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Sleeping Bag Liners: What Are They, How to Use & Warmth

Read Time: Approximately 9 minutes

A sleeping bag or backpacking quilt is used to keep you warm when out on the trail and this can have two impacts on a long-distance thru-hike. The gear will get dirtier and dirtier over the days of grime along with starting to perform worse than rated for heat due to this build-up, so what does a sleeping bag liner do?

A sleeping bag liner provides you a layer between you and the bag or quilt that can help keep the temperature more favorable as well as it is much simpler to wash a liner than to wash a bag or quilt. Liners come in different materials to help keep temps up and down depending on your needs.

While reading I found that these are also known as a sleeping bag sleeve, though I haven’t heard that myself before. So now that you understand the first huge benefit for a thru-hike in being simple to clean we can dig in deeper as to what they are and why they are a simple way to improve your gear for a low cost.

Woman in a red sleeping bag using a sleeping bag liner inside to keep her warmer and clean.

What Is a Sleeping Bag Liner?

So for those who haven’t seen these before and aren’t familiar with them a sleeping bag liner is a thin layer of fabric that is basically shaped like a cocoon, it surrounds you and keeps you from coming into contact with your sleeping bag or quilt.

A liner is able to become that vital layer between you and your body oils, dirt, and grime which is incredibly easier to clean and maintain on the trail without the issues of washing down, which is a difficult thing to accomplish on the trail even on a zero.

Is a sleeping bag liner necessary?

The next question would be based around having another piece of gear that provides only one purpose in general to a set of backpack gear. While I can say it isn’t required and many may not have tremendous issues with quilts getting so dirty the performance is impacted, but each person is unique so you should think about it.

If you are someone prone to getting dirtier on the trail or are using very gentle gear, like that 950-1000FP down top quilts, then sometimes this layer can help you have a high-quality performance from this gear for the entire trail for little weight and space.

Is sleeping bag liner important?

Overall I would rate it is not “important” for the trail, you can definitely hike without one but you will end up spending much more time once at home or in town if you find you need to wash gear as you need lots of specific soaps for a sleeping bag or quilt.

How much warmth does a sleeping bag liner add?

The extra warmth that a liner can provide can be huge in cold weather, like this one which is a mummy liner that provides up to 25 degrees warmer performance via normal or synthetic materials, though it was designed to help aid warmth beyond most other options.

A bag liner adds anywhere from 5° to 15°F of warmth to your sleeping bag or hiking quilt, depending on the materials used to make the liner. In hot places, a bag liner could be used like a travel sheet where you could bypass using your sleeping bag or quilt during warmer summer months.

The other side of liners is that there are some, like a silk liner, that can help you stay cooler in warm climates that can help you get better rest than you may otherwise get.

What Does a Sleeping Bag Liner Do For You?

For a hiker who will spend 5-7 days out and away from civilization, you wouldn’t probably be surprised at how dirty and gross you can get in short order, this is why I choose to carry a liner with me on many hikes.

Sleeping bag liners are placed inside your sleeping bag to retain it clean and add extra warmth. Dirt and grime from the exterior, however, might get in and damage your gear which can be costly to clean or replace if enough damage is dealt with.

There are some very valuable benefits to a liner that should be discussed so that if you are for it or against it you can make an informed decision as to whether you should carry one.

Providing Additional Warmth

In general, sleeping bag liners add an average of 10 degrees Fahrenheit of warmth to a sleeping system. This is due to the layer of insulation that they provide, trapping heat close to your body and preventing it from escaping.

If you are someone who consistently battles the cold, then having a sleeping bag liner can be incredibly beneficial in ensuring that you stay comfortable and warm throughout the night.

Helps Keep Your Bag Clean

One of the biggest benefits of using a sleeping bag liner is that it helps to protect your sleeping gear overall from dirt, grime, and body oils. This can be incredibly beneficial, as it can help to keep your sleeping bag, quilt, and sleeping pad in good condition for longer, and prevent them from becoming damaged or stained.

Can Be Used in Hotels/Hostels

I hate to say it but bed bugs and gross crap exist and are often in hostels or other places where you are sleeping on a mattress, etc. Sleeping bag liners can be used to help protect you from anything the site may have from previous hikers.

Ability to Use on its Own

When it gets warmer outside, you can use a sleeping bag liner as a standalone sheet. This is perfect for those who are traveling in hot climates, as it will help to keep you cool and comfortable during the night.

What Are Sleeping Bag Liners Made Of?

