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Sleeping Bag Temperature Ratings Explained

The last thing you want during a night of camping is to wake in your tent shivering cold and grabbing at anything near keep you warm. Not only is this an uncomfortable feeling, but it can also be dangerous. This is precisely why sleeping bag temperature ratings are so important to know.

Knowing these ratings is vital to a good night’s sleep when camping in cold or warm weather. Here you’ll have sleeping bag temperature ratings explained in simple terms to know what you need to shop for.

Camper holding a rolled-up red sleeping bag in a stuff sack.

Sleeping Bag Categories by Temperature

Temperature ratings are most important for choosing how hot or cold you sleep. To be comfortable, you should choose a bag that maintains your warmth at or below the lowest temperature you expect to see on your trip.

First are summer, warm weather conditions, or low elevation bags. These sleeping bags are rated for 32 degrees Fahrenheit and up.

Next is three-season sleeping bags. These bags are rated for areas where temperatures are warm to hot during the day and then drop overnight. The best example of this would be desert locations like the Utah desert.

Finally, you have cold weather or winter, rated for 20 degrees Fahrenheit and lower.

These are just the basic sleeping bag categories, but many for purchase can rate up to negative 20 degrees Fahrenheit for those dealing with icy conditions.

A winter camping tent campsite.

Understanding EN and ISO Temperature Ratings

When looking at sleeping bag ratings, you’ll notice either an EN or ISO rating. EN stands for European Norm, and ISO stands for International Organization for Standardization. Both of these perform the same task, standardizing the method for rating the warmth of sleeping bags.

Before 2017, the market used EN 13537 as the standard testing method. Since then, ISO 23537 has taken its place. This may seem like a lot of abbreviations and random numbers. Still, because of these methods, the testing and safety of these bags are highly regulated—in simple terms, no more freezing cold slumbers or carrying extra unnecessary blankets.

Both methods use a heated mannequin wearing long underwear tops and bottoms along with a hat that is placed on a closed foam sleeping pad. Next, the air is cooled, and the amount of electrical energy needed to maintain the mannequin’s initial temperature is tested.

EN and ISO Rating Levels

So what happens with all the data that starts flowing in? Well, it gets formulated into three different levels. First is the comfort rating, second is the limit rating, and third is the extreme rating.

Comfort Rating

Comfort rating is defined as the air temperature at which an average adult female can comfortably sleep through the night.

Limit Rating

Limit rating is the air temperature at which a standard adult male can sleep for 8 hours without waking.

Extreme Rating

Extreme rating is simply the temperature at which an average adult female can be for 6 hours without risking death from hypothermia.

Temperature Ratings Explained

Another way to think about comfort rating is if you’re a cold sleeper and are always searching for more blankets to cover up with, this is the rating you should pay close attention to. This is the lowest temperature at which your bag will likely provide a good night’s sleep.

On the opposing side, if you’re forever kicking your blankets off and consider yourself a warm sleeper, you’ll want to pay more attention to the limit rating. This is the temperature at which your bag shouldn’t be too hot or cold.

As for the extreme rating, you would never want to solely count on the sleeping bag temperature rating for survival purposes but instead focus on layers, building a fire, or even the structure and integrity of your shelter.

Why Female and Male Limits?

You may wonder, “Why are there differences in male and female limits?” It’s quite simple–biology. During the EN and ISO testings, it was proven that females reported feeling much colder in the same sleeping bag, whereas males felt comfortable.

A woman in a mummy-style sleeping bag covering her lower face.

Determining Temperature Ratings for Children

When looking at children’s sleeping bags, you’ll see various temperature ratings but not EN and ISO ratings. Why? Because children have a completely different physiological and physical makeup than grown adults, and these are what the tests are mirrored after.

Most children’s sleeping bags have a temperature rating of 30 to 40 degrees Fahrenheit which would be good for warmer weather and three-season sleeping. But these are just averages since there is no standardized testing.

A child in a sleeping bag.

Not Absolutes or Perfect Guarantees

As much as these tests are designed to mimic what can happen in nature, they are still only simulations. These tests are done in perfectly controlled environments, so there is room for error when outdoors.

The testing also cannot account for variables like clothing, body types, temperature preferences, weather conditions, sleeping equipment, blankets, pillows, etc.

Everyone has a unique and varying core temperature depending on age, gender, body, and blood flow. This does not discredit sleeping bag temperature ratings, but it doesn’t make them perfect.

Non-EN/ISO Rated Sleeping Bags

After doing all this research, you may find a sleeping bag you like and notice that it doesn’t have these ratings, but why? Not all sleeping bags are required to have EN or ISO temperature ratings, and many do not.

They may mention different temperatures they are good for, but take these with a grain of salt.

