Last Updated on 21/02/2024
Guide to Sleeping Bag Liners
If you’re going to enhance your sleeping system, you need the best sleeping bag liner available. Sleeping bag liners improve both the comfort and warmth of your sleeping system. A quality sleeping bag liner is important for good hygiene too, as you can remove it and put it through the wash.
Sleeping out through all seasons can often require you to own multiple sleeping systems. Alternatively, a quality sleeping bag liner can quickly change your summer sleeping bag into a three-season setup.
Sleeping bag liners come in various materials and in different shapes and sizes. There are sleeping bag liners to keep you cool, to keep you warm, and even those that can be used as a sleeping bag in their own right. Learn how sleeping bag liners keep you warm here.
This guide is going to look at all things sleeping bag liner, then. We’ll look at how to pick your sleeping bag liner, how to use it, and why they come in so many different options.
11 Best Sleeping Bag Liners
Sea to Summit Reactor Thermolite Liner Extreme
- MATERIAL: 100% Polyester Thermolite Extreme
- WEIGHT: 13.9 oz / 394 g
The Sea to Summit Reactor Thermolite Liner Extreme is the best sleeping bag liner in almost every single way. Most importantly, it provides the best warmth-to-weight ratio of any sleeping bag liner, aside from the down-filled Spark Ultralight which is 3 – 4 times more expensive. If it is the warmth you want, then look no further.
The comfort of this sleeping bag is next level with massive amounts of stretch and super soft material. The Reactor Series of sleeping bag liners sets the benchmark of what is possible in terms of warmth, weight, and performance. There is the fleece option also on this list, as well as two others that include a midweight option and a compact option too.
A simple but surprisingly useful feature of all Sea to Summit sleeping bag liners is that they have a strip of different colored fabric around the hood or opening. This makes it so much easier to find the hole in an enclosed space like a tent or sleeping bag. You can both see and feel where the edge is so that you can easily slip into it, which is more helpful than you might expect.
VERDICT: This really is the top-of-the-range, undisputed champ in our opinion. The price is very reasonable, and it is designed by the worlds leading sleeping bag liner experts. In summer, you can use it as a full sleeping bag on its own or add 25°F / 15°C of heat to your existing sleeping bag. You can tell how much we love this product and would recommend it to anyone.
Sea to Summit Spark Ultralight Sleeping Bag Liner
- MATERIAL: 7D lining and shell, 850 FP Ultra-Dry Down Insulation
- WEIGHT: 7.9 oz / 224 g
The Sea to Summit Spark Ultralight Sleeping Bag Liner is probably more accurately described as a summer sleeping bag rather than a liner. When used as a liner, it is best for adding warmth to sleeping bags in 0-degree temperatures. When used on its own, it is recommended for temperatures down to 50 degrees (F) or 10 degrees (C).
Using 850-fill power Ultra-Dry Down insulation gives your sleeping system extra loft, which a fabric sleeping bag liner cannot. This extra loft is perfect for trapping warm air, and so will add far more warmth to your sleeping bag than any other liner on this list. That does come at a cost, though, with the price tag being over $200.
VERDICT: The Sea to Summit Spark Ultralight Sleeping Bag Liner is an excellent way to adapt your current sleeping bag to be a lot warmer in winter. The comfort is next level thanks to the lofty down. However, there is no stretch, which can feel a little restrictive. Still, this might be your only option if you like the feeling of being wrapped in goose down.
Therm-a-Rest Sleeping Bag Liner
- MATERIAL: 100% 70D Brushed Polyester
- WEIGHT: 10 oz / 283 g
You may recognize Thermarest as a specialist in sleeping mats and pads, but they also have a small range of sleeping bags and liners, which are fairly unique in a crowded market. The Therm-a-Rest Sleeping Bag Liner is one of our favorites because it is so easy to use and is designed to fit perfectly inside any mummy sleeping bag.
The hood has a nice lip that sits just over your forehead and provides extra comfort as you close your eyes for the night. You have a half-length zip with a press stud cover that makes getting in and out of your sleeping bag and liner as easy as can be without having to feel a cold zip against your face. A toggle on the right-hand side lets you really sinch the hood in to trap maximum body heat, which is another nice feature.
VERDICT: We really weren’t expecting to like this as much as we do, but it still only adds around 5 degrees Fahrenheit of heat to your sleeping bag, which isn’t that much when there’s snow building outside. Still, we highly recommend this liner for camping and backpacking.