There are multiple types of fabrics that can be used to make the liner that fits the use of a hiker or backpacker, each has specific benefits and drawbacks that may make you choose to purchase or avoid them based on the climate and other needs of the thru-hike.

Merino Wool Liners

Let’s face it merino is amazing, it keeps you warm when wet, cool when hot, and just generally amazing next to the skin. It also doesn’t stink when you sweat (a lot). So a liner made of merino wool would be perfect for multi-day hikes in any environment.

Silk Liners

Silk feels amazing and cool and helps you sleep but is expensive and doesn’t provide much warmth on its own. It also loses some insulating properties when it gets wet, though it will dry quickly.

Fleece Liners

Using fleece is a great way to get some extra warmth at a much lower cost. It also dries quickly if it gets wet and doesn’t lose any insulation when wet. The only downside is that fleece can be heavy and bulky.

Synthetic Liners

Synthetic liners are an excellent way to save on weight and can insulate when wet without losing insulation. They also dry very quickly, which is great in the event that you get caught in a rainstorm. However, synthetic fibers tend to retain heat more than natural fibers do when used for liners at colder temperatures.

Cotton Liners

One of the worst materials on the trail itself isn’t a bad choice for comfort in a sleeping bag liner. It will keep you warm and isn’t as bulky as other materials but it doesn’t dry quickly and it retains moisture so it can be heavy when wet.

Blended Fabric Liners

These would be the blends you see at an outdoor store like REI where they have 50% synthetic and 50% natural fiber. This gives some of the benefits of each material while minimizing the overall drawbacks.

Our Guide to Help Choose Your Sleeping Bag Liner

There are a few things we can go over that can help you make the right choice when trying to find the right one, so the question is, how do you pick a sleeping bag liner?

Purpose

Why are you wanting to bring the liner, are you wanting it to make your clean-up in town easier, or are you looking to pad out the warmth of a backpacking quilt or sleeping bag that is rated for warmer temperatures?

Finding the right liner is based on the overall reason for its use. You need to start with your “why” as to add the gear, this could be a very good thing to start at the coldest time with a 30-40 degree bag/quilt and a reactor liner which can give you up to 25 more degrees of warmth for example,

Weight & Packability

If you are looking to go ultralight, weight is one of the most important things you should be looking at when it comes to buying a liner. If you just need something simple then this shouldn’t be an issue but if you want something that provides a lot of warmth, it might be a bit more cumbersome.

Climate

If you are hiking in a cold environment, then you want to make sure that the liner you choose is made of a material that will provide insulation. If you are hiking in a hot climate, you will want to choose a liner made of a material that will help keep you cool.

Material

There are a wide variety of materials that can be used to make sleeping bag liners, each has its own pros and cons which you should consider when making the purchase.

Cotton: Cotton is a material that provides great insulation but can retain heat so it doesn’t work well in hot weather. It takes a lot of effort to dry if it gets wet, so this type may not be the best option if you are hiking in a wet climate.

Merino Wool: Merino wool is a great choice for hikers because it is lightweight, breathable, and provides insulation when wet. It also doesn’t have an odor, which is a plus.

Fleece: Fleece is a good choice for insulation and can be very lightweight. It does not provide as much warmth as some of the other materials listed but it is less expensive and dries quickly if it gets wet.

Synthetic: Synthetic materials are often used because they are lightweight and provide insulation when wet. They also dry quickly, which is perfect for those who tend to get caught in rainstorms. However, they can often retain heat, so this material isn’t a good choice for hikers who need to keep cool.

Silk: Silk is a natural fabric that is lightweight and makes excellent liners but it can be expensive and may not insulate well when wet.

Shape or Cut

You can choose from the two main shapes which are mummy and regular. Mummy-shaped sleeping bag liners are tapered so they can fit snugly around a mummy sleeping bag and regular-shaped sleeping bag liners are not tapered.

Price

The cost will vary a lot depending on the material, shape, and nearly everything above can influence the cost higher or lower.

Final Thoughts on Sleeping Bag Liners

Sleeping bag liners can be a great addition to your backpacking kit. They are lightweight, easy to pack, and provide additional insulation that may come in handy on those cold nights when you’re trying to stay warm as possible without adding more weight or bulkiness.

The type of liner you choose will depend on the reason for getting one, whether it’s for clean-up after hiking or padding out a sleeping bag with less warmth. You also need to consider what climate zone you’ll be exploring so the material is best suited for your needs too.

If you would like to look at what I think are the top options for a thru-hiking shelter take a look at it here, if you are interested in looking into other gear I have a page with nearly all the gear options here.