Best Below-Zero Sleeping Bags

Updated November 2020
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Buying guide for Best below-zero sleeping bags

You might be scaling a rugged mountaintop or enjoying the winter scenery in a National Park, but whatever your reason for camping in freezing temperatures, you need the right gear. Below-zero sleeping bags are suitable for use in temperatures of 0°F and colder, which is well under the freezing point. With the right sleeping bag, there's no environment you can't conquer.

Since you’ll be depending on this sleeping bag to keep you safe in inhospitable conditions, choosing the right one is vital. Arguably the most important factor to consider is the temperature rating, which tells you the lowest temperatures in which the sleeping bag can be used. Other features to think about include the type of insulation, the outer material, and the shape.

Keep reading our full buying guide to learn more about all these features and more. If you're ready to buy now, take a look at our top below-zero sleeping bag recommendations.

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If you're right-handed, it's easier to open a sleeping bag with a left-hand zipper, and those who are left-handed will find it easier to open a right-hand zipper.

Key considerations

Temperature rating

A sleeping bag’s temperature rating is the minimum temperature at which it's suitable for use. Below-zero sleeping bags must have temperature ratings of at least 0°F, but some are rated for use at temperatures as low as -30°F. Of course, most people will never need to use their sleeping bag in temperatures as low as this, but a below-zero sleeping bag will keep you extra toasty when camping in moderately low temperatures of around freezing.

Most below-zero sleeping bags have both a limit rating, which is the minimum temperature for safe use, and a comfort rating, which is the minimum temperature at which you'll feel comfortably warm.

Outer shell

Below-zero sleeping bags need to have an outer shell that is both strong and lightweight, so nylon is by far the most popular choice. Even better than regular nylon is ripstop nylon, which is designed to prevent small tears from getting larger, so if you accidentally snag your bag, the tear should stay under control.

It's nice to have a sleeping bag with a water-resistant outer shell in case excess condensation builds up in your tent and drips on you or you experience levels of rain your tent can't quite deal with. A completely waterproof outer shell isn't a good option, however. It wouldn't be at all breathable, so you'd end up sweating your way through the night.

Insulation

The filling material of a below-zero sleeping bag is hugely important because it's what keeps you warm. Traditionally, real down was the filling of choice for its warmth-to-weight ratio, but newer technology is making synthetic fibers a viable option.

Down is the soft, fine feathers of certain birds, such as geese. Although it's warm and light, it has its issues. First, there are ethical implications surrounding down — vegetarians and vegans will probably want to avoid it for animal rights reasons, and it's less environmentally friendly due to the emissions from factory farming. What's more, down-filled sleeping bags are expensive and can cause allergic reactions or breathing problems in those with asthma or environmental allergies. Down also loses its warming properties when it gets wet, which can be a huge issue.

Synthetic insulation is usually made from polyester or a similar fiber, and many manufacturers have their own patented formulas to make these fibers extra warm and extra light. Below-zero bags with synthetic filling are hypoallergenic, extremely warm and lightweight, and more affordable than real down.

Shape

You'll find two main sleeping bag shapes on offer: rectangular and mummy.

Rectangular sleeping bags give you more room to move around, but they're not as effective at keeping in heat, so you'll only find a few rectangular below-zero sleeping bags out there.

Mummy sleeping bags have a snug fit, gradually tapering from their widest at the shoulders to narrower at the feet. They also usually feature a hood for extra warmth. The vast majority of extreme cold weather sleeping bags are mummy types because of their superior heat retention.

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Did You Know?
Your sleeping bag should come with a compression sack. Stuffing the bag in the sack makes it more compact for carrying and storing.
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Features

Zipper baffle

A zipper baffle is an extra piece of insulated material that lines the back side of the zipper, between the zipper and your body. It's positioned in such a way that it won't interfere with the opening and closing of the zipper. Without a zipper baffle, cold air can easily enter through the small gaps between the teeth, causing a draft and letting out some of your body heat.

Stitching

Sleeping bags tend to have horizontal stitching across them, sometimes in straight lines and sometimes in a curved pattern. This stitching goes through both layers of fabric and the insulation between them. Its purpose is to keep the filling in place; if it shifts around, you could have some areas with a lot of insulation and some areas with none.

Weight

Below-zero sleeping bags can be heavy, with some options weighing well over 12 pounds. Luckily, newer technology means you can also find some exceptionally lightweight options of less than 5 pounds, but the savings in weight can mean sacrificing warmth. Choosing an option in the 6- to 8-pound range may give you a better balance of weight and warmth.
 

Some sleeping bags have built-in pockets for keeping items such as a phone and flashlight close and easy to find.

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Below-zero sleeping bag prices
 

Inexpensive: Below-zero sleeping bags aren't cheap, so even the least expensive cost between $50 and $100. These are usually rated for around 0°F but not much lower.

Mid-range: Spend between $100 and $150 and you can find some fantastic mid-priced options on the market. Some of these are suitable for use in temperatures as low as -30°F.

Expensive: The priciest below-zero sleeping bags cost as much as $150 to $250. These have excellent temperature ratings and are made from the most advanced materials, helping to make them lightweight and comfortable.
 

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Did You Know?
You can find below-zero sleeping bags with hook-and-loop tabs that let you remove your arms without unzipping the bag. 
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Tips
 

  • Know what the ratings mean. There’s a difference between the comfort rating and the limit rating. The comfort temperature rating is the lowest temperature at which you'll feel comfortable in your sleeping bag, while the limit rating is the lowest temperature at which the sleeping bag will keep you safe from the elements even if you feel quite cold.
  • Check the size. Some sleeping bags are available in several lengths to suit people of different sizes. Also, check the width to make sure you'll fit inside comfortably.
  • Add a layer of insulation between you and the ground. This makes more of a difference in how cold or warm you feel than you might realize. The insulation can be anything from a basic camping sleeping pad to a luxury camping mattress.
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It's better to have a below-zero sleeping bag that's slightly warmer than you need than not warm enough. If you get too hot, you can always remove a layer or two of clothing.

FAQ

Q. Is it really safe to camp in below-zero temperatures?

A. It certainly isn't that comfortable to sleep in temperatures of 0°F and below, but it's safe if you have the right gear. Of course, you need your sleeping bag, but you also need an appropriate four-season tent and the correct clothes to stand up to such low temperatures. Sleeping outdoors in these temperatures isn't for the casual camper but rather for mountain climbers and other adventurous folks. That said, some people sleep outdoors in cold weather out of necessity. For homeless people in cold climates, a below-zero sleeping bag can mean the difference between life and death. You might want to donate a below-zero sleeping bag to a charity or organization that helps homeless individuals in your local area.

Q. How will I know which temperature rating is right for me?

A. Temperatures fluctuate even when you compare the temperature on the same day from one year to the next, so it's impossible to know exactly how cold it will be where you're camping. Therefore, you should choose a sleeping bag with a temperature rating that's suitable for the lowest possible temperature at the time you'll be camping, even if it doesn't usually get quite that cold. That way, you won't get caught out if it's colder than average.

Q. What is a footbox on a sleeping bag?

A. With a mummy sleeping bag, you want a snug fit over the legs, but, when lying down, your feet stick up vertically. A footbox is sewn in such a way to accommodate your feet without losing the snug fit around the legs. If you have larger-than-average feet, it's important to check the size of the footbox to ensure a comfortable fit. 
 

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