What Is a Compression Sack? (Sleeping Bags)

What exactly is a compression sack? It sounds kind of awkward if you ask me. Let’s not mince words.

A compression sack is a bag that is intended to compress the contents so it will fit in a smaller space. Compression sacks often have straps that go along the sides and ends that can be tightened to compress even more. Compression sacks are often used for otherwise bulky sleeping bags.

Since modern sleeping bags have something called “loft”, which effectively measures how much air the insulation can trap, a great way to reduce their size for transport is to push out all of the air in the sleeping bag. Compression sacks do exactly that, which means they’re great for packing a warm, puffy sleeping bag into a relatively small backpack.

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Now that you understand the fundamentals of what a sleeping bag compression sack actually is, we can start to dive into the nitty-gritty details of the world of compression sacks. Coming up, we’ll discuss whether or not you actually need a compression sack, how they’re different from other types of stuff sacks, and how compression sacks affect your sleeping bag. We’ll also give you some tips for determining the correct size compression sack for your sleeping bag and we’ll talk about the value of a waterproof compression sack. Let’s get to it!

compression sack for sleeping bag
You’ve just bought that brand new sleeping bag for your next camping trip but the salesperson at your local gear store mentioned that you’ll need a compression sack for backpacking. But what is a compression sack for a sleeping bag and how do you use it?

Do I Really Need a Compression Sack for My Sleeping Bag

Like all good questions, the answer to this one is, well, it depends. There are some people who swear by compression sacks and others who refuse to use them. Although there’s no single correct answer here, we can offer you some advice as to when a compression sack might be useful.

If you have a sleeping bag with a lot of loft, such as an 800+ fill down bag, a compression sack can help you squeeze the bag down into its smallest possible size by pushing out all of the air. This can be useful for people on long backpacking trips (7+ days) who need to maximize every square inch of space in their pack for all of their food and fuel. People with particularly large and bulk synthetic sleeping bags also often enjoy using compression sacks because they can make the sleeping bag a bit easier to pack.

It is important to note, however, that putting a sleeping bag into a compression sack does turn it into a rather oddly shaped hard-sided object. Depending on your backpack shape and size (e.g. long and narrow), it can actually be more difficult to pack a filled compression sack than it would be to just stuff the sleeping bag into the bottom of your pack.

That being said, compression sacks offer more benefits than just reducing the size of your sleeping bag. They can help protect your expensive sleeping bag from dust, dirt, and debris. Plus, using compression sacks and stuff sacks can make it easier to keep your gear organized while you’re in the backcountry.

How To Pick The Right Size Of Compression Sack

Determining the right size compression sack for your sleeping bag can actually be quite tricky. Luckily, the vast majority of modern backpacking sleeping bags actually come with their own specially-designed compression sack, so you might not need to worry about this. But, if you buy your sleeping bag second hand or you’ve lost the compression sack, you’ll need to determine what size you actually need.

The absolute easiest way to figure out what size compression sack you need is to contact the manufacturer of your sleeping bag. Chances are good that they can either give you a new compression sack for free or sell you one at a reasonable price. If not, or if you’re looking to buy a waterproof compression sack from a different company, the sleeping bag manufacturer can probably tell you what size you’ll need.

If you can’t remember the make and model of your sleeping bag, then you’ll have to do some sleuthing to figure out what size compression sack you need. Generally speaking, the warmer the sleeping bag (e.g. the lower the temperature rating), the larger the compression sack. Moreover, synthetic sleeping bags usually need a larger compression sack than their down-filled cousins.

To estimate the size compression sack you’ll need, you can do the following:

  1. Find a cardboard box that is slightly larger than your sleeping bag
  2. Measure the cardboard box’s length and width
  3. Stuff your sleeping bag into the cardboard box and press down on it firmly until the upper surface of the sleeping bag is approximately level
  4. Measure the depth of the box that the bag occupies
  5. Multiply length x width x depth to get the volume of the stuffed bag in cubic inches
  6. Divide this volume by 61 to get the volume in liters. Voila!

The Difference Between Storage Sacks, Compression Sack, and Stuff Sack

If you do enough research on sleeping bag storage and packing, you’ll hear a lot about storage sacks, compression sacks, and stuff sacks. Unfortunately, many people confuse these term and treat them as if they were the same thing when really they’re completely separate entities.

