8 Best Ultralight Sleeping Bags for 2024

We tested the best ultralight sleeping bags for 2024 and this is how they performed.

Updated on January 8th, 2024
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As one of the biggest items in your pack, your sleeping bag needs to be compressible and lightweight while providing sufficient warmth and comfort for a good night's sleep outdoors. 

We tested the best ultralight sleeping bags on the market for 2024. Read on to see what we found, which is best for you, and get some buying advice.

Disclaimer: This is a post about sleeping bags, specifically. For the best quilts, check out this article. For two-person sleeping bags, check out this article.

Best Backpacking Sleeping Bags

The best backpacking sleeping bags are:

The product comparison table below is sortable. Click the arrow in the heading cell to sort the models by preferred spec.

MODEL Weight Warmth Fill PRICE L x W Denier Volume
1. Zpacks 20F Classic Sleeping Bag 1lb 2.8oz 20F 900 $449 72 x 50in 7D 6L 9/10
2. REI Co-Op Magma 15 1lb 12.2oz 16F 850 $399 72 x 63in 15D 5.2L 9/10
3. Therm-a-Rest Hyperion 1lb 4oz 20F 900 $500 80 x 28.5in 10D 3L 9/10
4. Mountain Hardwear Phantom 15 2lbs 15F 850 $550 86 x 56in 10D 5.7L 9/10
5. Marmot Phase 20 1lb 6.5oz 20F 850 $480 72 x 60in 10D 5.3L 9/10
6. Sea to Summit Spark Ultralight 1lb 7.5oz 18F 850+ $489 72 x 59in 10D 4.6L 9/10
7. Montbell Seamless Down Hugger WR 900 1lb 14.5oz 15F 900 $650 72 x 53in 13D 5.1L 8/10
8. Western Mountaineering Ultralite 1lb 13oz 20F 850+ $580 72 x 59in 12D 8.7L 8/10

Best Overall Ultralight Sleeping Bag for Weight, Warmth, and Affordability:


Price: $419

ZPACKS 20F Classic Sleeping Bag

✅ Ultralight

✅ Great warmth-to-weight ratio

✅ High fill power

✅ Affordable


❌ Tight fit

❌ Not as durable

❌ No hood


  • Weight: 1 lb 2.8 oz
  • Warmth: 20F
  • Fill: 900 Goose Down
  • Dimensions: 72 x 50 in
  • Shell Denier: 7D RipStop Nylon
  • Volume (Compressed): 6L

The Zpacks 20F Classic Sleeping Bag is an ultralight backpacker’s dream. Weighing in at just over a pound it’s the lightest bag we reviewed. It’s also versatile and can be used as a sleeping bag or a quilt thanks to the ¾ length zipper. Our favorite feature of this bag is the incredible warmth-to-weight ratio it provides. We were seriously impressed that a bag this light can keep you toasty down to 20F. We love the 900-fill goose down, the highest fill power on our list (tied with the Montbell Down Hugger).

To get the bag down to this weight ZPacks did have to cut a few corners, like discarding the hood. We also found this bag to be less spacious than other models. With the 7D nylon shell thickness, we would recommend treating this bag with care as it’s less durable than other ultralight models we tested. The ZPacks 20F Classic Sleeping bag is our pick for the best ultralight sleeping bag. Read in-depth review of the Zpacks 20F Classic Sleeping Bag here.

Most Affordable Ultralight Sleeping Bag:



✅ Warm bag

✅ Most Affordable

✅ Spacious

✅ Durable


❌ Not the lightest on the list


  • Weight: 1 lb 12 oz
  • Warmth: 16F
  • Fill: 850 Fill Power Goose Down
  • Dimensions: 72 x 63 in
  • Shell Denier: 15D RipStop Nylon
  • Volume (Compressed): 5.2 L

The REI Magma 15 is a very warm sleeping bag made with 850-fill-power goose down and rated down to 16F.  This sleeping bag is more spacious than average and the 15D shell fabric is a bit more durable too. 

Even though it’s a little heavier than the lightest models on our list, The REI Magma 15 is highly affordable while being packed with value. The shell and the down are both treated with a DWR to assist with water resistance. And we love that you can fit a low-profile pillow in the hood. Read in-depth REI Magma 15 review.

