EN Sleeping Bag Temperature Ratings
EN13537 is the European standard for sleeping bags and requires a thermal manikin test which produces four temperature results — upper limit, comfort, lower limit and extreme. There is no legal obligation to use this standard though most reputable brands do, even non-European ones. There is an exemption for military sleeping bags and sleeping bags for extreme temperatures, ie a comfort range of below -25°C.
Upper Limit: the temperature at which a standard man can sleep without excessive perspiration. It is established with the hood and zips open and with arms outside 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 1.73m (ie 5' 7", not very tall) and a weight of 73kg; a "standard woman" is assumed to be 25 years old, with a height of 1.60m (ie 5' 2.5") and a weight of 60kg.