Sea to Summit Adaptor Coolmax Sleeping Bag Liner
- MATERIAL: 100% Polyester CoolMax
- WEIGHT: 8.7 oz / 248 g
The Sea to Summit Adaptor Coolmax is the best sleeping bag liner for summer months and hot weather. Unlike the other Sea to Summit sleeping bag liners, this one is designed to keep you cool and have enhanced moisture while you sleep. This is the ideal sleeping bag liner for backpacking around humid countries, staying in hostels and cheap hotels where you can’t trust the cleanliness of the bedsheets.
You can get an Insect Shield permethrin treatment upgrade, which is definitely worth it, in our opinion, for the small price increase. You might be wondering if the Coolmax sleeping liner adds any warmth to your sleeping bag. It does add a few degrees of warmth, but there are better options for cold climates. If you plan to use it primarily in hostels, you can get the rectangular version with a pillow insert for the best night’s sleep.
CONCLUSION: The Sea to Summit Adaptor Coolmax, sleeping bag liner, is what you need when the air is so thick and humid that you don’t want any duvet covers. The Insect Sheild option acts as the perfect barrier to creepy crawlies and mosquitos at night and provides much better coverage than bed sheets. We highly recommend this for backpackers traveling to places like Asia, South America, Africa, and Australia.
RAB Ascent Sleeping Bag Hooded Liner
- MATERIAL: 100% Silk
- WEIGHT: 4.5 oz / 127 g
The RAB Ascent Sleeping Bag Liner is a superb option for lightweight hikers and campers who appreciate well-made and well-fitted gear. The British company was founded by famous explorer Rab Carrington who was obsessed with creating the best outdoor gear after being stranded on a Patagonia expedition in 1973. You can see our review of the Rab Down Vest if you’re interested.
The mummy shape isn’t too baggy like some other liners, and the luxurious silk feels very soft on the skin. It is available in cotton as well as silk but without the hood, and we strongly believe hoods are worth having. The pack size is listed as 8 x 5 x 4 inches, but we can tell you it packs down much smaller than this if you compress it.
VERDICT: Three things that stand out about the RAB Ascent Sleeping Bag Liner are its weight, well-fitted shape, and the fact that it rarely gets twisted inside your sleeping bag. Perfect for keeping your sleeping bag clean, adding warmth, or using it on its own in the summertime. Now available in America, you are likely to start seeing more of this awesome brand.
Sea to Summit Reactor Thermolite Fleece Liner
- MATERIAL: 100% Polyester Thermolite Fleece
- WEIGHT: 14.8 oz / 420 g
The Sea to Summit Reactor Thermolite Fleece Liner is the warmest in this guide with a temperature boost of 25°F / 15°C inside your sleeping bag. The issue with fleece is that it is heavier than other materials and very bulky so you have to decide which is more important. Apart from making excellent insulation, the benefit of fleece is that it is very soft and cozy, unlike the lining of your sleeping bag, which can feel cold to the touch when you first get in.
Packing down to 6.5 x 4.5 inches is actually impressive for a fleece sleeping bag liner, so we can’t really complain about that. A quarter-length zip is a really nice feature of this model and is great for getting in and out if you need to pee at night. The moisture-wicking is good; however, it is not as good as with the hollow fiber fabrics.
VERDICT: We really like this Thermolite fleece sleeping bag liner by Sea to Summit and would be happy to use it on its own in summer or trust it to keep us warm in winter. Owning this means that you don’t need to pay hundreds of dollars for an expensive winter sleeping bag; you just combine it with what you already have and maybe wear some thermal underwear if you need to. The point is this is warm, cozy, and worth the money.
Big Agnes Wool Sleeping Bag Liner
- MATERIAL: 87% New Zealand Merino Wool, 13% Nylon
- WEIGHT: 16 oz / 454 g
The Big Agnes Wool Sleeping Bag Liner is an awesome sleeping bag liner if you appreciate the benefits of Merino wool. One of the many reasons this liner for sleeping bags is so impressive is because it has natural anti-bacterial properties that keep it cleaner and odor-free for longer. The two downsides of Merino wool sleeping bag liners are that they are expensive and heavy in comparison to synthetic options.
If you like the design and Big Agnes as a company but don’t fancy the Merino liner, then they do also have a cotton version that feels like soft bed sheets. The compromise you make with cotton is that it does not typically handle moisture very well. In terms of what’s available, though, this is the best wool sleeping bag liner out there.
VERDICT: As big fans of merino wool, we like this sleeping bag liner for long trips and hikes where you might not get a chance to wash your gear too often. Four little hooks around the outside secure your liner in position and prevent the dreaded twist. Overall, there are better value options out there, but none are as cool as wrapping yourself in wool for New Zealand mountain sheep.
