EN 13537 (or EN13537) is a European standard designed to standardize the temperature ratings on sleeping bags manufactured and/or sold in Europe. As of January 1, 2005 a CEN criterion came into effect covering the testing and publication of temperature ratings for sleeping bags. The new criterion differs from the standards that existed formerly.
Sleeping bag labeling 
A European criterion for sleeping bags came into effect on January 1, 2005. This criterion has significant legal connotations for brands, distributors and retailers selling sleeping bags in Europe.
There is a key change to the way sleeping bags are labeled. A European criterion means that all sleeping bags adhering to the criterion will have the temperature ratings set by a standard laboratory test. This means that sleeping bags from different manufacturers will all have comparable temperatures.
There is no legal obligation for brands to conform, as the criterion is optional.
"EN 13537:2002 Requirements for Sleeping Bags" is the official European criterion for the classification of sleeping bags. EN13537 applies to all sleeping bags with the exemption of sleeping bags for military use and sleeping bags for extreme temperatures, i.e., comfort range below -25°C. The criterion was published in 2002 and has now been adopted in most European countries, and also used by numerous outdoor companies outside of Europe.
The criterion is used in the following countries: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, the Netherlands, New Zealand, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland, and United Kingdom.
EN13537 requires a thermal manikin test which produces four temperature results — upper limit, comfort, lower limit and extreme. These temperatures were worked for normal consumers.
The standard measures four temperature ratings:
- 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 purpose of these measurements, a "standard man" is assumed to be 25 years old, with a height of 1.73 m and a weight of 73 kg; a "standard woman" is assumed to be 25 years old, with a height of 1.60 m and a weight of 60 kg.