Summer is over, but that doesn’t mean your camping trips must end, too. Especially with the right kit, you can still enjoy crisp winter nights in relative comfort. We’re looking at the best cold weather sleeping bags to help you extend the camping season. A winter sleeping bag alone may not be enough – it needs to be paired with a high R-rated sleeping mat and a decent tent – but it does go a long way! It is important to know your own limits, especially if you’re a cold sleeper!
Main image: The Mythic offered PTC ‘instant warmth’ | Credit: Daniel Hug
Choosing a cold weather sleeping bag is a game of compromise between weight, price, and warmth so you need to figure out which is more important to you. The fill type also impacts all of these. Down fill is warm and light but can be expensive, while synthetic is heavier, not as warm but usually cheaper.
Across Britain, winter temperatures can vary hugely. A night out could range from -15 to +5 degrees Celsius. Having a cold weather sleeping bag that is warm enough for the coldest nights, while still having options to vent a bit for warmer nights is useful, but that is a big range, so base your choice on where and when you plan to use the bag.
It’s generally a good idea to look for basic features like main zip baffles (aka draft tubes) which help to prevent cold spots, and anti-snagging zips, which reduce the chances of wrestling with your zip after a comfort break at 3am! A descent outer shell and a water resistant footbox go a long way in helping to retain warmth and improve durability, too.
Additional features that can be nice to have are pillow pockets, blanket collars, or zips to allow more ventilation, which can all help increase the comfort and the chance of a better night’s sleep.
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The best cold weather sleeping bags we’ve tested
| Quick List |
|---|
| Best for high camps: Rab Mythic 600 (available from Rab) |
| Lightest in test: Sea to Summit Women’s Ascent -9C (available from Sea to Summit) |
| Warmth-for-weight: Rab Neutrino 700 Pro (available from Cotswold Outdoor) |
| Best for bigger bodies: Therm-a-Rest Questar (available from Cascade Designs) |
| Best value: Mammut Women’s Perform Down Bag -10C (available from Mammut) |
Lightest in test
Sea to Summit Women’s Ascent -9C
Fiona Russell’s Best in Test
The Sea to Summit Ascent is not a cheap but it has good versatility and would serve as both a three and four-season bag.- warmth
- women’s shape
- fit
- versatility
- weight
- cost
| Quick specs |
|---|
| Price: $429 / £450 (available from Sea to Summit) |
| Weight: 797g |
| Fill: 750+ fill power RDS certified goose down with “Ultra-Dry Down” treatment |
| Shell: recycled 20-denier nylon shell and lining; 10-denier nylon waterproof-breathable hood and footbox |
| Construction: box wall baffle, plus vertical chest baffles and horizontal baffles lower half |
| Zip: 3 x 2-way zips full length, half length & toe box |
| Length: 170m (reg), 185cm (long) |
| Rating: -9C comfort, -15C lower limit |
| Sizes: regular and long |
| Women/Men’s version: yes |
| www.seatosummit.co.uk |
There is very little to fault in the Sea to Summit Ascent women’s sleeping bag. It is very well constructed and roomy enough to wriggle about inside and also curl up. The women’s bag, compared to the men’s bag, is wider at the hips and narrower at the shoulders to better suit the female physique. The bag is on the weightier end of those on test although you would expect a warm winter sleeping bag to a fairly heavy and bulky. It does pack down to a fairly neat size in the compression sack. The product comes with a zipped stuff bag, too.
Sea to Summit Ascent Women’s -9C is not a cheap at £450 for regular – and £475 for long – but it has good versatility and would serve well as both a three and four-season bag. A small annoyance is the zipped internal pocket that is hardly big enough to fit much more than a set of keys. Sea to Summit gives a nod to eco-goodness with RDS down and polyester in the main body fabric that is 100% Recycled Claim Standard (RCS) certified.
Read more: Fiona’s full Sea to Summit Ascent Women’s -9C review
Best for high camps
Rab Mythic 600
Peter Macfarlane’s Best in Test
The weight, pack size, comfort and performance all tie together to make the Rab Glacier 700 excellent for carrying into the winter hills for high camps as well as camp site and bothy use.- comfort
- weight
- performance
- price
| Quick specs |
|---|
| Price: $886 / £660 (available from Rab) |
| Weight: 886g |
| Fill: 600g of 900FP European Goose Down with Nikwax Fluorocarbon-Free Hydrophobic Finish |
| Shell: 10D Recycled Atmos 27gsm polyamide with Fluorocarbon-Free DWR, inner and outer |
| Construction: chevron pattern trapezoidal baffles, zip baffle, adjustable hood and shoulder baffle |
| Zip: ¾ two way |
| Length: 215cm |
| Rating: comfort: -5°C; limit: -12°C; extreme: -32°C |
| Sizes: one size |
| Women/Men’s version: unisex |
| rab.equipment |
The Rab Mythic 600 is by far the lightest bag I had in this comparative test but there are no corners cut to reach the weight. The fabric and components are very light and the quality of the down is very high. Loft is very good and the bag is extremely compressible for packing. I could have easily compressed it more than the 20cm x 23cm I measured in the sack I used for the review. The DWR finish is very good with wetting out taking a long time to occur and the down inside is hydrophobic to retain performance when it does get wet.
