ultralight sleeping bags

Best Ultralight Sleeping Bags of 2021

Backpackers beware! Most sleeping bag temperature ratings are exaggerated by at least 10 degrees! You won’t sleep one wink in a 20° bag on a 20° night. That’s because the number in a bag’s name refers to the lowest possible temperature at which a person could conceivably fall asleep, far lower than the temperature at which 99% of people could actually fall asleep. What’s more, ratings are often inflated or rounded favorably by manufacturers incentivized to offer the most competitive product specs.

Know the actual sleeping temperature of your sleeping bag

This is where we can help. This guide gives you an additional layer of product analysis/verification/buyer protection. Or to put it bluntly, we have a better comfort rating for sleeping bags. This is our proprietary sleeping bag warmth rating model, which is backed up by field and lab testing. It uses a multi-variable equation using the type and amont of down and the sleeping bag configuration to accurately predict the comfort temperature of a sleeping bag (or quilt) to better compare apples-to-apples (that is you can compare ISO tested bags with non-tested bags).

Which backpacking sleeping bags made the cut?

The best of the best sleeping bags, the ones in this guide, are designed intelligently, have high warmth-to-weight ratios, and are cost-effective — that is, they handily beat most competitor’s sleeping bags in these metrics. You will definitely notice that some revered, long time favorite sleeping bags and top picks in other guides did not make the cut. We have the data to backup why these sleeping bag’s warmth to weight and/or warmth to cost performance falls short of our top picks. See our Ultralight Sleeping Bag Ratings | Data Table.

Performance, Value, & Budget Sleeping Bags

To further ease buyers, we break our selection out into three price categories: Performance, Value, and Budget. While you’re here, don’t forget to check out our guide to the Best Sleeping Pads. Like bags, pads play a critical role in keeping you warm and comfortable at night.

Staff Quick Picks | Ultralight Sleeping Bags

For those short on time, here’s our take on the best of the best backpacking sleeping bags

Best Performance Sleeping Bag: Zpacks Classic Sleeping Bag 20

Best Value Sleeping Bag: REI Magma 15

Best Budget Sleeping Bag: Mountain Hardwear Bishop Pass 15

Best Sleeping Bag for Restless Sleepers: Nemo Disco 15

Best Performance Sleeping Bags of 2021

3 Season with a Comfort Rating of Approx. +30° F

These are the best of the best; the sleeping bags that will keep you warmest for the lowest weight possible — and only a select few sleeping bags made the cut. These options are great for ultralight enthusiasts, thru-hikers, or any backpacker seeking the best possible gear available. These are the bags we recommend when weight and volume efficiency is a primary concern, and additional cost upfront is viewed as a long term investment.

Zpacks Classic Sleeping Bag 20

Top Pick | Best Overall Performance

17.3 oz | $359 MSRP
ISO tested comfort: n/a | Modeled comfort: +27 F
Warmth to weight: 5.1 | Warmth to cost: 3.1

The Zpacks Classic Sleeping Bag 20F has one of the highest warmth to weight ratings in this guide while still remaining a good value. What we really like about the Zpacks Classic Sleeping Bag is that it combines the best attributes of a quilt and a sleeping bag. It has the weight of a quilt and can be used unzippered, just like a quilt. But when it gets cold you can zip it up into a draft-free, sleeping bag mode. In normal Zpacks fashion, it uses the lightest material options – 900 fill power down and a lighter 7D nylon shell. Those materials come at a price making them more expensive than most camping quilts, but less expensive than most sleeping bags. Note that this sleeping bag is hoodless. As such, on super cold nights, you’ll need to use it with a warm hat — to our minds, not a big deal, and it has significant advantages for side-sleeping.

Do you sleep warm or need a lighter bag? The Zpacks Classic 30 is also our pick for warm weather or people. The sleeping bag-quilt hybrid model allows for extra venting.

BEST FOR: Those who want one of the very lightest and warmest backcountry sleeping options and who like the flexibility of using it as both a quilt and a sleeping bag!