Most Compressible Ultralight Sleeping Bag:



✅ Ultralight

✅ High warmth-to-weight

✅ High fill power

✅ High Compressibility


❌ Less spacious


  • Weight: 1 lb 4 oz
  • Warmth: 20F
  • Fill: 900 Nikwax Hydrophobic Down
  • Dimensions: 80 x 28.5 in
  • Shell Denier: 10D Nylon RipStop w/ DWR
  • Volume (Compressed): 3 L

The Therma-a-Rest Hyperion is only 1.2 ounces shy of being the lightest bag on our list. It also has the best warmth-to-weight ratio (tied with the ZPacks Classic sleeping bag) thanks to its use of 900 fill power Nikwax Hydrophobic Down.

This down is also treated with DWR allowing it to hold its loft better than other models we tested in damp conditions. We loved that it is a compact sleeping bag too. It packs down to just 3 liters in size. We did find it to have a more snug fit than other models. Overall, we found the Therma-a-Rest Hyperion to be an impressive bag. Read in-depth review of the Therm-a-Rest Hyperion here.

Most Spacious Sleeping Bag:

Mountain Hardwear Phantom 15


✅ Warm

✅ Spacious


❌ Expensive

❌ Heaviest on our list


  • Weight: 2 lbs
  • Warmth: 15F
  • Fill: 850 Fill Down RDS
  • Dimensions: 86 x 56 in
  • Shell Denier: 10D Recycled Shell
  • Volume (Compressed): 5.7 L

This is the most spacious bag on our list and with a 15F rating is one of the warmest on our list (tied with the Montbell Down Hugger). We like that the unisex Mountain Hardwear Phantom eliminates cold spots caused by traditional stitching and puts the warmth where you need it most, around your core and your feet. It has a mummy cut but is still very spacious thanks to its longer-than-average length.

Our biggest gripe with this sleeping bag is the price. At $550 it’s one of the more expensive models we tested. For a cheaper (but heavier) alternative, check out Mountain Hardwear's Bishop Pass 15 mummy bag.

Warmest Ultralight Sleeping Bag:


Price: $479

MONTBELL Seamless Down Hugger WR 900

✅ Incredibly warm

✅ High fill power

✅ Durable


❌ Expensive

❌ Less spacious

❌ Not the lightest


  • Weight: 1 lb 14.5 oz
  • Warmth: 15F
  • Fill: 900 EX Down
  • Dimensions: 72 x 53 in
  • Shell Denier: 13D Nylon RipStop
  • Volume (Compressed): 5.1 L

The Montbell Seamless Down Hugger WR 900 is a high-quality bag and also the warmest on our list (tied with Mountian Hardwear's  Phantom 15). It’s well-designed and we love that it’s made of high-quality materials including 900 fill down, which gives it high insulation power. We found the Down Hugger WR 900 does a great job at repelling water and moisture thanks to its seamless GORE-TEX Infinium Windstopper fabric. Instead of baffles, Montbell uses their proprietary Spider Baffle System to hold the down in place and preserve the loft of the bag.

This is a shorter and skinnier bag than most of the models we tested and at $650, this is the most expensive model we tested. However, we think this is an excellent pick for those wanting a warm premium-quality bag that weighs next to nothing.

For a cheaper option, check out the Down Hugger 800 (available in half-length).

The Other Noteworthy Models

Sea to Summit Spark Ultralight

SEA TO SUMMIT Spark Ultralight

✅ Packs down small

✅ Good warmth-to-weight ratio


❌ No outstandingly great specs (but good performance all around)


  • Weight: 1 lb 7.5 oz
  • Warmth: 18F
  • Fill: 850+ Loft Ultra-Dry Down
  • Dimensions: 72 x 59 in
  • Shell Denier: 10D Nylon
  • Volume (Compressed): 4.6 L

The Sea to Summit Spark Ultralight is another quality ultralight option, very similar to the Marmot Phase 20. One of the big differentiators to us is the shell of 10D UL nylon treated with DWR which provides a bit of extra weather protection. 

Sea to Summit kept the weight down by creating a simple mummy design without too many extra features. We do like the inclusion of a one-directional 1/3 length zip with a toggle at the head to allow you to totally cocoon yourself.

The low weight and 20F temperature rating give this a nice warmth-to-weight ratio too. We did find this to be a very compact sleeping bag (2nd for compressibility). We were able to compress this sleeping bag down smaller than most others on our list.

Marmot Phase 20

MARMOT Phase 20

✅ Comfortable

✅ Top 3 for weight

✅ Top 3 for affordability


❌ comparably low warmth-to-weight 


  • Weight: 1 lb 6.5 oz
  • Warmth: 20F
  • Fill: 850 Goose Down
  • Dimensions: 72 x 60 in
  • Shell Denier: 10D RipStop Nylon
  • Volume (Compressed): 5.3 L

At 1 pound 6.5 ounces the Marmot Phase 20 sleeping bag weighs only a few ounces more than the lightest sleeping bags on our list making it an excellent choice for ultralight backpackers. However, we found that the zipper occasionally snags.