Sea to Summit Premium Silk Sleeping Bag Liner
- MATERIAL: 100% Premium Ripstop Silk
- WEIGHT: 4.8 oz / 136 g
The Sea to Summit Premium Silk Sleeping Bag Liner is perfect for travelers who want the extra comfort and texture of silk against their skin. It is possibly the best silk sleeping bag liner out there and features two spandex panels along the side for flexibility. Available in a range of colors, shapes, sizes, hooded options, and pillow inserts, it also has a double version available for couples.
While this liner doesn’t add a massive amount of heat to your sleeping bag, it does increase the warmth by a few degrees. The real benefit is in the next-to-skin comfort, which is ideal for backpacks, staying in hostels, and couch surfing. You can get a size to fit any sleeping bag with different lengths and shapes available – rectangle and mummy.
VERDICT: The Sea to Summit Premium Silk Sleeping Bag Liner is a luxurious piece of camping gear that is designed to withstand the trail. The ripstop silk is both amazingly soft and durable at the same time. The weight and compact size make it ideal for lightweight hikers and backpackers. Just don’t expect it to add too much warmth.
Western Mountaineering Tioga Sleep Liner
- MATERIAL: 100% Silk
- WEIGHT: 3.6 oz / 103 g
The Western Mountaineering Tioga Sleep Liner is the most lightweight sleeping bag liner in this guide and also the most compact. This makes it well suited to travelers and campers with limited backpack space who want the extra comfort, protection, and warmth that a liner offers. Western mountaineering makes excellent sleeping bags, and this is the perfect accessory to help keep your expenses down. The sleeping bag is clean with maximum loft.
Western Mountaineering also makes another sleeping bag liner in a 100% polyester version, which is maybe a little warmer. The claimed warmth this liner brings is 5 degrees F which isn’t much, so don’t expect this to instantly turn a crappy sleeping bag into a Cypress Gore WindStopper!
VERDICT: If your main concern is keeping your sleeping bag clean and taking care of it as much as possible, then we would recommend silk for its smooth and frictionless texture. Another reason to get the Tioga Sleep Liner is that it weighs next to nothing and is well worth packing, even if you don’t use it every time. It’s not the warmest, but it still adds a lot of value.
Litume Thermolite All Season Sleeping Bag Liner
- MATERIAL: 100% Polyester Thermolite
- WEIGHT: 18.3 oz 520 g
The Litume Thermolite All Season Sleeping Bag Liner is one of the most underrated and unheard-of options on this list. Litume started as a small family business and has been slowly building an inventory of high-performance outdoor gear. Their sleeping bags and liners are especially good, and this is just one of four sleeping bag liners that they offer.
This is the Thermolite model, which can add up to 22°F / 12°C to your sleeping bag, while the fleece liner is even warmer. Thermolite uses hollow fiber technology to trap more warm air and increase moisture wicking. It is the same type of material that is used in many of the Sea to Summit Reactor series, which is super soft and stretchy.
VERDICT: The Litume Thermolite All Season Sleeping Bag Liner is an excellent choice for adding warmth and comfort to your sleeping bag. We like how tight it sinches around your face, which is perfect for wintertime when the air is freezing your cheeks off. The well-defined and unique foot box area really helps keep everything in position and untwisted, which is nice.
Snugpak Thermalon Liner
- MATERIAL: 100% Polyester
- WEIGHT: 16 oz / 454 g
The Snugpak Thermalon Liner is another great sleeping bag liner that has a good warmth-to-weight ratio for year-round use. You can get other materials like fleece, which is amazingly soft, warm, and comfortable but almost twice as heavy. Snugpak is another veteran company that serves the military with all kinds of camping equipment.
If you are over 6 feet tall and like lots of legroom, then this might be for you as the taper towards the foot box is very subtle. For other people, this can cause the issue of bunching up in the foot box, which surely adds warmth to your feet.
VERDICT: This is a highly durable sleeping bag liner for adding warmth and keeping your sleeping bag clean. Better for tall people than short people, we would say, and we wish it had a hood like the fleece option, otherwise a very high scorer.
How to Find the Best Sleeping Bag Liner
But what makes a sleeping bag liner the best one for you?
We’ll look at this in more detail later on, but sleeping bag liners come in a range of different materials. Each of these materials has its own benefits and drawbacks. The main materials are silk, cotton, fleece, microfiber, and synthetic.
Depending on your needs, some of these materials are best suited to moving fast and lightweight, while others are bulky but warm.
All manufacturers have temperature ratings on their sleeping bag liners. Unlike a winter sleeping bag, which has temperature ratings based on appropriate temperatures for their use, liners will usually have a + symbol before their rating. This rating is the degree of warmth that the liner should add to your system.