NOT AS GOOD FOR: Campers that dislike a snug fit (although this has a zipper to solve that in all but very cold conditions) or hikers that abuse their gear (the 7D shell is relatively delicate).

Thermarest Hyperion 20

Top Pick | Best Conventional Sleeping Bag

20 oz | $420 MSRP
ISO tested comfort: +32 F | Modeled comfort: +32 F
Warmth to weight: 3.5 | Warmth to cost: 2.2

The Thermarest Hyperion 20F Sleeping Bag is one of the very lightest 32 degree comfort rated bags on the market. Not surprisingly, it has one of the best warmth-to-weight ratios of all the sleeping bags we compared in our model. This is achieved through the use of 900 fill power down, a relatively lightweight 10D shell fabric, and a snug fit. In addition, Thermarest states that they intelligently distribute the down in their bag so that 70% of the down is on the top section of the bag, this should in theory put more down where it is needed. We believe that is at least part of what allows Thermarest Hyperion 20F to be lighter than almost all similarly comfort temp rated bags. The pad strap system is helpful and not something you find on any other of the bags here with the exception of the Sierra Designs Cloud bags, and they are removable if you don’t want the minimal extra weight they add.

BEST FOR: Hikers who are willing to pay a modest premium to get one of the very lightest +32 F comfort bags available. (And it’s $100 to $200 less expensive than many better known and heavier sleeping bags).

NOT AS GOOD FOR: Hikers who don’t like narrow bags and are allergic to high prices. Also worth noting is that 10D shell fabric requires reasonable care in the field.

Sea to Summit Spark 18 (Men’s)

Top Pick | Roomiest Ultralight Bag Men's & Women's

23.5 oz | $499 MSRP
ISO tested comfort: +29 F | Modeled comfort: +30 F
Warmth to weight: 3.4 | Warmth to cost: 2.2

The Sea to Summit Spark / Flame series is a brand new, ultralight and high performing series in their popular line of sleeping bags. This series focuses on using the highest-end materials and minimalist design in order to shave weight wherever possible. Because of this, these are more expensive than many comparable bags. Though they offer these models in a range of temperatures, we highlight the 18-degree limit rating (30 degree comfort) because we find this temperature to be the sweet spot for most three-season backpacking and camping trips. Sea to Summit uses a 10D shell with a 7D liner to decrease pack size and weight. Furthermore, the 18 degree model is still fully baffled on the inside and has a full-length zipper for added versatility when it’s warmer outside.

BEST FOR: Hikers who are willing to pay a pretty penny in order to get one of the very lightest +29 F comfort bags available. There is also a modest amount of room in the bag.

NOT AS GOOD FOR: Hikers who are looking for a value option or want a bag that can withstand abuse.

Sea to Summit Flame 15 (Women’s)

31.4 oz | $549 MSRP
ISO tested comfort: +15 F | Modeled comfort: +16 F
Warmth to weight: 4.3 | Warmth to cost: 3.3

Women sleep colder than men (about 10 degrees colder). As such, the Sea to Summit Flame series of Women’s sleeping bags is temperature rated for Women while still being light! Bravo Sea to Summit! Our pick is the Sea to Summit Flame 15 Sleeping Bag because we feel it will allow most women to sleep comfortably to around freezing — the sweet spot for most three-season backpacking and camping trips. Sea to Summit uses a 10D shell with a 7D liner to decrease pack size and weight. Furthermore, the 15 degree model is still fully baffled on the inside and has a full-length zipper for added versatility when it’s warmer outside.

Note that the the Sea to Summit Spark / Flame series a brand new, ultralight and high performing series in their popular line of sleeping bags. This series focuses on using the highest-end materials and minimalist design in order to shave weight wherever possible. Because of this, these are more expensive than many comparable bags.

BEST FOR: Women hikers that want to sleep warm to around freezing and who are willing to pay a pretty penny in order to get one of the very lightest bags available. There is also a modest amount of room in the bag.