It has a mummy cut, but we found it less constricting than other mummy bags we reviewed. The 850 goose-down fill feels like quality insulation to us and at $480 it is the 3rd cheapest model we tested. 

Western Mountaineering Ultralite


✅ Durability

✅ Good warmth and insulation


❌ Expensive

❌ Lowest warmth-to-weight on our list

❌ Heavier than other models


  • Weight: 1 lb 13 oz
  • Warmth: 20F
  • Fill: 850+ 16 oz Down
  • Dimensions: 72 x 59 in
  • Shell Denier: 12D
  • Volume (Compressed): 8.7 L

We love the Western Mountaineering Ultralight for its high lofting down and full draft collar, making this one of the coziest bags on our list. We found the 20F temperature rating to be fairly standard, but the warmth-to-weight ratio was the lowest on our list.

This is one of the heaviest bags we tested, but it is still well under 2 pounds. At almost $580 this is one of the most expensive sleeping bags we tested.

Key Factors To Consider When Choosing

Weight & Warmth-to-weight

The best ultralight sleeping bags feature a low total weight and an excellent weight-to-warmth ratio. How much should an ultralight sleeping bag weigh? A good weight for an ultralight sleeping bag is 2 pounds or less. Sleeping bags are one of the “Big 3” backpacking gear items (tent and backpack being the other two) and are one of your biggest opportunities to save weight.

Warmth-to-weight ratio is a measure of how much warmth for the weight a sleeping bag provides. Lower weight and higher temperature ratings have the best weight-to-warmth ratios.

The best ultralight sleeping bags:

 Ultralight sleeping bags with the highest warmth-to-weight:


The biggest price factors are fill material and fill power. The best ultralight sleeping bags use high-quality fill material and use high fill powers to insulate at featherlight weights and these come at a cost.

The highest value-for-money ultralight sleeping bags:

The most affordable ultralight sleeping bags:

The high-end ultralight sleeping bags:

Adequate Warmth

 When choosing a sleeping bag keep in mind how cold your nights will be, whether you are a hot or cold sleeper, what clothes you like to sleep in, and whether you will be in a tent or not. Sleeping bags are grouped by seasonal ratings: Summer (32° and higher), Winter (10° and lower), and 3-Season (10° to 32°). What is the warmest, lightest sleeping bag? The warmest, lightest sleeping bag we tested was the Zpacks 20F Classic Sleeping Bag.

Look for sleeping bags tested according to EN Standards and marked EN13537, which means the sleeping bag has undergone a "thermal manikin" test (a human model designed for scientific testing), not just independently tested by the manufacturer.

The tests are conducted on the basis that a person is using a sleeping pad, is in a tent, and wearing one layer of thermal underwear. A "standard" man is aged 25, 1.73 m in height, and weighs 73 kg, whilst a "standard" female is aged 25, 1.6 m tall, and weighs 60 kg. Keep in mind that a man normally sleeps "hotter" than a female and that everyone is a different shape and size, with different levels of "self" insulation.

There are 4 standard temperature ratings to keep you warm:

  • Upper Limit—when a male can sleep without sweating, with hood and zippers open and his arms outside of the bag.
  • Comfort—this is when a female can comfortably sleep in a relaxed position.
  • Lower Limit—the temperature a male can sleep uninterrupted for 8 hours in a curled position.
  • Extreme—this is the minimum temperature for a female for 6 hours without the risk of death from hypothermia - albeit a touch of frostbite is still a possibility.

The warmest ultralight sleeping bags:

Other Things to Consider


A sleeping bag’s insulation is what keeps you warm at night. Down and synthetic are the two types of insulation used in a sleeping bag. Down feathers are lighter, warmer, and pack down smaller than synthetics. The drawback to down is that if it gets wet, it loses its insulation. Synthetic insulation dries faster, keeps you insulated even when wet, and is budget-friendly. The drawback to synthetics is that they are heavy, and bulky, and each time you compress them, the insulating power is reduced.

packing away a sleeping bag

Fill: Down vs. Synthetic


down vs synthetic table

Down feathers are lighter, warmer, and pack smaller than synthetic insulation options. Down has an Achilles heel though - it loses loft and insulation ability when it gets wet. Losing insulation is a scary thought for winter backpacking. Down is more durable than synthetic fillings, but super expensive.

sleeping bag zippers
Double (two-way) zippers for flexible opening

Most down-filled sleeping bags have been treated with durable water repellent (DWR) in the factory process, which is fluoropolymer based and named "hydrophobic" down. This prevents the down filling from becoming a soggy mass with no ability to retain heat.

