Do Sleeping Bag Liners Work? Which Are Warmest?

Last Updated on 06/03/2022

Do Sleeping Bag Liners Work

Do Sleeping Bag Liners Work?

We all want to add a few degrees of warmth to our sleeping bags, but do sleeping bag liners work? In short, yes. Sleeping bag liners are not just an effective way to sleep a bit warmer but are also a great way to keep your sleeping bag clean and stay safer in hostels or hotels. In this article, we explain everything you need to know about how sleeping bag liners work.

When winter rolls around each year, we pack away our summer sleeping bags and dig out our winter alternatives. Usually, this decision is made after a few nights away where you realize your summer bag is no longer up to the task of fending off cold fall nights.

If you’ve got a full winter sleeping bag, chances are it’s far too warm, or bulky, to want to use it any sooner than you have to. A quality sleeping bag liner can get you a few more nights out of your summer bag or even turn your 3-season bag into a winter choice.

Sleeping bag liners are an essential travel item, too. If you plan to stay in a hostel, especially in a developing nation, liners will give you real peace of mind at night. Not only do they keep you warm, but can help you avoid picking up illnesses and bugs.

What are Sleeping Bag Liners Used For

There are lots of reasons to use a sleeping bag liner and almost no downsides. Here are some of the benefits to using a liner inside your sleeping bag:


A quality sleeping bag liner will add extra insulation to your sleeping bag and is the main reason people choose to use them. Think of it as wearing a base layer under your normal clothing. Of course, with different materials, you get different levels of insulation and we will look at this shortly.

Sleeping Bag Hygiene

A sleeping bag liner helps keep your sleeping bag clean. If you climb into your sleeping bag after a long day on the trail, you’re taking in all that sweat and grime that you’ve built up. A sleeping bag liner protects your sleeping bag from, well, you. If you wear pajamas then this isn’t such a problem but if you sleep in your underwear or naked then a liner is almost essential.

Easy to Wash

Sleeping bag liners can also be put through the wash much easier than a sleeping bag. Washing a sleeping bag, especially a down-filled bag, requires specific cleaning products and plenty of room to wash and dry your bag. Down in unwashed sleeping bags used without a liner can clump and become less effective at keeping you warm.


In short, sleeping bag liners are highly comfortable. Whether you’re in your sleeping bag or in a hostel, a sleeping bag liner is comfortable against your skin while you sleep. They are worth their weight and take up very little space in your pack. In hot countries, sleeping bag liners are often more comfortable to sleep in than a sleeping bag.

Types of Sleeping Bag Liner Material

You can get sleeping bag liners in lots of different materials and everyone will have their own preference but Thermolite and CoolMax are possible the best choices on opposite ends of the spectrum. Here are the different types of material used for sleeping bag liners:


By far the most affordable liner material is cotton. Cotton sleeping bag liners are lightweight and pack down relatively small, but don’t offer much in the way of warmth. These are a good option for those on a budget or traveling to warm countries.


Silk is an incredibly lightweight and packable option that is extremely soft on your skin. It balances warmth against comfort and pack size but is more useful for keeping a sleeping bag clean than adding many degrees of warmth. Silk is one of the best options for backpacking hostels as its tight weave helps prevent bed bug bites.


Synthetic sleeping bag liners, usually some form of fleece, can easily be the difference between a chilly or a comfortable night’s sleep. These synthetic liners are warm but often end up quite bulky, especially the cheaper options. Sometimes, it feels as though you may as well have carried an extra sleeping bag.


If you want warmth without the bulk, thermolite from Sea to Summit is warm, without the weight. A lightweight thermolite liner can add up to 14°F of warmth to your sleeping bag and weighs just 8.7 oz. Thermolite liners can also be used as a standalone sleeping system in hot climates, too. We will look at this shortly.


If you’re traveling to a hot or humid area, the Sea to Summit Coolmax sleeping bag liners will wick away moisture to help keep you cool overnight. If you are traveling to or camping in countries where nighttime temperatures don’t drop below 80 degrees then this is a feature you should prioritize. These liners also dry quickly, so you can wash them almost daily while you travel.

Sea to Summit Thermlite Reactor Fleece Sleeping Bag Liner

What is the Warmest Sleeping Bag Liner?

There are a number of sleeping bag liners on the market which claim to add at least a season’s warmth to your bag. Mostly, these are fleece liners. Many of these weigh in at almost a kilogram and can add almost as much bulk to your pack as carrying another sleeping bag.

While these may be suitable for car camping, if you want a warm liner that you can carry with you, the Sea to Summit Thermolite liner series is our top choice. The Sea to Summit Reactor Extreme adds an enormous 25°F and weighs just 14 oz which is basically what a summer sleeping bag offers. If you combine this with any sleeping bag you will no doubt stay toasty warm at night.

Can You Use a Sleeping Bag Liner On Its Own?

Yes. In warm environments and especially in the summer, a sleeping bag liner alone may trap more than enough heat to keep you comfortable overnight. In fact, Thermolite liners are designed to be able to be used on their own.

Sleeping with just a sleeping bag liner can be extremely comfortable. They’re highly breathable and give you plenty of movement.

If you’re confident you won’t need a sleeping bag, this can also save you loads of pack space. Don’t get caught out, though, if temperatures do drop lower than you anticipate.

What Temperatures Do Sleeping Bag Liners Work Alone At?

If you sleep in appropriate baselayers, a sleeping bag liner alone can work down to reasonably cool temperatures. The Sea to Summit Reactors, their thermolite series, is again our top choice if you want to use a liner as a standalone bag.

The Reactor will keep you comfortable down to temperatures around 55°F, while the Reactor Extreme can go all the way down to 50°F.

Do Sleeping Bag Liners Work for Bed Bugs?

When you’re staying in hostels, especially in developing countries, bed bugs are a real concern. But do sleeping bag liners work to prevent bed bugs? Nothing is guaranteed to prevent bed bugs, but a sleeping bag liner will give you extra protection against being bitten.

Silk liners are especially good for this, as their tight weave is more difficult for the bugs to penetrate. If you use a sleeping bag liner to protect yourself from bed bugs I would say you are better off with one than without.

Are Sleeping Bag Liners Worth it?

In short, yes. Sleeping bag liners are often overlooked as an unnecessary expense when you’re buying your camping kit. A good liner will keep you warmer and make the process of cleaning your sleeping bag far easier. A clean sleeping bag lasts far longer and is not just much nicer to sleep in, but warmer, too.

Liners can keep you safer and warmer while traveling and mean you always have a layer of protection from the elements. These lightweight, affordable pieces of equipment can make all the difference. Everyone who goes camping should invest in a quality sleeping bag liner.


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This article has been written and/or edited by Andrew N. 20+ years of hiking, mountaineering, and camping experience, with access to all the latest outdoor gear.

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