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What’s up with Sleeping Bag Liners?

Last Updated on June 11, 2016 by mountainswithmegan

It looks pretty, but it gets cold at night.
It looks pretty, but it gets cold at night.

This past fall, I was going into the Great Sand Dunes National Park to work for two months. Temperatures were expected to be very cold at night. My crew leaders recommended a 0 degree sleeping bag. The warmest bag I had was 20 degrees, and I wasn’t about to go buy a new one for a job that wasn’t paying much. That would defeat the purpose of working.

I resigned myself to sleeping in multiple layers of clothing at night. My roommate offered to let me borrow his sleeping bag liner to give it a try. I didn’t know how much it would actually help, but it wasn’t very heavy so I figured I would try it out.

To my surprise, the liner actually added a decent amount of warmth to my bag. I could definitely tell the difference from when I used it and I when I didn’t have it.

There are a lot of mixed reviews about sleeping bag liners. I have heard people say they don’t really add extra warmth or they are a waste of weight. I also know people who overly dramatize the benefits of sleeping bag liners. I’m somewhere in the middle. I like having them to add a little extra heat to my bag, but I don’t really think they’re as warm as they are advertised to be.

I have a Sea to Summit Reactor Thermolite Mummy Bag Liner (it’s a mouthful, I know). Overall, I’m pretty happy with it. I don’t think it adds the full 15 degrees that it advertises, but I think it does add an extra 10 degrees, although it’s hard to say for sure since it’s difficult to measure such a thing. It feels like an extra 10 degrees though.


Sleeping Bag Liner Pros:

  • It gives your bag extra warmth and it’s comfortable to sleep in.
  • It keeps your bag cleaner. I get pretty dirty and sweaty while hiking, which transfers to my bag. Oils from your skin can also soak into the bag. Sleeping in a liner keeps your sleeping bag cleaner so you don’t have to wash it as often. Washing synthetic bags breaks the fibers down quicker. Washing down bags is difficult because you need a special soap for down that you are unlikely to find on the trail.
  • It can help you save money if you already have a bag. Getting a liner to supplement the bag you have is certainly cheaper than buying a new sleeping bag.


  • Like I said before, liners are usually not as warm as they are advertised.
  • It’s not a replacement for a crappy sleeping bag. If you have an over-used bag or a low-quality off brand bag, the liner won’t really help you much.
  • The warmth-to-weight ratio isn’t very good. Liners don’t really insulate. The ounces would be better used in a warmer sleeping bag.

I have seen people only using sleeping bag liners during summer months in order to save weight on carrying a bag. I personally wouldn’t do it, mainly because the weather can get cold even in the summer. Liners don’t do anything to block the wind either, so you might get cold if you ever sleep outside of your tent. This isn’t a viable option if you are a cold sleeper.

Overall, I like the additional warmth that liners provide and I think they’re a great way to extend the life of your sleeping bag, but I don’t think they are always a necessity.

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