It is also known as "dry down". This treatment makes it water-resistant not waterproof, so don't expose your sleeping bag to a torrential thunderstorm or drop it into a stream. DWR will wear off over time and will require reapplying.

ff flicker ul

A synthetic insulated backpacking sleeping bag dries faster than down, it is non-allergenic and is less expensive to buy. On the minus side, the synthetic filling will give you less warmth for its weight, it is bulkier to carry and each time you compress it, the insulating power is reduced.

Technology has taken over from the old polyester fill for sleeping bags of the synthetic ilk and today there are 4 common primary fillers other than down.

sleeping bags overlooking mountains

Popular synthetic options on the market include:

  1. PolarGuard and 3D PolarGuard DeltaPolarGuard was the original version with 3D PolarGuard Delta the perfected product that will give the same insulation ability, but with reduced bulkiness and weight. Commonly used in high-quality three-season sleeping bags, it is easy to take care of; when wet, it will not lose its insulation properties and you can wash it in cold water in a washing machine.

  2. Quallofilon the heavy and bulky side, you won't see it in the lightweight or high-end-priced sleeping bags.

  3. Hollofil & Hollofil II—only used in bargain basement sleeping bags as it lacks insulating ability, is heavy, and is quite bulky.

  4. Thermolite—another cheap sleeping bag filling with no insulation to keep you warm.

I keep my sleeping bag well protected in a waterproof stuff sack, inside a waterproof pack-lined backpack, and I have never had a truly wet sleeping bag. If you can afford it and will keep it protected, I vote to go for down insulation along with protective storage.

hg burrow econ

Fill Power


‘Fill-power’ is a measurement of the density of down fill and accounts for the overall warmth-to-weight ratio. This typically ranges from 600 to 950. The higher the number, the more ‘quality’ the feather insulation is. It is calculated on how many cubic inches 1 ounce of down can fill a testing device. And, of course, the higher the fill of power down, the more expensive it is.

hikers cowboy camping in down sleeping bags
Pair your sleeping bag with a sleeping bag for warmth from both top and bottom.

Generally, an 850 fill power or higher is in the top quality bracket with a warmth-to-weight ratio. Keep in mind that a 700-fill-power down sleeping bag rated +20°F will be lighter than a 600-fill-power down bag rated +20°F. A 3-season sleeping bag normally has a rating of at least 600, but if you are planning on being in sub-zero weather you should be considering 900 to 1000-fill-power.

down fill for sleeping bags


After a long day of hiking, you don’t want to be confined into a tight cocoon. Many ultralight sleeping bags cut weight by making them narrow. This is a tough balancing act - space versus overall weight and bulk. A snug sleeping bag will be warmer, as it minimizes the air space around your body. Spacious sleeping bags give you freedom of movement, which is a dire necessity for restless souls, but they also require more precious body heat to fill.

kelty ultralight sleeping bag

There are 3 key measurements to take into consideration:

  • Length - opt for the shortest length that will fit your frame (to save weight), but ensure that your feet are comfy without being squished when you have the hood done up, as this will compress the insulation, which is what you don't want. Having a bit of extra room at the bottom of your backpacking sleeping bag gives you the option of having somewhere to stash some clothes and/or your hiking shoes. The regular male sleeping bags come in 2 standard lengths - up to 6ft and up to 6ft 6in. Female sleeping bags are usually up to 5ft 4ins and 5ft 10ins. When in doubt, get the extra length.
  • Shoulder girth - most of the male sleeping bags have a shoulder width of between 60 and 64 inches with narrow ones coming in at 58 inches. Female ones are slightly narrower ranging from 56 to 60 inches. An inch can make a huge difference on the snug level. The best way to determine the size you need is to test-drive a few different-sized sleeping bags.
  • Hip measurement - most men's sleeping bags will measure around 58 inches, whilst the women's tend to be a bit higher around 60 inches. Again, take a couple of sleeping bags for a test drive.

The most spacious backpacking sleeping bags:

klymit ksb 20 and rei tent


The outer shell of a sleeping bag is made out of either nylon or polyester. Fabric denier, how thick the material is, has the biggest impact on durability. The thicker the fabric, the more durable a sleeping bag will be.

