temperature you will be sleeping in (e.g. if it’s getting down to +5 degrees overnight, get a -5 degree bag).
- Remember, the temperature rating is the temperature that will wake you up! For a lot of us, we will wake up as we get closer and closer to that rated temperature.
- A 0-degree bag does not mean that at +1 degree you’re warm, and at -1 degree you’re suddenly cold.
- Lastly, remember we all sleep differently. Women and children generally sleep colder than blokes, and we all come in different shapes and sizes with different levels of our own insulation!
These are all factors you’ll need to consider to help you select the right bag. If you want to understand how temperature rating is tested and measured, then read on.
Look out for sleeping bags that are marked with EN13537 – as that indicates they’ve been tested to an EU standard. Image: Sea to Summit
What does the temperature rating mean?
Let’s use a 0 (zero) degree rating as an example: A sleeping bag that is rated to 0 degrees means that at 0 degrees anyone using this bag, no matter how warm they sleep, will be cold, awake and uncomfortable.
How do we arrive at this sleeping bag rating?
Sleeping bags have to be independently tested by the manufacturer to obtain the rating. The rating is often based on an R-value which is a measurement of insulation – just like the insulation in the walls of your house.
Some manufacturers will do real world testing on one sample of their insulation, and apply a formula to the different sleeping bags, whereas sleeping bags tested to an EN (European) Standard are the most accurately tested bags.
What is the EN Standard?
There are no testing guidelines here in Australia, so look out for bags that have been tested according to EN Standards. The EN Standard for sleeping bags is marked EN13537. The standard measures 4 temperature ratings:
Upper Limit – the temperature at which a standard man can sleep without excessive perspiration. This is established with the hood and zippers open and with the arms outside of the bag.
Comfort – the temperature at which a standard woman can expect to sleep comfortably in a relaxed position.
Lower Limit – the temperature at which a standard man can sleep for eight hours in a curled position without waking.
Extreme – the minimum temperature at which a standard woman can remain for six hours without risk of death from hypothermia (though frostbite is still possible).
Note: Not all manufacturers will list all 4 ratings.
For example, Sea to Summit sleeping bags are all tested to EN Standards. Image: Sea to Summit
At the end of the day, no amount of laboratory testing is going to be 100% accurate for you. Cheaper sleeping bags will advertise a more generous rating that may not be accurate. Bags that list the EN Standards will be more accurate. But as that process is expensive, it will affect the price tag.
If you want some advice on how to make your sleeping bag warmer in the winter months, then check out our guide here.
The last tip I’ll leave you with for selecting a temperature rating is: you can always shed a layer or unzip your bag if you’re hot, but if you wake up freezing cold in the middle of the night there won’t be much you can do to get warm!
What bag do you have and what rating do you find to be most versatile?
About the writer...