What Is The Worlds Warmest Sleeping Bag? We Found And Tested It.

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One of the most common questions I hear from readers is about cold weather sleeping bags, especially, What Is The Warmest Sleeping Bag. You may have heard the saying, ‘it’s better to be too warm than too cold, and that saying holds true, especially where you may find yourself winter camping in backcountry.

This article will look at what makes a warm super warm sleeping bag, give our recommendation and go through some essential sleeping bag features to help you make the right decision.

Our recommendation

After receiving many readers suggested products, performance testing and ordering some of the highest temperature rated sleeping bags from Amazon and REI, our recommendation for The Warmest Sleeping Bag is the Pajak Sport Radical 16H (-73°C / -99.4°F). The second sleeping bag is the Hispar 1200 Down Wet Sleeping Bag: K Series (-58°C / -72.4°F).

Named their ‘warmest and best sleeping bag ever’, this record-breaking bag is rated for temperatures of -73° Celsius or -99.4° Fahrenheit.

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In comparison, some of the closest cold rated sleeping bags we researched came in at 10-20° Fahrenheit higher, including:

The Pajak Sport Radical 16H is only available online through their official website, but just a word of caution. The price tag on the Pajak Sport Radical 16H is $1,600 USD, making it the second most most versatile sleeping bags we reviewed. 

So if you’re planning on a trip to Antarctica and price is not a concern, then there is no comparison to this lightweight extreme, temperature sleeping mummy bag.

Pajak Sport Radical 16H

ISO 23537 makes it The World’s warmest Winter bag.


900 FP Polish White Goose Down Fill, -73 [C], Fill weight 1050 [G], Weight 1500 [G], Temperature Rating -73 Degrees, Comes With Stash Pocket / Storage Sack

Product Summary

One of the lightest bags that can withstand minus -73 [C] temperature ratings at just over three pounds. The Pajak Sport Radical 16H features a 900 down fill and a gossamer-like nylon outer shell that completes it’s puffy look.

The Pajak Sport Radical was really made with Antarctica in mind or for high altitude summit pushes. The three-time Polish ski mountaineering champion Andrzej Bargiel trusts the Pajak Sport Radical 16H on his widely covered K2 attempts.


  • Will retain 50% of your body heat for a warm night’s sleep
  • Constructed like a Russian Doll excellent warmth to weight ratio
  • The lightest bag has equal distance between the outer shell and lining
  • H constructed chambers are filled with a down accuracy of 0.02g

Affordable sub-zero sleeping bags

If you are like me and rarely camp in sub-zero conditions or have the budget for a sub 60 sleeping bag, here are a few high performing cold weather sleeping bags that are a fraction of the cost.

Coleman Brazos Cold Weather Bag 20°F

A quality performer at an affordable price


100% Hollow Polyester Fill, 20[F], Polyester Outer, Weight not specified, Temperature Rating 20 Degrees, Comes With Stash Pocket / Storage Sack

Product Summary

You’ll stay warm and cozy on cold winter nights under the stars with the Coleman Cold Weather 20º F Brazos into your stuff sack for campouts during colder months. Its durability means that it lasts for seasons after seasons.

The bag is also equipped with an innovative ventilation system, which allows air to flow from the top to foot box of the bag without compromising its warmth. The result is a comfortable night of sleep even at sub-freezing temperatures.


  • Roll Control, locking mechanism to reduce movement while packing
  • ZipPlow, intuitive zip design to reduce snags
  • Quick Cord, a snappy design to help you pack the bag faster
  • Comfort Cuff, layers the zip to minimise body contact
  • Thermolock, zipper heat retention system

Bessport Sleeping Bag Winter 18°F

cotton flannel lined layer for a relaxed feel


350GSM spray-boned cotton filling, 18[F], Polyester Outer, Weight 4.7lbs, Temperature Rating -23 Degrees, Comes With Stash Pocket / Storage Sack

Product Summary

The Bessport is an Amazon Choice product with over 800 positive reviews. It features high-loft inner made of polyester lined with flannel for that natural home feel. It’s perfect for cold temperatures and rated for temperatures 23-23°F/-15°C.

The outer polyester fabric is water repellent which may seem standard but not all versatile sleeping bags we have convered have a water proof outer. The zip is tempered and double sided with an anti snag detail which will provide years of durability and protection from lining tears.


  • Roomy, can suit a person of 6’6 in stature
  • Water repellent and machine washable without distorting the fill
  • Constructed pockets for your smartphone

Coleman Silverton mummy sleeping bag

An upgrade of the Coleman 0°F Mummy


Colethem Hollow Polyester Fill, 0[F], Polyester Outer, Weight not specified, Temperature Rating 0 Degrees, Comes With Stash Pocket / Storage Sack

Product Summary

Featuring Coletherm, Colemans patented polyester insulation technology, the Silverton is one of Colemans lowest rated cold weather sleeping bags.

Rated for 0 degrees fahrenheit the Coletherm inner and Thermolock draft work well together to surround the entire body with retained heat and reduce cold spots.


  • Coletherm, polyester cycle technology which distributes heat evenly even in wet weather
  • Thermolock, reduces heat loss from the zipper
  • ZipPlow, inuitively pushes material away from the zip to reduce snags

How does a sleeping bag keep you warm?

It is said that the best sleeping bag is not the one with the most padding. Instead, it’s the one that fits you best that will make you sleep comfortably. Essentially, a extreme temperatures bag is a large encasing garment that wraps around you to keep you warm.

It keeps you warm by providing a snug/sure environment that traps and keep body warmth inside its enclosed environment while allowing for enough airflow to allow the user to get a good night’s sleep.

What are sleeping bags made from?

Sleeping bags often vary in weight, comfort level and materials. Sleeping bags are commonly made up of either synthetic fibre or down. They may also be insulated with a layer of foam or fill material like nylon, polyester or down fill.

One common thing with sleeping bags is their construction. Most on the market feature a layer of synthetic waterproof fabric and insulation between the fabric and your body, commonly fleece or down feathers, felt or wool.

Synthetic versus down sleeping bag material

There are two top contenders for the warmest and most durable bag materials: synthetic or down-padded. Synthetic bags are lighter and warmer than down-filled bags but rarely offer as much fill power warmth or comfort.

Down-filled rectangular sleeping bags can be warmer than synthetic bags and have a natural feel similar to cotton. However, there are a few downsides to down fills; down will be heavier and bulkier than a synthetic filling, thus taking up more valuable backpack space. 

Down fill can also take a lot longer to dry out should you accidentally get your sleeping bag wet.

When should you use a sub-zero sleeping bag?

If you live somewhere where there is no snowfall for months on end (like Australia), then you might not need a zero/sub-zero degree sleeping bag. But if you live somewhere where it snows throughout the year, then a zero degree sleeping bag would be beneficial because this type of sleeping bag is meant for the freezing or very extreme environment.

Additionally, you may want to add a sleeping pad or sleeping bag liner to a sub zero to these warm bags to reduce cold air between the ground and your body.

Things to consider when buying the right sleeping bag


These bags are bulky compared to three or four-season sleeping bags. Many have specialised materials for retaining heat, and should the weather end up warmer than expected; then you may have an unused extreme cold weather sleeping bag taking up a lot of backpack space.


The durability of zeros differs from model to model. Some models may last up to five years, while others may only last a year or two. But because they are specifically made for the most extreme conditions, they will come at a significantly higher premium than seasonal mummy bags.


This includes such things as waterproofing, warmth rating (how easy it is to stay warm), venting system and even quality of the stitching – It should be strong enough so that it will last through many times.