A more simplistic guide is the R-value for warmth. This r-value measures the item’s ability to resist heat flow through it. An item with a higher R-value offers greater insulation and is, therefore, warmer.
Size and Shape
Sleeping bag liners come in square or mummy-shaped, similar to sleeping bags. The best choice is to get a sleeping bag liner that matches the shape of the bag itself. This counts for size, too, as a sleeping bag liner too short or too long will be less effective.
Weight and Pack Size
This is a question you should ask yourself for every piece of equipment you buy. Do you want to carry your equipment long distances on a trek, or are you car camping, and the bulk won’t matter?
Weight and pack size often have to be balanced against attributes such as warmth. There will most likely have to be some compromise, either on warmth, weight, or cost.
No matter how warm your sleeping system is, if you are losing heat from your head, you are going to have a cold night camping. Most sleeping bags have a hood, but if you’re going for extra warmth in your sleeping bag, why not in the hood, too?
Cinching the neck of your sleeping bag prevents warmth from leaving through the gap. If you can do the same with your sleeping bag liner, it will help to increase the ability to trap warm air.
A word of caution with drawcords, though. If you pull them too tight, or if your drawcord gets caught up on your arm, you can find yourself tangled in a sleeping bag that’s too tight.
Different Types of Sleeping Bag Liner
We talked about these a little earlier, but we’re going to look at the different materials for sleeping bag liners.
Silk liners are the lightest weight on the market. They add warmth to your setup in cool weather but are also breathable and cool in the warmth. Silk liners are popular for tourists who want to avoid sleeping in dodgy hostel beds without protection.
Cotton is the most affordable option for sleeping bag liners. Cotton liners are durable and comfortable enough, and they breathe well in warm, dry weather. Though it’s not the lightest or warmest, cotton liners do a good enough job and are an easy addition to any sleeping setup.
Fleece adds a good level of warmth to your setup but is not without its bulk. Fleece liners breathe well enough, but not as well as synthetic options, in damp conditions. These liners are highly comfortable and usually the most affordable way to add proper insulation to your sleeping bag.
Microfiber sleeping bag liners are a tighter weave than cotton or silk. These can add similar warmth levels to lightweight fleece but without the same level of bulk you would have to carry.
Microfiber sleeping bag liners have limited breathability. They do dry quickly, though, so travelers can wash them regularly on the trail.
Synthetic materials balance high levels of warmth against high breathability. These are also the best warmth to weight available on the market.
Thermolite liners, for example, can easily add up to 20° to your setup while weighing less than 300 g.
Is it Worth Getting a Sleeping Bag Liner?
Sleeping bag liners are a valuable addition to your sleeping setup that is often overlooked. Read our article here for a full rundown of how effective they are.
In short, though, sleeping bag liners are highly effective. They can add warmth without upgrading your sleeping bag and keep you dry in sweaty conditions.
Most importantly, perhaps, you can easily wash your sleeping bag liner. This will help maintain your sleeping bag, as well as your friendships with fellow campers.
What Kind of Sleeping Bag Liner is Best?
The best sleeping bag liner for you will depend largely on your particular needs. The highest quality is widely recognized as the Thermolite series, from Sea to Summit. These offer great levels of warmth without excess bulk or weight.
Silk is the most comfortable sleeping bag liner material and is excellent for traveling or summer camping. It also packs down far smaller than most other liners.
Cotton or fleece are the best budget sleeping bag liners. These have more bulk than other liners but will do a good enough job if you don’t want to spend too much money.
Can You Use a Sleeping Bag Liner as A Sleeping Bag?
In hot and humid climates, you can and should use a sleeping bag liner as a sleeping bag. In places like Thailand and South East Asia, a sleeping bag liner will provide protection against insects and just enough coverage so that you don’t feel cold but also don’t overheat and sweat all night. A sleeping bag liner is much more compact and lightweight than a sleeping bag so that you can pack one in even the smallest or jam-packed backpack.
If the temperature drops on a night below 20ºC, a sleeping bag liner will not be enough to keep you warm if you sleep outside in a tent or camping in a hammock. Some of the warmest liners for sleeping bags can add as much as 8 degrees of heat so if you just want a thin layer, you should look at silk.
How Much Warmer Does a Sleeping Bag Liner Make it?
The extra warmth from your sleeping bag liner will depend mainly on the material. If adding warmth is your primary aim, then some of the synthetic models are the best sleeping bag liners for you.
As an example, the Sea to Summit Thermolite series, widely regarded as the best sleeping bag liners for warmth, adds between 14° – 32°. These four models vary in weight and bulk. They can also be used as standalone sleeping systems if the weather allows.