If you have already shopped for a backpacking sleeping bag, you may be familiar with the temperature ratings of sleeping bags.

However, you may also know that these temperature ratings are often inaccurate.

So you may be wondering how to determine the temperature ratings of a sleeping bag accurately.

While determining the temperature rating of a sleeping bag, there are a certain factors that play a crucial role.

These factors include:

  • Upper Limit
  • Comfort Limit
  • Lower Limit, and
  • Extreme

Well, we will dive into this. But first, let us understand what sleeping bag temperature rating exactly means!

What is Sleeping Bag Temperature Rating?

In simple terms, sleeping bag temperature rating is an indication of how well a bag can perform in providing warmth. This generally gives you the minimum temperature at which the bag is crafted to keep an average person warm in the cold weather.

Sleeping Bag Temperature Rating Determining Factors

Earlier, the temperature of a sleeping bag was determined based on the manufacturer’s best guess. However, when the users tested the bags themselves in various weather conditions, they found the ratings mostly inaccurate.

The reason behind the inaccuracy of a temperature rating is that everyone sleeps at different body temperature. Based on this, there are basically two types of sleepers, hot sleeper and cold sleeper.

Hot Sleepers

You are considered a hot sleeper if you can find a sound sleep without the help of any blankets or comforters. You fall under this category if you have a warm core temperature and your body produces relatively more heat.

Cold Sleepers

If you are more sensitive to cool air, you fall under the category of cold sleepers. The body of a cold sleeper produces little heat resulting in the need for more blankets or comforters. Although you take a nap with every sheet on top of you, you are likely to wake up shivering from cold.

What it Means?: A cold sleeper would want a significantly warmer sleeping bag than someone who is a hot sleeper. Because of this difference in body temperature, the traditional detection of sleeping bag temperature oftens falters.

EN Standard of Sleeping Bag Temperature Rating

Thankfully, there is EN 13537 sleeping bag temperature rating that comes with the following guidelines for the sleeping bags.

Upper Limit: This is a temperature rating at which an adult man would have a comfortable sleep without sweating. It means that if the temperature rises above average, the bag will become too hot.

Comfort Limit: This is a temperature rating at which an adult woman can expect to sleep comfortably in a relaxed position.

Lower Limit: This is a temperature rating at which a standard male can sleep for eight hours in a curled position without any disturbances.

Extreme: This is a temperature rating at which a standard female can remain for six hours without the risk of death from hypothermia. However, there is still a possibility of frostbite. It is also regarded as the emergency-last-resort-temperature.

Testing Factors to Determine Sleeping Bag Temperature Rating

Despite the EN 13537 sleeping bag temperature regulations, the problem remains on measuring how well a sleeping bag can keep you warm on a chilly weather.

There are additional factors that help to determine the temperature rating of your sleeping bag. These factors directly or indirectly affect the sleeping bag temperature rating that is assigned to your bag.

Use of Tent

If you sleep in a tent, it will add about 10-20 degrees of warmth to the rating assigned to your sleeping bag. If you want to camp solo, you will get much heat with a smaller tent rather than a larger one.

Use of Clothing

Undoubtedly, the amount of clothing you wear will also affect how warm you will be. This directly affects the temperature rating of a sleeping bag as you will feel warmer inside the bag with the number of warm clothes you wear. You should take note not to wear cotton clothes if you want to stay comfortable and warm in your sleeping bag.

Use of Sleeping Pad

Another factor that affects the temperature rating of a sleeping bag is the use of a sleeping pad. The value of insulation in your sleeping pad can increase the warmth of your body thus affecting the temperature rating of your sleeping bag. The use of sleeping pads with a higher R-value (higher R-value means higher insulation) helps to keep you more warm and comfortable.

Conclusion

The standard EN regulations have somehow made it convenient to determine sleeping bag temperature rating. However, these standards can be used just as a baseline for comparing the sleeping bags.

As a matter of fact, you should use some of the testing methods to get more insights into the sleeping bag temperature rating. The variables including cold and hot sleeper, use of tent, clothing usage, and type of sleeping pads used somehow affect the temperature rating of a sleeping bag.

It is up to you on how well you can determine the temperature rating of a sleeping bag and how well you can prepare a trip according to it.

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