The EN Rating scale is a scientific test to determine the warmth of a sleeping bag. Unisex sleeping bags list the Lower Limit which is the lowest temperature rating that an average male sleeper would be comfortable in.  Our women’s sleeping bags list the Comfort Limit, which is the lowest temperature rating an average female sleeper should be comfortable. The comfort and lower limit temperature ratings are listed in the features table on the product page. 

For example, a unisex sleeping bag that shows a lower limit of 23ºF means a man should be comfortable down to air temperatures of 23ºF while a woman would be comfortable down to the air temperature of 30ºF, the comfort limit. Men and women should always sleep in a layer of long underwear and use a sleeping mat.

Here’s a basic categorization of appropriate use, based on temperatures:
Summer:   >+35ºF
3-Season:   +10 to +35ºF
Winter:   <10ºF

There’s a huge variety of factors that can impact sleeping bag warmth, so these ratings are not guarantees. We always recommend choosing a bag that is a few degrees colder than you plan on going out in (choosing a 23ºF bag for 27ºF nights). If you have any questions about which temperature you should select, or how to improve your warmth in a sleep system, reach out to us on our contact page any time.