NOT AS GOOD FOR: Hikers who are looking for a value option or want a bag that can withstand abuse.

What happened to traditional favorite sleeping bags?

Like Western Mountaineering Ultralite and Summerlite?

Yup, many of these are still decent bags. But they most often missed making the top picks by a lower rating for warmth/weight and or warmth/cost or possibly another reason. Finally, we felt some of these bags were simply too expensive to make our top picks in comparison to the far less expensive options with better/similar performance included in our review. See our Ultralight Sleeping Bag Ratings | Data Table

Best Performance Sleeping Bags for Colder Temperatures (or people that sleep cold)

Below are a few of the very lightest weight options for folks that need to comfortably camp at below freezing temperatures, or those that just can’t seem to sleep warm in most “3-season” sleeping bags. Here our criteria is a bag with a Comfort Rating of Approx. +20° F. Add a nice down jacket and you can likely sleep at even colder temperatures.

Zpacks Classic Sleeping Bag 10F

Top Pick | Best for Cold Sleepers

21.7 oz | $379 MSRP
ISO tested comfort: n/a | Modeled comfort: +23 F
Warmth to weight: 5.5 | Warmth to cost: 4.0

The Zpacks Classic Sleeping Bag 10F is a warmer version of their 20F bag — an incredibly light option for cold sleepers! What we really like about the Zpacks Classic Sleeping Bag is that it combines the best attributes of a quilt and a sleeping bag. It has the weight of a quilt and can be used unzippered, just like a quilt. But when it gets cold you can zip it up into a draft free, sleeping bag mode. In normal Zpacks fashion it uses the lightest material options – 900 fill power down and a lighter 7D nylon shell. Those materials come at a price making it more expensive than most camping quilts, but less expensive than most sleeping bags. Note that this sleeping bag is hoodless. As such, on super cold nights, you’ll need to use it with a warm hat — to our minds, not a big deal, and it has significant advantages for side-sleeping. In summary, this is an amazing cold weather option for backpackers who may be unsure about using a full quilt, yet want the weight savings of these lighter sleep systems.

BEST FOR: Those who want one of the very lightest and warmest backcountry sleeping options and who like the flexibility of using it as both a quilt and a sleeping bag!

NOT AS GOOD FOR: Campers that don’t like a snug fit (although this has a zipper to solve that in all but very cold conditions) or hikers that abuse their gear (the 7D shell is relatively delicate).

Sea to Summit Spark Ultralite 4 5F

31.0 oz | $549 MSRP
ISO tested comfort: +18 F | Modeled comfort: +18 F
Warmth to weight: 4.0 | Warmth to cost: 3.0

The Sea to Summit Spark Ultalight 4 (+ 5F) sleeping bag is a great lightweight option when the temperature drops. We find its +5 F degree limit rating (+18 F degree comfort rating) will allow most folks to sleep well below the usual near freezing temps ratings of our three season picks — add a down jacket and you can go even lower. Sea to Summit uses a 10D shell with a 7D liner to decrease pack size and weight. Furthermore, it’s still fully baffled on the inside and has a full-length zipper for added versatility when it’s warmer outside.

The Sea to Summit Spark / Flame series is a brand new, ultralight and high performing series in their popular line of sleeping bags. This series focuses on using the highest-end materials and minimalist design in order to shave weight wherever possible. Because of this, these are more expensive than many comparable bags.

BEST FOR: Hikers who are willing to pay a pretty penny in order to get one of the very lightest below freezing temperature bags available. There is also a modest amount of room in the bag.

Best Value Ultralight Sleeping Bags of 2021

For most people, a good value proposition is more important than finding the lowest possible price tag or the most technologically advanced option. We determine the value of each sleeping bag by comparing its warmth to weight to price. The following options are best for those who don’t mind investing in a high-quality product but don’t want to break the bank.

REI Magma 15

Top Pick | Best Value Sleeping Bag

28 oz | $389 MSRP
ISO tested comfort: +28 F | Modeled comfort: +29 F
Warmth to weight: 3.0 | Warmth to cost: 2.9 (~3.9 when on sale!)

