An EN rating (European Norm 13537) is a testing and rating system that standardizes sleeping bag temperature ratings across manufacturers into a relatively easy to understand and comparable scale. Achieved by measuring thermal efficiency utilizing a sensor-equipped mannequin in a specialized environment, the results of an EN Rating are comprised of 4 parts, and generally you’ll just focus on the comfort rating (women), and the lower limit (men).

Backpacking sleeping bags that have an EN Rating allow you to compare different bags all on the same scale.

EN Rating Terminology

Upper Limit

The highest temperature that the average adult man can sleep in comfort.

Comfort Limit

The lowest temperature at which the average adult woman can sleep comfortably.

Lower Limit

The lowest temperature at which the average adult man can sleep comfortably.

Extreme Limit

The lowest survivable temperature for the average adult woman.

Do All Manufacturers EN Test?

Many mainstream manufacturers are now having their bags EN tested to remove the variability that may come with a manufacturer-determined rating. However, many manufacturers of excellent bags choose to skip the process of an EN test and stick with more traditional means when it comes to providing a temperature rating for their sleeping bags.

For plenty of EN Rated sleeping bags, see this page at REI Co-op, and for more on backpacking sleeping bags, see our guide on How to Choose the Best Backpacking Sleeping Bag.

Editor’s Note: This article originally appeared in Issue 25 of TrailGroove Magazine. You can read the original article here.