Sleeping Bag Not Warm Enough? The 6 Warmest Sleeping Bag Liners for 2021

Disclosure: This post contains affiliate links, meaning that we earn a commission if you purchase a product or service through our exclusive links, at no cost to you. For more details, please read our full disclosure.

If you love camping as much as I do, it makes sense to invest in a good quality sleeping bag. After all, you need something that will not only let you sleep in comfort beneath the stars, but will also last for several years. The problem is that not all camping happens under the same conditions. Depending on where you live or the time of year you go camping, you will need different levels of warmth from your sleeping bag.

Instead of investing in more than one bag, your best bet is to purchase a sleeping bag liner. The best sleeping bag liners are a must-have when camping. They will improve the warmth of your sleeping bag, while adding to the comfort and keeping it clean. So, if you’re looking for a thermal sleeping bag liner, look no further. Here are 6 of the warmest sleeping bag liners we could find.

What Is a Sleeping Bag Liner? 

A sleeping bag liner is like a bedsheet for your sleeping bag, while serving several purposes. You can buy them in a variety of fabrics, including silk, cotton, and polyester blends. As you’ll see below, each material has its benefits.

Sleeping Bag Liner Prices

I mentioned that a sleeping bag liner is like the sheets on your bed. The same could be said for sleeping bag liner prices. Similar to bed sheets, you can expect to pay anywhere from $25 to over $100, depending on the type of fabric and the quality of the overall product. Of course, there’s less material in a sleeping bag liner than a bedsheet set, so you could say that liners are more expensive.  

Benefits of Using a Sleeping Bag Liner

For the purpose of this article, we’re rating sleeping bag liners based on their ability to keep you warm while you’re sleeping under the stars. But they do more than just keep you warm. Here are some of the other benefits of sleeping bag liners: 

Comfort

A sleeping bag liner will make just about any sleeping bag more comfortable, as they tend to have a more natural feel to the fabric. Generally speaking, silk sleeping bag liners feel the best, although cotton liners can be soft and cool also. 

Cleanliness 

A sleeping bag liner makes it a lot easier to keep the bag clean, which means you won’t have to wash it nearly as often. Instead, throw the sleeping bag liner in the washing machine when you return from camping, and you’re good to go. Remember, your sleeping bag is a lot more valuable than the liner, so make it last by keeping it free of dirt, oils, and odors. 

Flexibility

Depending upon where you live, you may go camping in different weather conditions, from cool nights in the spring and fall, to extreme heat during mid-summer. A sleeping bag liner can be added when extra warmth is needed or removed when the nights are too hot. If it’s hot enough, you might want to ditch the sleeping bag altogether and just use the liner. 

Warmth

One of the main reasons campers buy sleeping bag liners is for the extra warmth. Even during the summer months, the nights can get cool when you’re sleeping in a tent, under the stars. While the amount of warmth a liner adds depends a lot on the material, a warm liner can add as much as 25 degrees of warmth to your sleeping bag. 

A Caveat About Warmth Rating Claims

Many sleeping bag liner manufacturers will provide a temperature rating. For example, they may claim that their liner adds 10°F of warmth to a sleeping bag. While these ratings are sometimes accurate, they are not a guarantee, and when you read the product reviews, you often find conflicting opinions on whether temperature rating is in fact accurate.

Generally speaking, the heavier the liner, the warmer it’s going to be. Fleece or microfiber will b warmer than silk or a poly-cotton blend, which is why you won’t see the latter materials featured in this article.

Warmest Sleeping Bag Liners 

Now that we’ve covered the basics on sleeping bag liners, here’s our list of the warmest ones we’ve found for 2021. 

REDCAMP Fleece Sleeping Bag Liner 

The REDCAMP fleece sleeping bag liner is rectangular in shape and made of thick, breathable fleece material, so much so that it could double as a fleece blanket if needed. According to the manufacturer, it adds about 68°F of warmth to your sleeping bag.

It’s a full 75″ in length when rolled out, more than long enough for someone over 6 feet tall. If you and your partner use a double sleeping bag, you can purchase two of these liners and easily zip them together. It’s also machine washable.