Other features are limited to hanging loops to keep with the minimalist light weight of the nature of the bag. The weight, pack size, comfort and performance all tie together to make the Rab Glacier 700 excellent for carrying into the winter hills for high camps as well as camp site and bothy use, but this performance does come at a price.
Read more: Peter’s full Rab Mythic 600 review
Best range of sizing
Thermarest Questar 0F/-18C
Steph Wetherell highly recommends
As a size 20 woman, finding sleeping bag for the winter months has been a mission. The Questar has solved this issue.- spacious
- very warm
- mat connectors
- none
| Quick Specs |
|---|
| Price: $409.95 / £360 (available from Cascade Designs) Weight: 1.17kg (small), 1.21kg (regular), 1.38kg (long) Fill: 650 hydrophobic down Shell: 20D Polyester with DWR Zip: eg 2-way full length YKK Auto lock centre Length: 185cm (small), 203cm (regular), 216cm (long) – to fit 168cm (small), 183cm (regular), 198cm (long) Rating: -10C comfort, -18C limit Sizes: Small, regular, long Women/Men’s version: Unisex cascadedesigns.com |
As a size 20 woman, finding sleeping bag for the winter months has been a mission. I’ve tried to squash myself into an assortment of bags over the years and never found one that I could turn over inside. It’s not just about comfort either – a tightly fitting bag also stops the down insulation performing properly, undermining the very feature you need in a warm bag. The Thermarest Questar has solved this issue though.
As a cold sleeper, the -10C comfort rating is enough for my winter outings, but the 1.2kg weight and fairly small pack size and well-designed compression sack means that I can still comfortably carry it on multi-day trips if needed. With any down sleeping bag there’s a concern about if the bag gets wet but the 650 Fill Duck Nikwax Hydrophobic Down is designed to absorb a lot less water and dry really quickly. It’s overall a warm bag, backed up by some nice features, including a foot pocket to help warm your feet up (which took me a bit of hunting with my feet to find the first time) and the insulation being zoned around key areas. Another nice feature is the thick baffle down the zip, and around your neck and the hood, which helps keep you toasty warm when you’re zipped and cinched in. In combination with a decent mat, it’s kept me warm even in sub-zero temperatures (something I’ve historically struggled with), and the down has stayed well distributed even with a good amount of use.
Read more: Steph’s full Therm-a-Rest Questar review
Warmth-to-weight ratio
Rab Neutrino Pro 700
Chris Townsend highly recommends
I found the bag very comfortable on the many nights I used it over the last winter and spring in temperatures ranging from 3°C to -9°C and all the features work really well.- warmth for weight
- recylced fabrics
- confusing temperature ratings
| Quick Specs |
|---|
| Price: $358.45 | £550 (available from Cotswold Outdoor) Weight: 1130g (Reg) Fill: 700g 800 fill power RDS certified goose down with Nikwax Fluorocarbon-Free, Hydrophobic Finish Shell: 20D Pertex Quantum Pro recycled nylon ripstop with microporous water-resistant coating and non-PFC-DWR outer, 20D recycled nylon inner Construction: trapezoidal boxwall with differential cut Zip: YKK ¾ length with synthetic filled baffle Length: 215cm (Regular), 230cm (Long) Rating: Comfort -4°C, Limit -10°C. Rab sleep limit -15°C Sizes: two Women’s version? No direct equivalent rab.equipment |
The Rab Neutrino Pro 700 is a lightweight sleeping bag suitable for UK winter use that provides excellent warmth for the weight. It’s a tapered mummy in shape, roomy around the shoulders, narrowing significantly round the legs, and then expanding again at the foot. The baffles are chevron shaped which reduces the amount of fabric compared to standard horizontal baffles. Internally the trapezoid box wall construction and differential cut are designed to allow the down to loft fully. The down is 800 fill power and has a Nikwax hydrophobic treatment to resist moisture. This is aided by the Pertex Quantum Pro outer which has a thin water-resistant coating and a PFC-free DWR.