The most durable backpacking sleeping bags:

klymit ksb 20 sleeping bag

Klymit KSB 20



This will vary a lot depending on your warmth and insulation needs. ie - a summer bag will compress smaller than a winter bag. By far, the number one thing that will account for the size of your bag (while packed) is the insulation fill. The fabric and design elements being the second and third. Down and synthetic fillings both have pros and cons (we'll get there in a sec), but down-filled sleeping bags pack down to the smallest sizes.

Compression straps and stuff sacks can significantly cut down on the volume your bag occupies in your pack. Ideally, you want it compressed as compact as possible while on the trail.

The ultralight sleeping bags that are the most compressible are:

blue sleeping bag



Should you buy 2 sleeping bags? One for the warmer months and one for the winter? If money is no issue, by all means, feel free to splurge. For the rest of us though, I think two is totally unnecessary. When in doubt, err on the warm side and get a full-on winter bag.

A winter bag can be compatible in summer but a summer bag just won’t cut it in winter. If the thick winter sleeping bag is too hot on summer nights, unzip it or just sleep on top of it in your bag liner.



A hood covers your head and cinches tightly, leaving only your face exposed. It traps your body heat inside the bag, helping to keep you warm. Hoods are cozy when you sleep on your back, but can get in your way when you turn to the side or sleep on your stomach. I'm a side sleeper and on more than one occasion, I've woken up in a panic with my head buried deep inside the hood.

backpacker sleeping in tent with sleeping bag

Most sleeping bags and quilts will be wider at the shoulders.

Pad Loops And Sleeves


Connecting your sleeping bag to your sleeping pad, the pad loops are sewn-in straps whereby you can secure your sleeping bag and prevent it from slipping off the pad. A pad sleeve is used as an insulated sleeping pad when the design of a lightweight sleeping bag has eliminated the bottom insulation to reduce overall pack weight, making it compress smaller than a conventional sleeping bag.

phantom sleeping bag

Mummy bag front (left) vs. backpacking quilt back (right)

Draft Collar


A draft collar is also known as face mufflers, a head gasket, or neck baffle and it is the insulated collar around the hood of a sleeping bag to guard against cold weather. It is referring to the insulated baffles in the sleeping bag that sit around your head and neck to prevent heat from escaping or the cold from leeching in.

The drawcords are differentiated, so that you can feel in the dark which one does what - loosens or tightens your hood.

klymit ksb 20


How much should an ultralight sleep system weigh?

An ultralight sleep system should weight 3 pounds or less.

Should I get two sleeping bags (one for summer and one for winter)?

You should get two sleeping bags if you plan on camping in extreme conditions on either end of the spectrum, like warm desert camping and frigid polar expeditions. If your needs are less extreme, sleeping bag liners can be a good solution. Liners fit inside your sleeping bag and add 5 to 25 degrees to the temperature rating. A popular solution is to buy a three-season bag, those rated between 10F to 32F, and add a liner for winter camping. Three-season bags are a good compromise for use in summer conditions and are warm enough that adding a liner allows them to be used in moderate winter conditions.

compact sleeping bag montbell

Packed 20-degree down sleeping bag

How does dead space affect warmth in a sleeping bag?

Dead space affects the warmth in a sleeping bag by allowing your body to heat a layer of air between you and your bag. The loft of your bag traps this air and provides insulation to keep it warm. Too little dead space and you risk compressing the loft of the bag when wrapping it around yourself. Too much dead space and your body have to do extra work to heat up the space. If you're on the fence, err on the side of being too big. You can always stuff an extra piece of clothing in your bag if there is too much dead space.

Do sleeping bag degree ratings account for the clothes you may be wearing?

Sleeping bag degree ratings account for one layer of thermal underwear plus the warmth of the sleeping bag. It’s important to know what type of rating the tag is describing. If it’s rated for “lower limit” this is the temperature a male can sleep uninterrupted for 8 hours in a curled position. “Comfort” is the temperature a female can comfortably sleep in a relaxed position. Less commonly used are “upper limit”, the temperature a male can sleep without sweating, and “extreme” the minimum temperature a female can survive for 6 hours in.


📸 Some photos in this post were taken by Ross Enlow (@rossaenlow) and Jonathan Davis (@meowhikes)

Justin Sprecher photo

About Justin Sprecher

Justin is a thru-hiker and writer with a passion for wild backcountry. He's thru-hiked the Pacific Northwest Trail, LASHed the Great Divide Trail and Arizona Trail, and clocked up 1,000s of miles on long-distance trails around the world.

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After thru-hiking the Appalachian Trail, Chris Cage created Greenbelly to provide fast, filling and balanced meals to backpackers. Chris also wrote How to Hike the Appalachian Trail.

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