Storage sacks are specifically designed to protect a sleeping bag when it is in storage. These sacks are usually about the size of a large pillowcase and are meant to make it easy to store a sleeping bag without compressing it too much. Some storage sacks are mesh, while others are made of cloth, but usually, sleeping bag manufacturers provide these when you buy a new bag.

Stuff sacks, on the other hand, are small nylon bags used to store anything from spare clothes to toiletries. They come in a variety of sizes, from 2L, all the way up to 30+L, so they’re not necessarily sleeping bag-specific pieces of gear. Sleeping bag manufacturers usually include these when you buy a new bag and they’re helpful for packing or transporting sleeping bags. Stuff sacks do compress a sleeping bag, but not as much as a compression sack.

Compression Sacks, on the other hand, are effectively stuff sacks with an additional set of straps that help you push the air out of a sleeping bag. Depending on the sleeping bag you own, a quality compression sack can reduce the stuffed size of your bag by almost 60-75%.

Do I Need A Compression Sack For My Sleeping Bag?

The truth is, you don’t need a compression sack at all for your sleeping bag. In my opinion, they are very nice to have while you’re backpacking because they protect your sleeping bag from dirt and you can get them much more compact that way, but you can get away without one. In fact, you don’t need any kind of bag at all to pack a sleeping bag!

You can always simply roll up your sleeping bag and use bungees or ropes around the sleeping bag and attach it to the back of your backpack. I recommend putting some sort of covering for your sleeping bag (can be a trash bag) just to keep it protected from dirt (not to mention water).

Can a Compression Sack Ruin a Sleeping Bag?

There are plenty of rumors floating around on outdoor forums on the internet that compression sacks can ruin a sleeping bag. This is a fair enough concern, of course, since the last thing you’d want to do to your expensive sleeping bag is destroy it forever. Luckily, we’re here to tell you that, while yes, improper use of a compression sack could decrease your sleeping bag’s insulative properties, this isn’t really the whole truth.

In reality, the only true way to “ruin” a sleeping bag with a compression sack is to stuff your sleeping bag into one and leave it there for about a year. Doing so won’t render your sleeping bag useless, but it will likely compress the down or synthetic fill and reduce the overall loft of the bag, making it slightly less insulating than before.

Thankfully, there’s an easy way to avoid “ruining” your sleeping bag: only use a compression sack when you’re packing your sleeping bag into your pack for transporting it to the next camp. Never store your sleeping bag in a compression sack for more than a couple of days, maximum, and it’ll be just fine.

Are Compression Sacks Waterproof?

The short answer is no, compression sacks aren’t always waterproof. The good news, however, is that you can buy compression sacks that are waterproof!

For the most part, the compression sacks you’ll get when you buy a sleeping bag won’t be waterproof but you can buy special waterproof compression sacks from a variety of manufacturers, like Sea to Summit. These waterproof compression sacks combine the benefits of a dry sack with those of a compression sack for the ultimate protection for your sleeping bag.

Waterproof compression sacks are great if you live or travel in particularly wet locales as they can add an extra layer of protection between your new down sleeping bag and the rain. The main downsides of waterproof compression sack are that they tend to cost a bit more and weigh slightly more than non-waterproof varieties.

Do Backpackers Need a Compression Sack?

Backpackers are perhaps the main group of people who benefit from using a compression sack. Since they have limited space for storing and transporting gear, anything that can be done to reduce the bulk of an object is often much appreciated by a backpacker. Ultralight backpackers, however, often don’t like to use compression sacks as they do add a small amount of weight to one’s pack.


Ultimately, sleeping bag compression sacks can be incredibly useful pieces of gear when used correctly. They can help reduce the bulk of a high-loft sleeping bag while protecting your bag from the elements. Waterproof compression sacks are also great for backpackers and outdoor enthusiasts who like to adventure in wet environments but don’t want to curl up into a soggy sleeping bag at the end of the day. Whether you choose to use a compression sack or not, you can now go forth into the world with a bit more knowledge about them than before.


Peter is a software developer who loves to take every opportunity to go outside that he can get. Peter grew up going on long backpacking excursions with his family every Summer and now enjoys staying at the beautiful Texas State Parks and swimming in the amazing Texas Rivers.

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