Best Sleeping Bag Liners to Keep You Warm at Night

If you’re in a rush and want to find out what the best sleeping bag liner is, we recommend the Sea to Summit Thermolite liner.

We all know that camping doesn’t usually provide the most ideal conditions for restful sleep. Nights can be chilly, even in the summer, and while sleeping bags do a good job at keeping us warm most of the time, they don’t always block the cold as much as we’d like. If you’re looking for a little something extra to keep you snug and cozy at night without breaking the bank on an expensive sleeping bag, we’ve got you covered. Let’s take a look at some of the best sleeping bag thermal liners that will keep you warm and comfortable.

In this article, we’ll be reviewing the following thermal liners:

What is it?

Sleeping bag liners do exactly what they sound like…they line your sleeping bag. Now, we aren’t talking about the actual lining of the sleeping bag itself. Thermal liners are a separate item that you can buy for your sleeping bag that serve a number of purposes. Like a cocoon, sleeping bag liners wrap around you like a silk bag, acting as a sort of bed sheet. Not only are they great for keeping you warm during the night, but they also improve the overall comfort level of your sleeping bag.


tent with sleeping bags next to tree

Liners are good all year, though the way that you use them will vary accordingly. In the winter, they make a great insulating layer to help you stay warm during the night. While you should have a sleeping bag that does a good enough job at keeping you from freezing, the liner will make sure you stay extra toasty. Something to remember is that these items are rated in degrees (for example, you may find a 14 degree liner). What this means is that when you use it, the liner allows you to sleep in temperatures 14 degrees colder than you otherwise could have. So if your sleeping bag is good down to 30 degrees, this particular product would allow you to stay comfortable down to 16 degrees. Many REI sleeping bag liners are great for getting this job done, but we’ll also take a look at some more cost effective products that you can find on Amazon as well.

In the summer, you can use the thermal liner as a stand alone item. A lot of sleeping bags can get too steamy to sleep in on a hot, summer night, so liners allow you to ditch the bag without losing all protection.


This one is important because you generally don’t want to wash your sleeping bag. The water and motion of the machine can ruin the filler of your bag, so if you want it clean, you usually have to do it by hand. This is obviously a pain to do every time you go camping, so why not save yourself the hassle by keeping your bag clean in the first place? 

Thermal liners are great because when you slide into your “bed” at night, the only thing that’s getting dirty is what you’re in direct contact with (aka, the liner). Unlike sleeping bags, liners usually are machine washable, so you can save yourself the headache of hand washing your gear. 


sleeping bags in a car

At the end of the day, your sleeping bag is the cozy little place where you want to enjoy some time off your feet and sleep. However, it’s rare to find a bag that isn’t made from synthetic material, and most outdoor clothing (if you sleep in it) is made from something similar. Nothing says “creature comfort” like the nice, manufactured texture of nylon, right? 

There are some people who aren’t bothered by this, and are willing to leave the extra gear behind, if comfort was the only deciding factor. But for many of you, sleep is something that you’ll want to enjoy, and finding the right thermal liner will help you do that. 


Liners come in a wide variety of materials, including polyester, cotton, fleece, and many more. Some are lighter than others, some feel better on sensitive skin, others are better at keeping you warm. Each have their own pros and cons, though I tend to prefer cotton and wool, as long as you don’t get cotton wet and don’t mind the steep price of wool.

Sleeping Bag Liner Reviews

Sea to Summit Thermolite Reactor Liner

  • Shape: Mummy
  • Added Warmth (F): Up to 25 degrees
  • Material: Polyester
  • Weight: 14 Ounces

Weighing in at a meager 9 ounces, this Sea to Summit Reactor liner isn’t just light, it also packs down to a smaller size than some phones. It’s a great product if you’re looking for something to give you some extra warmth at night without taking up too much space in your pack.

The mummy shape allows it to easily slide into any type of sleeping bag. Though it’s worth noting that even if you don’t have a mummy bag, it will feel like you do, since the thermal liner has the shape of one. While not as constricting as a mummy bag can be, if you don’t like that style, this liner might not be the best option for you. 