Rab gives the bag a ‘Sleep Limit’ of -15°C, a figure written prominently on the side of the bag and also on the zip baffle. In use I found the bag warm at -9°C wearing just boxer shorts and a thin base layer top. I am a warm sleeper and I found the bag very comfortable on the many nights I used it over the last winter and spring in temperatures ranging from 3°C to -9°C. The features work well. The zip doesn’t snag, the hood and neck baffle are easily adjusted, and the narrow fit didn’t prove restrictive (though it might if you’re heavily built). A roomy waterproof drybag is provided. It weighs 70g. By compressing the bag inside I can get the packed size down to 33 x 24cm, which is compact for a winter bag.
Read more: Chris’ full Rab Neutrino 700 Pro review
Best for customisation
PHD Greenlandic 500
Fione Russell recommends
PHD bags are amazingly warm for weight and highly customisable – but at a price.- warmth
- weight
- customisability
- cost
| Quick specs |
|---|
| Price: From £792 |
| Weight: 965g (start from 890g) |
| Fill: 950 fill power European Goose Down |
| Shell: “Ultrashell” rip-stop nylon, 7X rip-stop nylon lining |
| Construction: straight wall baffle |
| Zip: 1-way half-zip |
| Length: standard |
| Rating: -10C comfort |
| Sizes: Standard, short, long, extra long (also slim-fit, wide and extra wide) |
| Women/Men’s version: unisex, customised fit |
| www.phdesigns.co.uk |
The PHD Greenlandic 500 is not as wide as other bags in this review, but it was enough for me to have a bit of wriggle room. Pulling my knees to my chest was also possible but the bag then felt a bit constraining. Weight-to-warmth ratio is very hard to beat and PHD use a 950-fill goose down that they adjust to give the same warmth rating whatever width and length of bag you choose. The Greenlandic 500 is delightfully warm yet the bag is also incredibly light in comparison to others.
There are not many finer features. For example, there is no shoulder baffle and the zip is a simple one-way with no zip garage. The zip fastener at the top of the bag is a basic fabric tab and velcro. PHD do not send the sleeping bags with compression sacks, so you need to buy your own if you want to eliminate more of the air. I have knocked off half a point on the score because of the cost.
Read more: Fiona’s full PHD Greenlandic 500 semi-rectangular down sleeping bag review
Mountain Equipment Glacier 700
Peter Macfarlane recommends
The Glacier 700 is an warm and lightweight bag for high winter camps but it does limit movement with a close cut- comfort
- performance
- slightly narrower fit
| Quick specs |
|---|
| Price: £400 |
| Weight: 1180g regular |
| Fill: 699g of minimum 700 fill power Down Codex-approved duck down |
| Shell: DRILITE® LOFT™ polyamide outer with FC free DWR, recycled polyamide inner |
| Construction: trapezoidal and slated box wall baffles, zip baffle, adjustable hood and shoulder baffle, lode lock magnetic closure |
| Zip: ¾ length two way |
| Length: 205cm regular |
| Rating: comfort: -6°C limit: -13°C extreme: -34°C |
| Sizes: regular and long |
| Women/Men’s version: yes |
| www.mountain-equipment.co.uk |
The Mountain Equipment Glacier 700 is a very clean looking bag, a classic mummy outline with horizontal baffles and no extraneous features at all. Even the hang loop for drying and airing at the foot is as minimalist as can be with just a single small shell fabric tunnel to thread your own loop through.
The performance is high and it’s the second warmest rating in the bags I tested. When inside the feedback and warmth is instant. The Mountain Equipment Glacier 700 is an excellent bag to climb into at camp but it is a cut quite close and I find movement not quite as easy or as natural inside as I did on the other bags in the review, especially on legs as I often sleep with one leg bent up a little. The down fill lofts is extremely well and is protected by a DWR finish on the outer fabric that just doesn’t want to wet out. The weight is good and the compressed pack size of 20cm x 25cm is a good fit in a winter pack for carrying the Glacier 700 high up the winter hills.
