Best lightweight sleeping bag 2020, to keep you cosy without weighing you down

Hunting for the best lightweight sleeping bag? Read on. Any outdoor overnighter will involve a sleeping bag, and if you're carrying it – say on a hiking trip or similar – then you'll be aware that even a high-quality bag can weigh in quite heavy. Indeed, the sleeping bag is one of the best areas to save weight… but not by going cheap, unfortunately. 

Really super-lightweight sleeping bags are – more than any other outdoor kit – very specialised. They'll do one thing brilliantly, but that's the price you pay for lightness. However, there are many excellent lightweight bags that will shave many grams while still being useful for more than one trip. Or in other words, a sound investment in comfort. 

Perhaps unnecessary to point out, but getting obsessed with weight alone is a road to a very light bag but a very uncomfortable night. You'll almost definitely want to balance your needs with some caution, and also bear in mind that those stupidly light quilts are only comfort rated down to 8 degrees, which is the equivalent of sleeping just in a jumper. It's those tradeoffs that need to be cynically weighed up – the quarter zip saves a few grams, but means that hot nights are hell. Choose wisely with the aid of our specialised best lightweight sleeping bag guide below...

Make sure you pair your purchase with one of the best camping mats for a great night's sleep out in the wilderness. If weight isn't an issue – for example if you're car camping – check out our general list of the best sleeping bags right now.

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Best lightweight sleeping bag: our expert pick

• It's obvious, but we'll say it anyway: the big difference between 'normal' sleeping bags and lightweight sleepers is the fact that they are much lighter overall. These bags will keep your pack weight down, which is essential if you’re backpacking or on a multi-day hiking trip and need to move fast and light. But sometimes they do compromise on warmth and comfort.
• The Rab Mythic Ultra 180 is not only hysteria-inducingly light, but also properly featured enough to use as a normal sleeping bag. The key metric here is the warmth rating, which at a limit of zero degrees is pushing three season UK use, an astonishing feat for such a light bag. Packed with quality goose down and aided with titanium bonding trickery to boost heat, this is a fantastic lightweight bag for any occasion. 

How to choose the best lightweight sleeping bag

There are a few things to know before you make your purchase. Sleeping bags usually state an EN rating, which is the European standard EN13537. EN13537 uses a thermal manikin test that produces four temperature results: upper limit, comfort, lower limit/transition, and extreme. Of these four ratings, ’comfort’ and ’lower limit/transition’ are the most helpful and are what most people look at when buying a sleeping bag.

If you get colder faster than the average person, look at sleeping bags with a higher lower limit. Remember too that real-world variables can have an impact on the performance of a sleeping bag, so these ranges are just a guideline.

Even in the summer heat temperatures can drop at night, and even more so as you climb above sea level (approximately 1 degree less for every 100m), so single-figure EN ratings are a good choice even for a light UK summer sleeping bag.

Unfortunately, while technological advancements mean that most hardware is getting lighter and lighter, there are still limits to what you can do, and nowhere more acute than in sleeping bags. Lighter materials shave off those grams, but lose lots of durability. Elsewhere, DWR coatings and treatments might add vital damp-proofing, but also add in a few grams themselves – there's literally no escape from the scales.  

Down filling offers the lightest and warmest potential, but is pretty useless in damp conditions, while artificial fibres tend to be heavier and bulkier, but much happier in soggy UK conditions. 

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The best lightweight sleeping bags to buy now

The best lightweight sleeping bag right now is the Rab Mythic Ultra 180. Rab's new flagship earns yet another leading slot here, not only because Rab has a lot of good history building excellent sleeping bags, but because this one is highly technical, and really, really light. There are various weights in the range, so you can pick the best version for your lifestyle, but the lightest, the 180, clocks in at 400g. Yeah, 400 – less than four Mars bars. It's still limit rated to zero degrees too, which means it'll handle a wide range of outdoor excitement and still keep you happy. 

Part of this achievement is down to top-notch materials, part to technical innovation. Rab has knocked up a world first –  Thermo Ionic Lining Technology (TILT). This impressive-sounding acronym is actually a coating of Titanium bonded to the fibres, enabling them to reflect heat back at you, boosting warmth. It's a canny trick, and most importantly doesn't add much in the weight department. 

New in 2019, the Thermarest Hyperion 32UL boasts an enormous 900 fill GooseNikwax Hydrophobic Down to keep you warm down to a comfort limit of zero degrees, which is impressive considering how light this is. It also packs down to around the size of a 1L water bottle. The Nikwax treatment on the down itself staves off some of the worst effects of damp, with the treatment staying drier and, according to Nikwax, maintaining loft 60 times longer than untreated down. 

