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The best sleeping bag liners are one of the cheapest ways to sleep warmer, keep your bag clean and stretch one sleeping bag across more seasons. A liner slips inside your bag like a sheet. Depending on the fabric, it can add a few degrees or a lot of warmth, absorb the sweat and body oils that slowly ruin insulation, and double as a light summer sleeping bag or a clean sheet in a hostel. Our guide on how to stay warm in a sleeping bag explains where a liner fits in the bigger picture.
We checked six popular liners on Amazon for rating, stock and real specifications, from a premium thermal liner to a silk travel liner and budget fleece and velvet options. If your bag itself is the problem, our list of the best backpacking sleeping bags is the place to start.
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What the Best Sleeping Bag Liners Actually Do
A liner does three jobs. First, warmth: it adds a layer of insulation inside the bag and traps a thin layer of warm air against your body. Second, hygiene: it catches sweat, skin oils and dirt that would otherwise work into your sleeping bag’s insulation, and you can wash a liner far more easily than a bag. Third, versatility: on warm nights you can sleep in the liner alone on top of the bag, and when traveling it serves as a clean sheet in huts, hostels and guest beds.
Be realistic about warmth claims. Manufacturers measure the extra warmth in ideal conditions, and real world gains are usually smaller. A silk liner might add a few degrees, a thermal knit liner a noticeable amount more, and fleece the most. Still, for the price of a dinner out, a liner can turn a chilly night into a comfortable one.
The Best Sleeping Bag Liners at a Glance
| Liner | Best For | Material | Shape | Rating |
|---|---|---|---|---|
| Sea to Summit Reactor | Best overall | Thermolite Pro knit | Mummy | 4.6 (110+) |
| Litume Thermal Liner | Best budget thermal | Thermolite | Mummy | 4.4 (350+) |
| Litume Fleece Liner | Warmest | Fleece | Mummy with hood | 4.6 (800+) |
| Litume Velvet Liner | Best for cool nights | Velour fleece | Mummy with hood | 4.4 (320+) |
| COCOON Silk MummyLiner | Best lightweight | Silk | Mummy | 4.3 (190+) |
| Frelaxy Ultralight Liner | Best for travel | Lightweight synthetic | Rectangular | 4.3 (250+) |
Our Six Liner Picks in Detail
Each pick links to its current Amazon listing. Several come in more than one size or shape, so check the options on the listing before you order.
Sea to Summit Reactor: Best Overall
The Reactor is the liner most backpackers recommend, and it is the one to buy if you want real warmth without much weight or bulk. It uses Thermolite Pro, a knitted fabric made from hollow core fibers with ceramic pigments designed to reflect body heat back toward you. The knit stretches with you, so it never feels like you are wrapped in a sheet.
A drawcord footbox can be opened for airflow or closed for warmth, and HeiQ Fresh odor control keeps it from smelling after long trips. Its mummy shape fits inside almost any bag, and Sea to Summit backs it with its own guarantee.
Specs That Matter
- Material: Thermolite Pro knit
- Shape: mummy with drawcord footbox
- Odor control: HeiQ Fresh
- Use: three season bags in colder weather
Who It Is For
Backpackers who want to push a three season bag into late fall and early spring without carrying a heavier bag.
Litume Thermal Liner: Best Budget Thermal
Litume’s thermal liner uses the same family of Thermolite insulation as pricier liners at a lower price. The brand claims up to 22 degrees Fahrenheit of added warmth, which is optimistic in the real world, but it adds a genuine boost to a summer or three season bag.
It has a durable 70D nylon shell, compresses into a small stuff sack, and skips the zipper entirely, so there is nothing to snag or press against you at night. With more than 350 ratings at 4.4 stars, it is a proven budget option.
Specs That Matter
- Material: Thermolite with 70D nylon
- Shape: zipperless mummy
- Claimed warmth: up to 22F
- Pack: compresses small
Who It Is For
Campers on a budget who want a thermal boost for cool nights and do not need the lightest possible option.
Litume Fleece Liner: Warmest
If maximum warmth matters more than weight, fleece is the answer. Litume’s fleece mummy liner uses thick, soft fleece that feels like a cozy blanket, and the brand claims up to 27 degrees Fahrenheit of added warmth. It has a drawstring hood that wraps around your head and shoulders.
At about 1.1 pounds, it is too heavy for ultralight backpacking, but for car camping, cabins and winter trips where weight matters less, it is an excellent way to sleep warmer. It packs into an included stuff sack and is the most popular liner on this list, with more than 800 ratings.
Specs That Matter
- Material: thick fleece
- Weight: about 1.1 lb
- Shape: mummy with drawstring hood
- Claimed warmth: up to 27F
Who It Is For
Car campers, winter campers and cold sleepers who want the biggest warmth boost for the money.
Litume Velvet Liner: Best for Cool Nights
The velvet version sits between Litume’s thermal and fleece liners. Its velour fleece is soft and breathable, made without intentionally added PFAS, and the brand claims up to 14 degrees Fahrenheit of added warmth, a sensible boost for spring and fall nights.
It has a mummy shape with a drawstring hood and cord lock, dries quickly, and comes with a 70D nylon stuff sack with a strap. It is a good pick for people who want something cozier than silk without the bulk of full fleece.
Specs That Matter
- Material: velour fleece, PFAS free
- Shape: mummy with hood and cord lock
- Claimed warmth: up to 14F
- Care: quick drying
Who It Is For
Spring and fall campers, and anyone who finds silk too thin but fleece too heavy.
COCOON Silk MummyLiner: Best Lightweight
Silk is the classic liner fabric for good reason. It is very light, packs down smaller than almost anything else, feels smooth against the skin and breathes well. COCOON’s MummyLiner tapers to match a mummy bag, so there is little excess fabric to bunch up.
Silk adds less warmth than thermal or fleece, but it keeps your bag clean, adds a few degrees and works year round. It is also a favorite for travelers who want a clean layer between themselves and hostel or hut bedding.
Specs That Matter
- Material: silk
- Shape: mummy, tapered foot
- Weight: very light
- Use: hygiene, light warmth, travel
Who It Is For
Ultralight backpackers, thru hikers and international travelers who want a clean, packable layer.