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Sleeping Bag Temperature Ratings Explained

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 at which 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. The same bag will also have a Comfort limit, in the realm of 32°F, so a woman would be comfortable down to an air temperature of 32ºF. Men and women should always sleep in a layer of long underwear and use a sleeping mat with an R-Value appropriate for expected ground temperatures – without this, the sleeping bag itself is unlikely to keep the sleeper warm enough.

Here’s a basic categorization of appropriate use, based on rated temperatures:
Summer:   >+35ºF / +3°C
3-Season:   +10 to +35ºF / -15° to 0°C
Winter:   <10ºF / -15°C

A huge variety of factors can impact sleeping bag warmth - the above temperatures are merely guidelines, not guarantees. It’s important to think of a sleeping bag as one element in a sleep system which also includes an appropriately insulating sleeping pad and a liner. For instance - if you plan on sleeping in nighttime air temperatures of 27ºF / -3°C, choose a bag with a gender-appropriate rating of 23°F / -5°C nights, plus a sleeping mat with an R-Value of 2.5 to 3, and consider a Reactor thermal liner. If you have any questions about which temperature sleeping bag / R-Value sleeping mat you should select, or how to improve your warmth in a sleep system, reach out to us via our contact page any time.