A thermally-efficient box baffled construction and zoned fill (70% on the top and sides with 30% on the back) keeps the insulation around your core for maximum warmth and minimum weight, and finally the down filling is Responsible Down Standard Certified. It's not cheap, but it is the best lightweight sleeping bag you can buy, and after a long day carrying it, you won’t regret spending the pounds (or dollars) to save those grams.

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If you're on a tight budget, check out the Decathlon Forclaz Trek 900. The folk at Decathlon have been busy here, knocking out a sub-700g mummy sleeping bag for a fraction of the price of the top performers in this class. There's a full length zip too, making this a very flexible late spring/summer/autumn bag indeed. 

However, the temperature rating is where this falls down, considerably less warm than some of the competition. The key reason for that is the fill material, mixing in much cheaper duck feather to bring costs down, as well as a standard polyester outer. The upside of that is that this bag is washable, and ‘water repellent' according to Decathlon, although we'd take that with a pinch of salt. Overall: good design, good lightness, good price, budget materials – well worth a balanced  look.

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As with the Rab Mythic, the Sea to Summit Spark range includes a range of bags for all occasions, but we're going for the lightest available in the UK, the Sea to Summit Spark spI. That clocks in at a powerfully light 340g, quite astonishingly, in part due to the premium goose down, and a cunning design that boosts loft over the chest area with vertical baffles. That down has been dry treated too, widening the range of outdoor applications into adventure racing and the like. Even more impressively there's a half-length zip, something of a luxury when going this light. 

The downside of all that lightness is a 9°c comfort rating, which is fairly warm for the UK, and really limits what you can get up to with this bag. However, that is the tradeoff, and for just a few grams (490 of them) you could get the Spark sp2 that'll cope with 4°c – the choice is yours...

Whether you take into account the budget price tag or you don’t, the Vango Ultralite Pro 100 is an impressive sleeping bag. The Thermal Reverb system of reflective aluminised lining bounces body heat back to you, and the Polair Active outer fabric remains soft and warm to the touch. At 900g it’s not feather-lite, but it’s still compact and comfortable to carry when backpacking and hiking. Better still, it comes recommended by both the DofE and The Scout Association. 

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The Mountain Hardwear Lamina line is packed with light-for-their-warmth synthetic bags, and this is the lightest in the family. Coming in just under a kilo, it’s heavier than some but also very robust. A 30D Nylon Ripstop shell will last years, and the Thermal.Q artificial down insulation will keep you toasty in all weathers down to minus one degrees - an ideal combination for UK adventures. 

Although the comfort rating stops at a chilly three degrees, Mountain Hardwear have set a ‘comfort limit’ at minus three, which is really plumbing the mercury for such a light bag. This is partly achieved through thermal mapping, which allocates the heaviest insulation to where it is most needed, around your core. In addition, the ingenious design of the Lamina line all adds up to a bag that punches well above its weight, such as the draft collar, tailored hood and anti-snag zip. 

The Mountain Equipment Helium 250 is a lovely bag for summer adventures, and the build quality will last for ages too. Weighing in well under a kilo it’s no heavyweight, but the 254g of 90-10 Pure Duck Down fill will take some looking after to deliver the full insulation rating of a comfort rating of 8°C, with a limit at 3°C (extreme is a scary -11°C, which is very unlikely in summer).

As you’d expect from Mountain Equipment, the Helium spec list reads well, even though it’s not the lightest down bag here. An Alpine cut keeps heat trapped, and Slanted Box-Wall baffles should keep the down well distributed and lofted. Elsewhere there's an anatomically shaped hood and anatomically shaped foot-box, plus a heat-retaining internal collar. The included waterproof roll-top stuff-sack will help protect your down bag if exposed to the elements.

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A beautifully warm synthetic lightweight sleeping bag for summer camping and adventure trips. The Oscar has been created from ultra-fine 7-denier ripstop nylon and 100% recycled synthetic filling made from PET bottles. It packs down very small, making it ideal for backpacking and bike-touring trips in warmer weather, and has a half-length zipper for better ventilation. If you're a wriggler, you'll enjoy the trapezoid footbox, which offers more room. The Nordisk Oscar +10 has an integrated pack sack (designed with compression straps) and comes with an extra mesh storage bag for neater packing.