Read more: Peter’s full Mountain Equipment Glacier 700 review
Best value overall
Mammut Women’s Perform Down Bag -10C
Lucy Wallace recommends
A quality down bag is always a significant investment, but this one strikes a clever balance of performance, comfort, and affordability that will suit a broad range of users.- weight
- price
- down fill
- a good compromise of warmth
- Not as warm or light as some pricier options
| Quick Specs |
|---|
| Price: $299 | £370 (available from Mammut) Weight: 1166g with stuff sack Fill: 542g 700 fill power 100% RDS recycled grey duck down Shell: 100% Polyamide Construction: Box Wall Zip: 145cm two-way YKK Length: max height 180cm Rating: Comfort-3 /Limit-10 Sizes: M Men’s version? Unisex version available rated to -7 limit www.mammut.com |
Mammut’s women’s sleeping bags complement their men’s/unisex range with features specifically tailored to the average female physiology. This isn’t a gimmick: women typically sleep cooler and are more prone to cold spots around the thighs and glutes due to body fat distribution. To address this, the Mammut Women’s Perform Down Bag -10C is rated 3°C warmer than the standard model. It’s also slightly shorter, but with a maximum recommended height of 180cm, it’s longer than many women’s-specific bags. For me, this was a big win as I’m often too tall for women’s bags. This time I could stretch out and still feel snug. Comfort is excellent. The mummy hood has a soft, rustle-proof lining, and the neck baffle seals in warmth beautifully. I was sceptical about the central zip at first, but it was actually quite handy, especially when sitting up.
In terms of performance, I was impressed. As a mid-spec bag, it’s warm enough to be comfortable year-round on most UK mountains and in a wide range of conditions. It isn’t quite warm enough for a snowy camp on the Cairngorm Plateau though. While there are lighter, warmer bags available with higher fill-power down, they’re often much pricier and strip out features I really valued here such as the hood lining, and generous build. A quality down bag is always a significant investment, but this one strikes a clever balance of performance, comfort, and affordability that will suit a broad range of users.
Read more: Lucy’s full Mammut Perform Down Bag review
Mammut Women’s Relax Down Bag -2C
Fiona Russell’s recommends
The Mammut Women’s Relax Down Bag -2C is a great product for colder conditions when weight really matters.- weight
- fit
- price
- warmth
| Quick specs |
|---|
| Price: £320 |
| Weight: 900g |
| Fill: 280g 700 fill power, responsible down, 90% grey duck down, 10% grey duck feather |
| Shell: 52% Polyester, 48% Polyamide; lining: 100% Polyester & 55% Polyamide, 45% Polyester |
| Construction: box wall |
| Zip: 2-way full-length |
| Length: medium |
| Rating: -2C comfort limit |
| Sizes: medium |
| Women/Men’s version: yes |
| www.mammut.com |
This lighter weight bag just meets the criteria for our winter sleeping bags, so if you are a cold sleeper or it’s going to be consistently below -2C, I recommend you choose another bag or wear a down jacket and thick socks. However, it is a great product for colder conditions when weight really matters. The length is great and made to fit women of between 165cm to 180cm height. The width gives room for some movement inside the bag.
The soft feel fabric on the inside of the large hood is a brilliant extra feature because it means your ears are not filled with the sound of sleeping bag when you move about at night. You could muffle even more noise – and the sounds of snoring fellow sleepers – with the handily provided ear plugs. There is also an eye mask tucked into a mesh pocket in the compression bag.
Read more: Fiona’s full Mammut Women’s Relax Down Bag -2C review
Gruezi-Bag Biopod Down Hybrid Ice Cold
Peter Macfarlane recommends
The features and elaborate design add up to extra bulk which makes this a better winter base camp bag than one I’d carry onto the hill.- comfort
- performance
- heat pad
- weight
- pack size
| Quick specs |
|---|
| Price: £540 |
| Weight: 1545g |
| Fill: 700g 90/10, 800+ RDS certified goose down, lavalan AlmWolle wool upper layer |
| Shell: Recycled, breathable and water-repellent ultra-light 20 denier 380T nylon outer, recycled nylon inner |
| Construction: V shaped chambers, box chambers, wool overlay, zip baffle, external zipped pocket, adjustable hood and shoulder baffle, powerbank compatible heat pad in foot box |
| Zip: 2-way full length zip |
| Length: 215cm |
| Rating: comfort: -5°C limit: -12°C extreme: -31°C |
| Sizes: one size |
| Women/Men’s version: unisex |
| www.gz-bag.de |
The Gruezi-Bag Biopod is an extremely comfortable bag with a cut that’s a little relaxed. I can lie inside in various natural positions with my elbows out and my knees bent leg bent. The hood is large and warm and can be cinched right in if need be and the hood and baffle adjusters are easy to operate whilst inside. The main zip is a standard type but the main zip puller has a wide plastic attachment which seems to greatly reduce snagging when using the zip.