Non-rated bags may be questionable, but many manufacturers don’t want unhappy customers, and some of the sleeping bags meet the criteria they say they will. A lot of time, even if they don’t have standardized temperature ratings, they will have a high-quality fill or made of materials that greatly improve the sleeping bag.

Sleeping Bag Designs Effect Temperature Control

Two sleeping quilt-style sleeping bags.

A quick search can prove there are many shapes, styles, and overall designs for a sleeping bag. Some of these designs can affect the temperature inside the bag.

If you’re a comfort seeker, you may be searching for that perfectly roomy bag, but this can lead to air pockets and make you feel more chilled. A mummy-shaped bag has less room to move but will keep you much warmer. It depends strongly on your comfort level and what you’re willing to compromise.

A sleeping quilt is the preferred sleeping method amongst most avid hikers which is more of a blanket style without a hooded top. Although lightweight and easy to carry, these bags cut off at the shoulders, making it easy for all your body heat to escape. Not only is your heat escaping, it also leaves room for cold air to enter.

If you’re brand new to camping or hiking, many experienced campers suggest the mummy style first because of the warmth and comfort it provides. Of course, this is all personal preference and depends on your hiking destinations and camping locations.

How Cold or Warm Do You Personally Run?

Just as the EN and ISO aren’t gospel when deciding on a sleeping bag, a lot is summarized on how warm or cool you personally run.

Gender, age, circulation, and physical fitness levels can affect how your body feels at different temperatures. You may be sitting outside by a campfire with extra layers and a blanket, all while sipping on a hot tea, and the person next to you may only have on a hoodie and jeans. Everyone regulates differently.

Don’t Forgo a Sleeping Pad

A blue sleeping pad or mat.

You may think you have the perfect temperature rated sleeping bag for your new venture, but before you take off in a huff, you should consider looking into sleeping pads.

Not only do sleeping pads boost comfort, but they also help insulate you and keep you off the sometimes below-freezing ground temperatures. Sleeping pads are measured in R-value, ranging between less than 1 and over 8.

A rating of 1 is a summer sleeping pad with very little insulation, and the further up the scale you go, the more insulation, along with higher quality materials. Having the right temperature rated sleeping bag along with the perfect sleeping pad ensures you’re in for one comfortable night’s rest.

Different Ways to Maximize Warmth and Comfort

You can do all the planning, research, and weather tracking you’d like, but mother nature can somehow throw a wrench into all that hard work. There are other ways to keep you feeling warm and comfy even when the weather has different plans.

It’s always a good idea to list cold-weather camping essentials, even if you think it may not be necessary. Ensure you wear the proper baselayers under clothing to enhance your body’s insulating ability, as well as a good winter coat. Down-filled and down alternatives are great when camping in frigid temperatures.

Of course, you can bring more blankets and pillows depending on your camping style (it could be more of a challenge if hiking) to maximize that cozy warmth.

Keeping dry is also essential when camping in cold temperatures. This alone will keep you much warmer, so investing in waterproof gear is incredibly important for these types of treks.

Finally, make sure you have the best winter camping gear. Playing a guessing game with these types of temperatures can be dangerous. This is why just knowing your sleeping bag’s temperature rating is so important.

Frequently Asked Questions

A woman rolling up a green sleeping bag.

Can the age of a sleeping bag affect the temperature rating?

Yes, over the years, your sleeping bag can loose its luster and the amount of down or down replacement it once was filled with. This will indeed change the bag’s temperature rating to a warmer temperature bag than it was once purchased for.

Can you use a 20-degree sleeping bag in the winter months?

There is no one size fits all answer. Sleeping bag temperature ratings are imperfect. It also greatly depends on where you’re camping. Upstate New York winters differ significantly from Florida winter camping.

Why are sleeping bag temperature ratings so important to know?

Knowing how these temperature ratings work is extremely important because the last situation you want is to be cold in the middle of the night because you thought your brand-new sleeping bag was “thick” enough.

These ratings have gone through a vigorous test to ensure that your comfort and safety are at the forefront of your camping adventures.

Is there a “best” temperature rating for a sleeping bag?

There are too many variables to determine a “best” temperature rating. Some are personal preference, body type, camping type, and even location.

Wrapping Up Sleeping Bag Temperature Ratings

A large camping tent with a row of sleeping bags and pillows on the floor.

Knowing the temperature ratings on your sleeping bags is extremely important for comfort level and safety. You could opt for non-rated sleeping bags, but just know that the En and ISO-rated bags have undergone intense testing to be at their stated temperature levels.

Not only are sleeping bag temperature ratings good to know, but also how to keep yourself extra warm and comfortable with other cold weather gear. But to make it even easier, we have broken down how to choose a sleeping bag so you can be on your way to your next adventure.