That being said, this is the warmest sleeping bag liner in our review. Considering the price and the weight, the tighter squeeze feels like a worthwhile tradeoff, in my opinion.


– Very lightweight
– Folds up into a tiny package
– 14 degree rating
– Mummy shape


– It’s a bit expensive for the overall quality
– Doesn’t seem to keep you as warm as advertised

Sea to Summit Silk Travel Liner

  • Shape: Rectangular
  • Added Warmth (F): Up to 5 degrees
  • Material: Silk
  • Weight: 5 Ounces

This Sea to Summit liner might be on the pricier side of the spectrum, but when you’re dealing with silk sleeping bag liners, it’s totally worth it. Unfortunately, it only adds a meager 5 degrees of warmth to your sleeping bag, but that can often be enough to move you from the realm of “discomfort” to “comfort.”

Either way, I would get this item purely because of how soft it is to sleep on. A stretchy silk liner versus the polyester interior of your sleeping bag? Yeah, that’s a no brainer for me. Not to mention, it’s machine washable, so you can easily clean it after it’s picked up all the dirt and sweat you tracked in with you. This will significantly extend the life of your sleeping bag, because it’s only the liner getting dirty, and not the bag itself!


– Silk is very comfortable
– Stretchy material
– Durable and ripstop
– Super lightweight
– Pillow holder included


– The carry case is way too small
– It’s a bit expensive

Sea to Summit Spark Ultralight Sleeping Bag Liner

  • Shape: Mummy
  • Added Warmth (F): 50 degrees
  • Material: Nylon/Down
  • Weight: 8 Ounces

If you’re looking for a cheap sleeping bag liner, the Sea to Summit Spark liner is definitely not going to be for you. As the most expensive product in our lineup, it’s honestly more of a sleeping bag than a liner. However, it still made this list because of how thin and lightweight it is.

At just 8 ounces, it’s actually lighter than some of the “true liners” that we mention below. Naturally, it’s pretty thin as well, so it could be stuffed inside another sleeping bag for added warmth. Not that you’ll necessarily need it, though. Filled with ultra-dry down, this liner has a temperature rating of 50 degrees, which is pretty crazy.

Since it’s already (basically) a sleeping bag, you can feel free to use it as such. Especially if you’re planning on staying in a hostel or a friend’s couch where you don’t care about staying toasty quite as much. In those cases, heat is less important than having a barrier against any germs or dirt that might exist.


– Versatile design
– Very lightweight
– Packs down to the size of a sandwich
– Quite warm for a liner
– Comfortable


– Price

Redcamp Fleece Sleeping Bag Liner

  • Shape: Rectangular
  • Added Warmth (F): N/A
  • Material: Fleece
  • Weight: 1.76 Pounds

The one and only sleeping bag liner on this list that’s made out of fleece, Redcamp’s product isn’t just attractive for its 20 degree rating, but also for the comfort this material is known for. Thick and breathable, you’ll be able to stay both warm and dry regardless of weather conditions. 

While fleece is undeniably one of the most comfortable, warmest materials a liner can be made from, it does come at the expense of added weight. Thick and heavy, it weighs almost twice as much as its competitors. It might only be a one pound difference, but that can be enough to make or break it for a lot of campers. 


– Warm and soft material
– Large size that’s good for couples
– Two liners can be zipped together to make a big blanket
– Two way zippers


– Heavy
– The zippers aren’t the best quality

Litume All Season Sleeping Bag Liner

  • Shape: Mummy
  • Added Warmth (F): 27 Degrees
  • Material: Fleece
  • Weight: 1 Pound

About as large as an iPhone X when packed away, you won’t even know you’re carrying the Litume all season liner. For being so small and light, it adds a surprising 22 degrees to your sleeping bag, which should be more than enough to keep you warm in almost any circumstance.

