What do Sleeping Bag Season and Temperature ratings mean?

A sleeping bag could be one of your most important camping purchases, it has a major part to play in how much of a restful night you will get and your energy for the next day!  We’re here to help you understand what the gobbledegook means and how to pick the right sleeping bag for you.  However its worth pointing out that everyone sleeps differently, some are warm sleepers, and some sleep a bit cooler.  Also your tent, sleeping mat, even metabolism and  calorie intake will be factors that affect your body heat/

There are lots of things to consider when buying a sleeping bag, Synthetic vs Down, Shape, Weight, but perhaps the most important consideration is Temperature rating!  How warm will you be in your sleeping bag?

So what do Sleeping Bag Temperature ratings mean?

Temperature rating

There is a European Standard for Sleeping Bag Temperature Ratings EN13537.  Key to this rating is that it is now legal (in the EU) for sleeping bags to be labeled in a specific way.  The standard requires that manufacturers run a thermal manikin test on their sleeping bags to measure four temperature ratings (in degrees celsius).

  • Upper Limit — the temperature at which a standard man can sleep without excessive perspiration. It 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).

For the purposes of the manikin test a standard man is 25 years old, with a height of 1.73 m and a weight of 73 kg; and a standard woman is 25 years old, with a height of 1.60 m and a weight of 60 kg.

So with these temperatures you can pick the perfect bag for your expedition.  However for the more casual camper you may want a less technical guide to sleeping bags to find something that will be a good all rounder, that’s where seasons come in…


Seasons are a less technical rating system for bags, all sleeping bags must contain the above temperature ratings by law (in the EU) but for marketing or guidance the retailer may also use a season rating system.  As this isn’t regulated there may be different interpretations of seasons, and assumptions have been made into weather, type of person, tent etc.  The below is a generally accepted guide.

  • 1 Season - +5 - A One Season Sleeping bag is only good for Summer use.  It is comfortable in a temperature above +5 Degrees Celsius
  • 2 Season - 0 - A Two Season Sleeping bag is for Spring Summer Use, this will be comfortable right down to 0 Degrees.
  • 3 Season - -5 - The Three Season Sleeping bag is perhaps the most popular, comfortable to -5 Degrees it is a good all round sleeping bag choice which fits the needs of most campers.
  • 4 Winter - -10 - A Winter Sleeping bag will be comfortable as low as -10 degrees Celsius
  • 5 - Expedition - -15 - An Expedition Sleeping bag is used in extreme conditions, it is comfortable as low as -15 Degrees.

My Advice?  Use both these sets of information together.  Firstly think about when and where you are likely to camp and use your sleeping bag, this will give you a season guide.  Then you can identify from this the temperature specifications you need.  Just remember if you do go for a Winter bag / one with a low limit remember to check the comfort limit too, if it’s too low you may get very hot if you do a lot of Summer camping as well.  If this is the case consider a lighter sleeping bag and a fleece liner for the colder months.

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