Our pick for a Value Sleeping Bag: The REI Co-op Magma 15 one of the best sleeping bags in the under $400 category and under $300 on sale making it an insanely good deal! the REI Co-op Magma 15 Sleeping Bag M’s & W’s is a good blend of both cost/warmth and weight to warmth — placing solidly in both measures. In particular it’s one of the better values in a ~+30 comfort rated sleeping bag, and that’s when not on sale. As such, the REI Co-op Magma 15 is a great all-around 3-season choice for many campers, allowing you to go light without going broke. And of course it’s backed by REI.

BEST FOR: Hikers wanting a full featured sleeping bag comfortable to around freezing that’s light but not excessively expensive. Readily available.

NOT AS GOOD FOR: Hikers who dislike the tightness of a mummy bag as the leg area of the Magma is quite narrow. Hikers that must have the very lightest sleeping bag and are willing to pay for it.

Sierra Designs Nitro 20

Runner Up | Best Value Sleeping Bag

28.0 oz | $320 MSRP
ISO tested comfort: +28 F | Modeled comfort: +28 F
Warmth to weight: 3.0 | Warmth to cost: 3.5

The Sierra Designs Nitro 20 mummy sleeping bag is a fully featured, relatively inexpensive sleep system that is great for three-season use. Sierra Designs uses 800 fill-power PFC Dri-down in combination with 15D nylon liner and outer shell, which shaves weight. Though neither of these features are the lightest possible, they are quality and will hold up over time. They also use 5 inch baffle spacing on the side walls to keep down from shifting around, which keeps cold spots away. It may take some work to get the bag stuffed down as small as advertised (a gallon of milk), but it does compress fairly easily. The 62 inch shoulder girth gives a decent amount of room to move around, though the mummy design of the bag gets fairly narrow towards the foot and leg area.

BEST FOR: Hikers wanting a full featured 3-season (around freezing) sleeping bag without breaking the bank. The 15D fabric is also fairly tear and snag resistant, so it’s good for hikers who aren’t super careful with their gear.

NOT AS GOOD FOR: Hikers who dislike the tightness of a mummy bag; the leg area is fairly narrow.

Best Budget Backpacking Sleeping Bags of 2021

This category includes a range of the best sleeping bags for under $300. While this may not seem budget-friendly up front, consider that a good sleeping bag will last you for many years. Consider also what happens when brands cut too many corners with cheaper bags – you get cold and can’t sleep. Even in the budget category, we won’t recommend sleeping bags we wouldn’t use ourselves.

Mountain Hardwear Bishop Pass 15

Top Pick | Best Budget Sleeping Bag

37.4 oz | $240 MSRP
ISO tested comfort: +26 F | Modeled comfort: +28 F
Warmth to weight: 2.5 | Warmth to cost: 5.1

For a bit over a kilo, the Mountain Hardwear Bishop Pass 15 is a reasonably priced, excellently performing three-season sleeping bag. This is one of our highest performing warmth to cost bags, and one that we highly recommend if you don’t mind carrying a pound of extra weight . Mountain Hardwear uses 650 fill-power down and a 20D nylon shell, which are not the lightest weight materials but it helps cut costs and also makes the bag very resistant to tears and snags. With a +26 comfort limit, this bag will perform in most three-season conditions or even a bit colder, especially with a warm sleeping pad and clothing. There’s a full length draft tube down the zipper to prevent heat loss in this area, as well as an internal stash pocket (a feature we don’t see often but love!).

BEST FOR: Hikers who want a solid three-season bag without breaking the bank. This bag doesn’t have to be babied, and is a fantastic value choice.

NOT AS GOOD FOR: Hikers who want to shave weight on their pack or don’t like a mummy design on a sleeping bag.

