The versatile, multitalented sleeping bag liner – usually treated as an unnecessary extra – deserves a place in every traveller’s backpack.

Whether your goal is to add lifesaving warmth to your sleeping bag or to lengthen its life; to cocoon yourself in silk or snuggle up in soft merino wool, a liner can do all this and double up as a lightweight travel sheet for hot weather or dodgy hostels – in some cases for about £15.

Received wisdom claims a liner adds a season (around 5-7 degrees) to your sleeping bag, but that’s generous and is very dependent on material.

We would caution against relying on a liner in seriously cold conditions: it’s much safer to make sure your sleeping bag’s “comfort” limit is at least as low as the coldest weather you expect to encounter.

But if you’re a cold sleeper or just want an extra bit of comfort, the few degrees a liner – particularly a wool or fleece one – adds will make all the difference; and if the weather warms up, just remove it.

Liners can turn an ordinary sleeping bag into an extraordinary one: your cheap festival sleeping bag into silk-lined luxury. This isn’t just comfort-seeking: some sleeping bags, particularly down-filled bags, are notoriously difficult to wash.

A liner will make your bag last longer, providing an extra layer of protection from sweat and dirt, and is much easier to wash and dry if you’re on the road for a while. The cost of shipping a down bag back to its manufacturer for a proper deep clean – as you’re supposed to – is in most cases higher than the cost of many of the liners below.

Liners also come in handy when it’s too hot and humid to sleep inside a sleeping bag, but sleeping without anything to cover you isn’t an option: a silk or cotton liner is the perfect compromise, providing a layer of protection from ants and the sheets in less-than-meticulous and cheap hostels.

Whether you’re looking to add warmth or just give the bed bugs something else to chew on, here are some of the best sleeping bag liners we’ve found. We tested them in mummy-shaped bags (tapered with a hood), but most of these liners are available in a rectangular (“travel sheet”) shape as well.

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Cocoon merino wool mummy liner: £86.95, Absolute Snow

Offering serious luxury inside or outside a sleeping bag, Cocoon’s mummy liner is worth every penny of its higher price tag. Because the wool is stretchy the liner has none of that foot-confining, constrictive feeling that some silk and cotton liners can have inside the bag; it also feels gloriously soft and snuggly against your skin. Merino wool also has antibacterial properties, so this liner can go longer between washes without starting to smell or feel gross. Cocoon estimates that the liner adds a mighty 7 degrees of warmth; it made our sleeping bag noticeably warmer during our testing, as you might expect from shrouding yourself in wool. It’s bulkier and heavier than a silk liner, but for the luxury, well worth it.

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Sea to Summit silk stretch liner mummy: £70, Sea to Summit

Silk liners can sometimes feel constrictive, particularly around your feet in a mummy shape. Sea to Summit’s clever solution is to build stretchy panels into the sides. This adds a real sense of flexibility – you can sleep with your knees bent inside the liner easily. It doesn’t make a huge difference inside a zipped-up bag – because you’re already constricted – but is a great addition if you plan to use the liner as a very lightweight sleeping bag or as a travel sheet in unsavoury hostels. It adds around 2-3 degrees of warmth to the bag.

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Rab silk mummy sleeping bag liner: £55, Rab​

One of the best silk liners on the market, Rab’s mummy liner is also one of the smallest and lightest we tested, at 128g, and it packed down to smaller than the size of a pocket. There’s a slight feeling of constriction around the feet in the mummy bag liner (because the shape tapers), but the overall impression is of comfy luxury. Most down bags, including Rab’s own, are lined with a water-resistant material like Pertex to protect the delicate stuffing inside – that water-resistant lining just can’t compete with the feeling of silk on your skin.

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Thermarest sleep liner grey: £45.95, Gaynors​

Thermarest fixes one of the greatest flaws of sleeping bag liners by incorporating a three-quarter-length zip into its design: no more awkward shimmying in and out of the liner. It’s soft to the touch and made of easy-to-wash (and quick to dry) brushed polyester. It adds about 3 degrees of warmth to a sleeping bag, but really comes into its own when paired with Thermarest’s blankets and quilts, which it can fasten to using sewn-in loops to build up a flexible sleep system that’s ideal for huts, bothies or hostels. Mummy shape only.

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Quechua cotton liner: £12.99, Decathlon

If all you want is to add an extra few degrees to your bag, or spend a couple of nights in hostels, why overcomplicate things? Quechua’s rectangular cotton liner is a perfect entry-level liner if you’re not sure they’re for you. The rectangular shape gives your feet a bit more space to move around – this is noticeable even inside a tapered mummy bag as well as a rectangular bag. Being made of cotton means the liner is breathable and comfortable: you could happily sleep inside this in warmer, tropical temperatures – perfect for a hammock in southeast Asia – and save hundreds on a lightweight sleeping bag. Be warned, it doesn’t pack up small and it’s not particularly light.

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Snugpak TS1 insulating liner: £39.85, Snugpak​

If it’s good enough for the military, it’s good for your micro-adventure in the Lake District or your hostelling trip across Europe. Snugpak, a supplier for the army, is unfailingly dependable: its TS1 has a lovely, luxurious suede finish that feels really warm but is also breathable, wicks away moisture and is easy to wash. Best of all, though, are the tie-in loops: paired with a Snugpak bag, they ensure your liner won’t slip down inside your bag if you move around in the night.

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Trekmates microfleece liner: £20, The Climbers Shop

A real veteran’s brand, Trekmates has been the backpacker’s brand of choice for decades. Its products are sturdy and cheap and this liner, one of the brand’s more expensive, hovers around the £20 mark depending where you shop, but because it’s made of soft warm fleece it does beautifully on its own in an over-air-conditioned hostel. The warmth it adds to your sleeping bag might be psychological – you can’t expect too much at this price – and do avoid getting it wet, because cold, damp fleece is horrendous. That aside, there is something undeniably comforting about wrapping yourself up in a giant, warm fleece for the night.

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The verdict: Sleeping bag liners

For our reviewers the Cocoon merino liner was a game-changer. Even our testers who weren’t converted to the idea of a sleeping bag liner agreed they would opt for this soft, woollen liner over a sleeping bag in some conditions. For warmer weather, Rab’s silk liner is a light and lovely option. Thermarest’s zip-opening liner – good for cooler weather – is a really welcome innovation.

IndyBest product reviews are unbiased, independent advice you can trust. On some occasions, we earn revenue if you click the links and buy the products, but we never allow this to bias our coverage. The reviews are compiled through a mix of expert opinion and real-world testing.