Soft and elastic, you might not want to wake up in the morning with how comfortable this liner is. The mummy shape is perfect for any type of sleeping bag too, so you won’t have to deal with fabric bunching up uncomfortably. Not only that, but the fabric wicks away moisture from your body to keep you warm and dry. If you start to sweat during the night, you won’t have to worry about waking up wet and chilled.  


– 27 degree rating
– Drawstring hood to prevent heat loss
– Very lightweight for a fleece liner
– Mummy design with a footbox
– 30 day money back guarantee
– Machine washable


– Not for ultralightweight backpacking

Vumos Sleeping Bag Liner

  • Shape: Rectangular
  • Added Warmth (F): N/A
  • Material: Polyester/Down
  • Weight: 0.73 Pounds

Though made entirely from polyester, the Vumos sleeping liner has a silky finish so that it feels better on your skin. Personally, I’m not a huge fan of silky material against my skin, but I know that many of you do enjoy it.

Coming in at 7 feet long, this liner can accommodate campers of any height with ease. The best part is that it comes with a full length zipper, so you can get in and out of it faster as well. If you’d like, you can even unzip it all the way and convert it into a bed sheet on warmer nights, or if you sleep on a cot or mattress. Because of the rectangular shape, it’s not really the greatest option for a mummy sleeping bag, unless you don’t mind it bunching up on the sides. However, for car campers looking to add a little comfort to their setup, it’s a great option for warmth and dirt control.


– Budget friendly
– Full length zipper
– Plenty of room for tall people
– Packs down to a small size


– Feels cheap
– Material is slippery

Cocoon Microfiber Mummy Liner

  • Shape: Mummy
  • Added Warmth (F): Up to 5 degrees
  • Material: Polyester
  • Weight: 8 Ounces

While it will only add about 5 degrees of warmth to your sleeping setup, the Cocoon microfiber mummy liner is still a product worth looking into. Because sometimes that extra little bit of heat is all you need in order to move from “bearable” to “comfortable,” which can make all the difference!

Even if the temperature rating doesn’t impress you, liners are useful for so much more than a little extra warmth. The microfiber texture on this product is a lot more comfortable to sleep on than the synthetic lining found on the inside of practically all mummy bags. Considering how lightweight it is, and how well it packs down, you’ll forget you were carrying this liner until it’s time to roll it out again for bedtime.


– Lightweight
– Packs down small
– Comfortable microfiber
– Machine washable
– Works well as a sleeping bag in hot temperatures


– Only adds 5 degrees of warmth

Why Trust US?

At Untamed Space, we’re passionate about helping you have the best camping experience possible. Our team of experts have experience camping and backpacking all over the world, allowing them to provide insightful and relevant content to guide you in your outdoor pursuits.

All of our reviews are based on a combination of firsthand experience, extensive research, and an analysis of customer feedback. We are an independent website and do not receive payments or incentives from manufacturers to promote their products, and we continuously update our content to provide new information based on product availability. Wherever you are in your journey, whatever gear you’re searching for, you can be sure to find unbiased and up-to-date reviews for all of your needs.

Final Thoughts

While not necessary in every situation, liners can mean the difference between freezing at night and being comfortable. And if you don’t plan on camping in colder temperatures, they’re nice to have anyway, since they’re easier to clean than your sleeping bag. We like the Sea to Summit Reactor liner because it’s great for any weather condition. Rated at 25 degrees, it’s the perfect thing to keep you toasty in most situations, and it packs down well so you can shove it in your backpack easily.

The mummy design keeps heat trapped better, but there’s still plenty of room to wiggle around so you won’t feel claustrophobic. It also comes with a hood drawstring to cinch it around you head to whatever tightness you would like.

In need of a comfortable sleeping bag to put your liner in? Check out these cozy, rectangular sleeping bags!

Spencer Yeomans

Spencer Yeomans

A lover of the outdoors, and especially the mountains, Spencer has always enjoyed pushing people to step outside their comfort zones. His mission is to help others get out of their homes, push their limits, and to have fun staying active in nature.

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