Best Sleeping Bags for Restless Sleepers & Side Sleepers of 2021

This is a relatively new category of ultralight sleeping bags designed to be a lot more comfortable and user friendly for restless sleepers and the large number of people that sleep much of the time on their sides. These bags while a bit heavier than a conventional mummy bag, are also a bit less expensive using more economical materials like 650 fill power down and even a touch of synthetic fill in key areas.

Nemo Disco 15

Top Pick | Best for Restless Sleepers

43.0 oz | $300 MSRP
ISO tested comfort: +25 F | Modeled comfort: n/a
Warmth to weight: 2.2 | Warmth to cost: 4.3

Nemo’s Disco 15 has a unique design well-suited for those who toss and turn, or like to spread out their limbs while they sleep. As opposed to a mummy bag, the Disco is spoon shaped. This means there’s extra room at the elbows and knees, for sleepers to shift around or get onto their sides. Furthermore, there are gills for venting down the front of the bag to release body heat on warmer nights. These two features make this a much more valuable bag for summer and shoulder season trips, where conserving body heat is not the top priority. There’s also a pocket to slip in a backpacking pillow. Another plus, with a +25 comfort limit, this bag will perform in most three-season conditions or even a bit colder, especially with a warm sleeping pad and clothing. And, if anything goes wrong, Nemo covers this bag under their lifetime warranty.

BEST FOR: Hikers who want extra room to move around while sleeping and who occasionally feel constricted in a mummy bag. Also, those who prioritize comfort over weight.

NOT AS GOOD FOR: Hikers who are looking to travel as light and fast as possible.

Big Agnes Sidewinder SL 20

Top Pick | Innovative Option for Side Sleepers

36.0 oz | $280 MSRP
ISO tested comfort: +25 F | Modeled comfort: n/a*
Warmth to weight: 2.1 | Warmth to cost: 3.6

The Big Agnes Sidewinder is a new product designed specifically for side sleepers. If you like to toss and turn and settle into position on your side, a mummy bag may tend to feel constricting and uncomfortable. Big Agnes uses a down/synthetic blend in their bag, in order to maximize comfortable loft as well as synthetic insulation in strategic locations. The footbox, mummy hood, and insulation mapping are all designed for rolling from one side to the other. This bag is comfort rated to 30-degrees Fahrenheit, so it’s great for most three-season adventures. Furthermore, a sleeping pad sleeve on the bottom ensures that it stays in place all night.

*Because this bag uses down and synthetic fill (650-fill-power DownTek combined with FireLine ECO synthetic insulation), it does not work in our model for a predicted comfort temperature. Therefore, we recommend you follow the ENO/ISO Comfort Rating for the bag.

BEST FOR: Hikers who want extra room to move around while sleeping and who occasionally feel constricted in a mummy bag. Also, those who prioritize comfort over weight.

NOT AS GOOD FOR: Hikers who are looking to travel as light and fast as possible.

ultralight sleeping bags for backpacking

Conclusion

Don’t let a bad night’s sleep ruin a long awaited backpacking trip. We’ve all been there, and losing a night (or more) of restful sleep can give you the wrong impression of what cold weather camping is actually like when properly equiped. Often times, confusion and misinformation happens because of misleading temperature ratings fed to customers by eager brands competing to sell you the cure for a bad night’s sleep. In this guide we thoroughly outlined how temperature ratings work, and provided a solid understanding of how *actually* warm each of these products are.

We’ve selected a range of bags to fit different campers’ priorities. Including warmth to weight and warmth to cost categories ensures that you pick the right product for your specific needs and sleeping style. Now, armed with this information and our top picks for sleeping bags this year, you’re ready to shop with confidence as you plan next year’s trips.

Ultralight Sleeping Bag Ratings | Data Table

Disclaimer

This post contains affiliate links. If you make a purchase after clicking on the these links, a portion of the sale helps support this site at no additional cost to you. I do not receive compensation from the companies whose products are listed. For product reviews: unless otherwise noted, products are purchased with my own funds. I am never under an obligation to write a review about any product. Finally, this post expresses my own independent opinion.

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