Another unusual feature the bag has is a pocket at the left chest where you slip in a power bank that connects to a thin wire that runs down to the foot box where it powers a small heat pad. This adds relatively little weight or bulk and is excellent if need a boost of heat. There is also an external zip pocket which is handy for a head torch. The underside has anti slip pads and loops for securing to a matt. The outer fabric DWR is decent for splashes but the fabric does wet out over time against a damp tent inner. The features and elaborate design add up to extra bulk and weight with a compressed pack size of 33cm x 23cm which, for me, makes this a better winter base camp bag than one I’d carry onto the hills.
Read more: Peter’s full Gruezi-Bag Biopod Down Hybrid Ice Cold review
Robens Serac 900 -20°C
Peter Macfarlane recommends
The performance is high and it’s almost hidden under a price which is very good indeed.- comfort
- performance
- price
- weight
- pack size
| Quick specs |
|---|
| Price: £351.99 |
| Weight: 1490g |
| Fill: 900g of 600 FP 85/15 RDS certified duck down |
| Shell: recycled 20D 400T nylon ripstop outer, recycled 20D 400T nylon taffeta inner |
| Construction: stretch box baffles on upper body, box baffles, zip baffle, adjustable hood and shoulder baffle |
| Zip: ¾ length two way |
| Length: 220cm |
| Rating: comfort: -12°C limit: -20°C extreme: -43°C |
| Sizes: one size |
| Women/Men’s version: unisex |
| www.robens.de |
The Robens Serac 900 looks like it has quite a trim fit, but once inside the stretch seams on the upper body baffles allow very good arm movement whilst keeping the down close to your body for very good feedback (the feeling of warmth from the insulation) from the down fill insulation. This is very comfortable and feels very natural to sleep in as I can move around pretty normally.
The comfort extends to the well-shaped hood and the shoulder baffle which fit and function well. These are easily adjusted from inside the bag via a toggle which has different shaped cords running through it to adjust the upper and lower hood and a bungee inside for the baffle. The weight is getting quite high at a kilo and a half and the packsize compressed is a chunky 26cm x 23cm but the performance is high and it’s almost hidden under a price which is very good indeed.
Read more: Peter’s full Robens Serac 900 -20°C review
How we test
Fiona is 173cm tall and UK10. She is a cold sleeper. She is also a side sleeper and likes to be able to move her legs around and curl up inside a sleeping bag. These bags were tested in winter temperates below 0C throughout 2023/2024.
Peter used the bags at camp and in bothies from late autumn 2023 to spring 2024 over a variety of conditions and temperatures. The packed sizes were taken from putting each the same compression sack and the weights were taken on digital scales without any stuff sack.
Steph used this sleeping bag through the winter and spring months between 2024 and 2025 in South Wales and the South West of England. She is an especially cold sleeper, and plus size (size 20) so requires a warm and spacious sleeping bag.
Features to look for in winter sleeping bags
Shape and size
Cold weather sleeping bags often come in a regular and long size, so choose appropriately for your height. A mummy shaped bag hugs your body, making the best use of the insulation. Spoon shaped bags are best for side-sleepers. Women’s bags are generally designed to be shorter and may have insulation in different places to men.
Weight
There is usually a compromise between weight, insulation and price. An ultralight bag will be easier to carry, but either less warm or more expensive, or both.
Fill
Down insulation is very warm, lightweight and compressible, but far less effective when wet. Look for hydrophobic down – this has been treated to improve its water resistance. The higher the down fillpower (FP) rating, the higher quality and warmer the down for its weight. Synthetic insulation is heavier and less durable, but cheaper, quicker to dry and still retains some insulation value when damp.
Shell
A shell material with a higher Denier rating will be more durable, but also heavier. The lightest materials may allow feathers to escape through the material more easily on down bags. For water resistance, look for bags with a water-resistant (DWR) treatment.
Baffles/draft tubes
A draft tube of insulation-filled material running the length of the main zip (inside) helps to prevent heat loss. A draft collar around your shoulders is also crucial in a winter sleeping bag.
Zips and ventilation
These are usually 3/4 length. Shorter zips save weight. Two-way zips allow ventilation. Some bags offer features such as footbox vents.
Temperature ratings
Standard ISO ratings allow you to compare temperature ratings. ‘Comfort rating’ is the temperature at which a ‘standard woman’ is ‘not feeling cold’. ‘Limit rating’ is the temperature at which a ‘standard man’, curled up, resists hypothermia. Comfort in different temperatures varies widely between individuals and will depend on the effectiveness of your overall sleeping system.
Ethics
Down bags contain duck/goose products. Look for RDS certification for cruelty-free down. Synthetic bags can be made from recycled products but have a shorter lifespan, and microfibres can cause environmental issues.