What We Like:

  • Very warm, can be unzipped and used as a fleece blanket
  • 75″ long for tall people
  • can be combined with an extra-liner for double sleeping bags
  • machine washable

Dimensions:

  • 75″ length x 31″ width (190cmx78cm)
  • 800 grams
  • Available in blue and grey

Hotcore Thermal Fleece Sleeping Bag Liners Fleece Blanket (Mummy)

This Hotcore thermal fleece sleeping bag liner is the perfect shape for your mummy-style sleeping bag (it’s also available in a rectangular shape.) It’s rated to add 10°C of warmth, so it’s not as warm as thicker fleece liners, but perfect if you live in a warmer climate. On the plus side, at less than a pound it’s super lightweight, perfect for a backpacking trip, and boasts extra length for taller campers (78″).

What We Like:

  • Thin fleece liner adds just enough warmth
  • 78″ length is ideal for tall campers
  • Comes in mummy and rectangular shapes

Dimensions:

  • 78″Lx 31″W x 17.5″B (200 x 80 x 45 cm)
  • 360 grams carrying weight
  • Rated for 10°C warmth

FE Active Fleece Sleeping Bag Liner

The FE Active fleece sleeping bag liner is made of thicker fleece material for added warmth. This makes for a heavier carrying weight of just under 2 pounds. It comes with a hood and a dual-slide zipper that can be opened and closed from the inside or outside. It’s a fairly standard length (74.5″), lo enough for most campers, while the hood adds an additional 11 inches. This liner is a reasonable alternative to the REDCAMP model featured above, with the unique feature of a smooth, polyester outer shell.

What We Like:

  • Thick fleece material
  • Includes a hood for added length and warmth
  • Dual-slide zipper
  • Outside of liner made of smooth polyester

Dimensions:

  • 85.3″ long (including hood) X 30.5″ wide
  • Carrying weight of 862 grams

Sea to Summit Thermolite Reactor Extreme Sleeping Bag Liner

When it comes to choosing a sleeping bag liner for extra warmth, the Sea to Summit Thermolite Reactor Extreme might be the gold standard. It combines a super warm rating of 25°F with an ultralight Thermolite material. This sleeping bag liner is only 227 grams, well under one pound. One thing to note, however, it doesn’t have a zipper. It’s a sleeping bag insert.

What We Like:

  • Extra warm 25°F rating
  • lightweight material
  • built-in hood

Dimensions:

  • 82″X 35″ X .40″ (210.82 x 88.9 x 1.02 cm)
  • 227 grams

Osage River Microfiber Fleece Zippered Sleeping Bag Liner

This sleeping bag liner from Osage River claims to add a whopping 55°F of warmth. While this is hard to believe, there’s no doubt that this soft microfiber fleece makes a great sleeping bag liner for winter. It’s of medium weight, at 544 grams. It’s well-suited for campers of an average height, but the 70″ total length might not be long enough for anyone approaching six feet or more. This sleeping bag liner does not have a hood. If you can work with the dimensions and are looking for a warm liner, it’s certainly worth a look.

What We Like:

  • suitable for average-sized campers
  • Microfiber fleece adds plenty of warmth
  • Compact-size
  • Not too heavy

Dimensions:

  • 70″ X 31″
  • 544 grams

TOBWOLF Microfiber Sleeping Bag Liner

This microfiber sleeping bag liner from TOBWOLF is the heaviest on our list, weighing in at 998 grams. That said, if adding extra warmth to your sleeping bag is your priority, chances are you won’t mind the extra weight. I like that it unzips and can also be used as a soft, microfiber blanket. It’s got plenty of length at 87″ when you include the hood, and 75″ without. Like the other bag liners on this list, it can be easily rolled up into the included drawstring pouch for easy transport.

What We Like:

  • soft microfiber fabric
  • unzips for use as a blanket
  • Ideal for taller people

Dimensions:

  • 87″ X 30″ (220 X 75cm)
  • 998 grams

What Is the Best Sleeping Bag Liner for Warmth?

Now that you’ve read through our full sleeping bag liner review, you may be wondering which one is right for you. While the Osage River or REDCAMP liners might be the warmest overall, the Sea to Summit Thermolite Reactor Extreme Sleeping Bag Liner is our choice as the best all-round sleeping bag liner for extra warmth, because you get an impressive 25°F temperature rating at a weight of only 227 grams. When you factor in the built-in hood and its overall length, it’s the one we recommend.

Leave a Comment