selkbag camping sleeping bag

Understanding Temperature Ratings

April 27, 2020


Sleeping bag temperature ratings are a somewhat complicated subject - we feel you - Comfort? Extreme? Limit?...... what the hell?

To understand them better, it helps to understand how the bags are tested for warmth in the lab (including some of the limitations in the process), and the meaning of some not-so-intuitive terms you’ll see in Selk'bags temperature ratings.

Here are important things to understand when using temperature ratings to shop for a sleeping bag:

  • Lab-tested temperature ratings (as indicated by “EN” or “ISO” ratings) are useful for making an apples-to-apples comparison between sleeping bags from different brands.
  • Real-world comfort probably won’t match lab-tested temperature ratings because of all the variables that a lab can’t simulate.


In the old days, brands tested sleeping bags in their own labs using a variety of methods, so there was no way to know if one company’s 30-degree bag was truly just as warm as another’s 30-degree bag.

The bag industry solved this problem by agreeing to test bags the same way for all brands. Today most brands send their sleeping bags to an independent test lab that assigns bag temperature ratings.

EN (European Norm), was the original standard adopted by the sleeping bag industry. Today, a new entity, the ISO (International Standards Organization), oversees bag testing, but the method is almost identical to the EN bag test. 

Standardized laboratory tests produce a rating range for each sleeping bag, with two temperature ratings within that range specifically called out:

      • Comfort rating indicates the temperature at which a standard woman wearing nothing but the Selk'bag can expect to sleep comfortably in a relaxed position.
      • Lower rating (which is always lower than the comfort rating) indicates the temperature at which a standard man wearing nothing but the Selk'bag can expect to sleep comfortably in a relaxed position. 


Temperature ratings are estimates, not gospel: Lab testing simulates how a sleeping bag should be used: A sleeping pad is placed under the bag, and a test dummy inside the bag is dressed in base layers. While this protocol ensures that all bag tests are done the same way, it can’t account for variations like differences in people’s clothing and gear (i.e. sleeping pads), differences in body types (warm and cold sleepers), changing weather conditions, differences in food people eat and more. So, when you use your sleeping bag in the outdoors, its comfort level will probably differ from its tested temperature rating.

Why women’s sleeping bags use the comfort rating: Data on physiological differences between traditional genders has always shown that the “average woman” will feel colder in the same bag than the “average man” will feel. So, the comfort rating, which is the temperature for colder sleepers, was the logical spec target for women’s.

Not every sleeping bag has an ISO (or EN) rating: The test standard isn’t valid for bags designed for extreme cold, nor does it apply to kids’ bags. And brands might not choose to get ISO testing on bags intended for mild conditions or casual use. Whenever you see a “temperature rating” spec that’s not stated as either “comfort” or “lower limit,” that bag spec probably reflects the brand’s estimate, not an ISO or EN test. Use that spec as a rough guideline, not a rating you can absolutely compare to similar bags from other brands. On Selk'bag case, you will always see our rating temperatures on the hangtag and on our website so you can check that information at the moment of buying. 


2 Responses

Jeri Erickson
Jeri Erickson

February 15, 2022

I’m so impressed by the outstanding ⭐️⭐️⭐️⭐️⭐️ customer service. Cheryl , thank you . You have been a pleasure to work with . This company is going to do everything by hey can to make sure you love your SELK bag. Do not hesitate to order. You will get exactly what you want. And I needed to go up a size and I had no issues . I felt so comfortable dealing with them . It felt like was ordering from my friends company .

Matthew Hampton
Matthew Hampton

February 15, 2022

Selk’bags are the future and the future is now. I have been following sleeping bag and comfort technology for decades and am happy to say that this is the most meaningful breakthrough in outdoor comfort living I have seen. The selk’bag is the culmination of tens of thousands of years of human innovation!

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Size Chart

A proper fit is essential to fully enjoying all the Selk'bag has to offer. All Selk'bag models are unisex, meaning that is suitable for men and women.

The size you need will depend on the activity you'll use it for the most : to sleep, be active, both, or any other thing you may think of. To help you choose we’ve put together a Fitting Guide with comprehensive information.

In case you still unsure which size to choose, please contact us anytime and we'll be glad to help!


Size Medium
Minimum Height: 4'0" / 122 cm
Maximum Height: 4'6" / 137 cm
Size Large*
Minimum Height: 4'6" / 137 cm
Maximum Height: 4'11" / 150 cm
 * Please note, Kids size Large is significantly less wide than the Adult size Small.  An adult that measures between 4'6" / 137 cm and 4'11" / 150 cm should use the Adult Small over Kids Large.


Size Small
Fits up to 4’11’’ / 150 cm Tall
if you are between 4’5” and 4’9” this is your size.
It can fit up to 4'11'' if you intend to use it while active, without booties.


Size Medium
Fits up to 5’5’’ / 165 cm Tall
If you are between 4'9'' and 5'3'' this is your size. It can fit up to 5'5'' if you intend to use it while active, without booties.


Size Large
Fits up to 5’11’’ / 180 cm Tall

If you are between 5'3'' and 5'9'' this is your size. It can fit up to 5'11'' if you intend to use it while active, without booties.


Size X-Large
Fits up to 6’4’’ / 193 cm Tall
If you are between 5'9'' and 6'2'' this is your size. It can fit up to 6'4'' if you intend to use it while active, without booties.


Size X-Large Wide
Same as X-Large, but for heavier body types (approx. +2'' in girth throughout the torso vs X-Large)

Realtree models only


* Please keep in mind that our Original model, due to a higher insulation loft (contains more padding insulation than the Lite) makes it more snug, so we recommend to size up if you are 1'' to 3'' below the in between size range (i.e if you are getting the Original 6G and you are 5'9'' we recommend getting an XL)


In-between sizes? 
A looser fit is better for more comfortable sleeping, while a tighter fit is better for mobility - but may restrict sleeping comfort if booties are left on.

We always recommend to size up if you are in between sizes or not completely sure. It's better to have a little bit more room while using your Selk'bag!