Your sleeping bag is one of your most important pieces of gear when it comes to the backcountry. So it’s important for you to choose the right sleeping bag for your needs.

With that being said, sleeping bag temperature ratings can be very complex, so it can be difficult to know what will be necessary for your adventures.

That is why I’m here today.

This article will help give you a total breakdown of sleeping bag temperature ratings and what they actually mean.

 

Without further ado, let’s jump into the article!

 

 

For more information on sleeping bags, I love what Sea to Summit has to offer. Here is a link to their website. https://seatosummit.com

 

 

What are Sleeping Bag Temperature Ratings?

 

 

A sleeping bag temperature rating is a number that a manufacturer put on their sleeping bags. The whole purpose of this, is to help you have a better idea of the best conditions for using a specific bag.

To give you a better idea, a 40°F (4°C) sleeping bag is mostly considered a “summer sleeping bag” in moderate climates. On the other hand, a 20°F (-29°C) sleeping bag would be more of a “winter sleeping bag.” This type of temperature rating will be suited for the colder months of the year.

With so much technology and science being tested on an annual basis, understanding how these rating systems work together is important if you want the correct gear for camping.

 

 

Understanding the EN/ISO Rating Standards.

A long time ago, there was no universal standard when it came to temperature ratings in a sleeping bag.

This meant that manufacturers could, more or less, label their gear with any rating that they saw fit.

You can only imagine the confusion this would cause.

Not to mention, the number of people who were irate and frustrated that their sleeping bag didn’t keep them warm enough even in the summer months.

In 2005, The international Organization for Standardization (ISO), introduced a standard knowns as the EN-ISO 13537.

This standard was more of a systematic rating system among all of the world’s leading sleeping bag manufacturers. With that being said, this created an independent testing system that takes the responsibility of testing away from the manufacturers to ensure that everyone around the globe can get the gear they need.

But like anything else, this rating system has evolved over the years and it is now known as ISO 23537. Nothing has really changed, though they’ve become more rigorous and refined over time.

 

The Sleeping Bag Rating Test and What it Actually Means

 

 

To give us a better idea on how to use the rating system to purchase the right sleeping bag, it’s important to have good background knowledge of the tests used to rate these sleeping bags in the first place.

The test itself is quite complex and specific.

Basically, testing companies will use a heated manikin that’s covered in sophisticated sensors instead of a human being. They place this manikin inside a sleeping bag and on a foam sleeping pad inside a cold chamber.

During the testing process, they will evaluate the data they get from said sensors. They are looking for the following benchmarks, Let’s take a look at what they are….

• How long does it take for the manikin’s heat to build up in the sleeping bag?
• What temperature does heat escape the bag?
• Does the sleeping bag maintain a steady temperature?
• At what temperature does the sleeping bag become ineffective?

 

So, all of this data is loaded into computer models, which then spew out a series of numbers. These numbers are then being evaluated by professionals and they’re used to also determine the various sleeping bag rating limits that you see when you purchase your sleeping bag.

 

 

Temperature ratings are just estimates, not the gospel.

Lab testing simulates lots of things, but not everything.

While this protocol ensures that all bag tests are done the same way, it can’t truly predict and account for all of the variations like differences in people’s clothing and specific gear, changing weather conditions, differences in food people eat and more.

So, when you use your sleeping bag outdoors, its comfort level will probably be different than 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 than the average man.

So, the comfort rating, which is the temperature for “colder sleepers”, was the logical spec target for women’s bags, and brands continue to use the comfort rating on women’s bags you see today.

More comfort also means more weight.

This is the result of using the comfort rating test result for women’s bags. It takes more insulation to ensure one bag’s comfort rating matches another bag’s lower limit rating. If you tend to be a warmer sleeper, than you can shed off a few ounces of weight by choosing a lower rating.

 

What you Wear while Sleeping is Important

Like I said before, no sleeping bag rating can take into account every possible situation, so they don’t factor in what you’re actually wearing when you go to sleep. As you can imagine, someone wearing several layers while sleeping is going to be much warmer than someone wearing a pair of shorts.

This means that you actually have a little bit of control over how warm you are at night, even if you only have one sleeping bag at your disposal. If you feel like you need added warmth, you can always use a sleeping bag liner to increase the overall warmth of your sleeping bag.

 

Sleeping Pads Make a Difference

 

Another important piece of gear to invest in is a good quality sleeping pad.

Sleeping pads are designed to give you added comfort and insulation from the cold ground. Since sleeping bag temperature ratings are tested while using a sleeping pad, it’s imperative that you use a quality model with an appropriate R-Value to get the same results.

In reality, it doesn’t matter how warm your bag is if you don’t have a quality pad to go with it. Klymit and Nemo have excellent options for sleeping pads. I am a fan of both companies because of the way they test their pads in the backcountry.

 

What is R-Value Anyways?

A sleeping pad’s R-value measures its capacity to resist heat flow through it.

The higher a pad’s R-value, the better it will help insulate you from cold surfaces. This ranges from less than 2 (minimally insulated) to a 5.5 or higher (very well insulated). Up until 2020, there was no standardization for how companies measured R-value.

Therm-a-rest and Sea to Summit, for example, had their own testing facilities, while brands like Exped used third-party researchers to do the testing for them. As a result, one brand’s 3.2 might be another brand’s 4.5- meaning there was no way to really compare. The good news is this all changed in 2020. Thanks to these companies such as Therm-a-rest and REI, there is now a standard for R-values. Similar to the ISO/EN rating for sleeping bags, the objective is to allow consumers to compare a variety of pads like for like.

 

When and Where Do You Use a Sleeping Bag Most?

To help the selection process easier, first you should decide when you will be using your sleeping bag. If most of your camping is in the desert during the summer, you don’t need a 0°F bag. On the flip side, if you spend a lot of time doing backcountry ski trips in the winter, you don’t need a 30°F bag.

It’s also important to consider the terrain you’ll be sleeping in. Temperatures in the mountains can change dramatically as storms quickly roll in. Desert temperatures can drop a lot at night, but the weather patterns are generally more stable and predictable.

Once you’ve decided where you’re spending the most time camping and knowing what the weather is like in those locations, makes picking a temperature rating a lot easier.

 

 

Thoughts & Takeaways

And that wraps things up for today. Choosing the proper temperature rating for your sleeping bag will help you be safe and comfortable. I hope this article made sense and brings clarity when it comes to understanding sleeping bag temperature ratings. Unfortunately, like many categories of outdoor gear, there is no “one bag fits all” temperature rating. If you plan on doing mid-summer camping at lower elevations or heading to the desert, a true summer bag with a 30-50 degree temperature rating will be enough to suffice. But if you’re planning on heading out in the winter at higher elevations, there’s no way getting around getting a true winter sleeping bag combined with a high R-value rated sleeping pad to go along with it. If you have any questions regarding sleeping bag temperature ratings, please ask me in the comment section below.

 

 

 

-CT