Three things affect how warm you will be in a particular sleeping bag.

•    First is the environment: is it cold outside; what are you using for shelter; is there a breeze; what are you sleeping on?

•    Second is you: are you a hot or cold sleeper; is your metabolism fast or slow; do you sleep in the buff, rugged up or somewhere in-between; when did you last eat and drink? (And if you’re a woman, you will feel the cold more than a man: it’s not just a gender stereotype, it’s a fact.)

•    Both you and your environment make a huge difference to how warm you will be, and we can't control either of these things. The third factor is your sleeping bag.

All One Planet sleeping bags are temperature rated in accordance with EN 13537.

What is EN 13537?

‘EN 13537: 2002 Requirements for Sleeping Bags’ is the official European standard for the labelling of sleeping bags. It applies to all sleeping bags with the exception of those for extreme temperatures (comfort range below -25ºC) and sleeping bags used by the military. The standard was published in 2002 and has now been adopted in many countries.

•    ‘Comfort’ rating is based on a ‘standard’ woman having a comfortable night’s sleep.

•    ‘Limit of comfort’ is based on the lowest temperature at which a ‘standard’ man is deemed to be able to have a comfortable night’s sleep. This is the figure we use in our product descriptions.

•    ‘Extreme’ rating is a survival rating for a ‘standard’ woman. According to EN 13537, ‘a strong sensation of cold has to be expected and there is a risk of health damage due to hypothermia’. This is a survival rating only, and consumers should not rely on this rating for general use. The best guidelines are the comfort and limit of comfort ratings.

Comparing sleeping bags

Choosing a sleeping bag can be complicated as there isn’t a consistent, universally adopted method of rating the warmth of the bags. Many brands, including One Planet, have adopted EN 13537 as it is a reliable, scientific rating method. However, not all manufacturers have their bags tested to this standard, so care should be taken when comparing warmth claims across brands. Bags are also tested when new and clean, with bags needing regular cleaning to maintain performance.

For more information about EN 13537, please download this PDF document.

Temperature rating in accordance with EN 13537

Our sleeping bag range contains more than 60 models, not to mention the endless variations available in our custom-filled bags. It is impractical to test every model and size so, in accordance with the standard, we choose a cross-section of our range for testing, the results of which allow us to draw logical parallels to establish the performance of the rest of our sleeping bags. We continue to test new bags to increase our knowledge bank.

The tests are performed at the Kansas State University to standard EN 13537.