Save Weight in Your Pack With These Ultralight Sleeping Bags for Thru-Hiking, Bikepacking, and Camping

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Backpacking, bikepacking, and lengthy hikes require compact and airy products to lighten the load and make treks bearable—but these days, you don’t have to sacrifice warmth or comfort. Regarding overnights in the outdoors, you’ll need a sleeping bag, preferably one that compresses down to save room for camping snacks or hiking socks.

The best ultralight sleeping bags weigh less than 2 pounds and are ultra compact with easy packing systems. They’re also made with lofty down fill or synthetic insulation that springs into place when you unpack your bag but squashes down when it's time to hit the trails.

Finding a reliable ultralight sleeping bag is a daunting task with so many outdoor products on the market. We’ve rounded up the best according to critical and user reviews, as well as personal hands-on time, for warm, cozy nights in the great outdoors.

Need more outdoor gear for your outdoor escapades? Check out our picks for the best solo tents, family-sized tents, and gifts for adventurers.

The Best Ultralight Sleeping Bags

• Best Overall: Rab Mythic Ultra 180

• Best Value: REI Co-op Magma 30

• Most Affordable: Kelty Cosmic 20

• Best for Bikepacking: Western Mountaineering Flylite

• Best for Warm Weather: Marmot Micron 40

What to Consider

Weight

Ultralight sleeping bags weigh about 2 pounds and compress into small sizes to occupy as little space as possible. The low weight of these sleeping bags generally correlates with the cost. So if you’re not looking to spend a few hundred dollars on a new bag, opt for a slightly heavier one to save money.

If you need a thru-hiking bag, lean toward one that can fit into a small stuff sack. Most ultralight bags come with their own, so you can stow the sack in a backpack pocket or dangle them from a carabiner (if you’re brave enough to taunt the weather on an overnight hike). The bags are usually tapered dramatically at the feet to save on weight, and to make you extra warm by keeping the insulation close to your body.

You can afford to skew heavier if you’re just hoping to lighten your load-out when car camping or packing for a single overnight hike. Plenty of bags that weigh 4 pounds or less are plenty light for these purposes, and they save costs at the expense of a bit of extra weight—but if you’re going to be thru-hiking for several days or weeks, the lighter, the better.

Note that some cheaper options don’t include stuff sacks or other compact-friendly features.

Warmth Rating

Not all sleeping bags are built for all-season use. To consider what climates a sleeping bag is best in, check its temperature rating. This indicates the lowest tested temperature at which the bag can keep the average person comfortable.

Most sleeping bags show their temperature rating directly in their product name. For example, Big Agnes’s Pluton 40 suits temperatures down to 40 degrees Fahrenheit. Some brands offer the same model in various temperature ratings, which is the case for the Sea to Summit’s Ember Down Quilt, available for temps as low as 50, 35, and 25 degrees. Generally speaking, the lower the temperature rating, the higher the price.

Down Fill

Fill power indicates the quality of down (usually light, fluffy clusters of ducks or waterfowl) inside of a sleeping bag or coat. Down is a natural, lightweight, and breathable material that allows birds to warm themselves—and it makes great insulation for humans, too. The fill power number conveys how many cubic inches of insulation 1 ounce of that down fill produces. For the purposes of sleeping bags, the higher the fill number, the better the insulation.

It’s important to note that down compresses and packs down better than synthetic insulation, but synthetic insulation still warms even when it gets wet—down does not. If your sleeping bag is made with synthetic materials, it may lack the springiness of natural down and offer less warmth in extreme temperatures than the natural stuff. Moreover, synthetic insulation is often heavier than down. That said, plenty of synthetic options, like PrimaLoft, are perfectly acceptable for the average outdoors enthusiast.

Materials

Sleeping bags are made with nylon or polyester—or sometimes a blend of both—as they’re durable and water-resistant. Shells are also often treated with a durable water repellent, or DWR, finish to further protect against moisture. Synthetics have moisture-wicking and insulating properties, making them versatile for a range of conditions.

Synthetic fabrics used for outdoor gear are often ripstop, a textile weaving technique that provides materials with abrasion resistance. Ripstop fabrics have a visible grid-like pattern of thick, reinforced threads that protect against snags and scratches—sort of like wired glass. While ripstop doesn’t make a piece of clothing or gear invincible, it certainly helps lengthen the lifespan of a product and prevents ripping open your sleeping bag with your camping knife or a sharp tree branch.

How We Selected

To identify the best ultralight sleeping bags, relied on personal testing experience (Which sleeping bags is our staff familiar with? What brands do we love?), trying a few out for a few nights in the woods, and analyzing materials and accessibility. We also considered frequently recommended products from camping subreddits and buyer’s guides by authorities in outdoor equipment. We found the best ultralight sleeping bags across a range of budgets, temperature ratings, weights, functions (hoods, ventilation, interior pockets), and materials.

Mythic Ultra 180 Ultralight Sleeping Bag

At 14.1 ounces, Rab’s Mythic Ultra 180 is the lightest sleeping bag on this list. It’s also the most expensive.

The 7-denier shell and liner help cut down on weight where it matters, while its down is finished with a hydrophobic treatment that helps retain its loft should it take on moisture. The Mythic Ultra 180 also uses heat-reflective technology, accomplished by coating each fiber in titanium, thus bouncing a user’s warmth inside the sleeping bag and retaining heat longer.

This ultralight sleeping bag stuffs into a cotton sack when not in use, which may be a turn-off for those who look for mesh to air out their bags. It may be overkill for those looking for a casual car camping bag, but its incredible components, chunky collar, and oversized hood are enough for ultralight mountaineers and light backpackers.

Unisex Magma 30 Ultralight Sleeping Bag

REI Co-op’s Magma 30 sports a fitted, mummy-style silhouette with plenty of knee and foot space and a contoured hood that leaves space for a pillow.

Sitting in the middle of our cheapest and most expensive options, the Magma 30 has a durable, water-resistant lining stuffed with 850-fill-power goose down. Its foot box can also accommodate large feet. As of spring 2024, REI has made the Magma 30 a unisex sleeping bag, giving you several options for sizes, including wide and narrow fits and short and long lengths.

Packed up and compressed, this sleeping bag stuffs into a 2.6-liter sack and weighs roughly 1 pound and 8.4 ounces, depending on length and size. Users love previous models of this bag for its weight, price, and shell material, which one REI customer calls “soft and silent.” Some say, however, the Magma 30 is best fit for 40-degree weather and is great for warm sleepers.

The Magma 15 is also available for colder nights at an extra $50 and a few more ounces.

Shop Magma 15

Cosmic 20 Ultralight Sleeping Bag (Men’s)

Kelty’s Cosmo 20, at less than $200, is one of the cheapest ultralight sleeping bags. Available in regular, long, and short lengths, this 550-fill-power down bag has a draft collar and a hood to keep cold air out and a roomy foot box to allow air to circulate between your toes. It also has a zippered stash pocket to store your book or headlamp while you sleep.

The 20-denier nylon shell and 50-denier polyester liner give it heft compared to other bags on this list, making it heavier at 2 pounds and 7 ounces. But users love this product for its no-frills design and straightforward mummy silhouette, saying it’s well worth its budget price and it keeps you warm.

Shop Women’s Shop Cosmic 0

Flylite Ultralight Sleeping Bag

A frequent recommendation for those who go bikepacking during the warm months, the Flylite sleeping bag is a supremely lightweight quilted bag that tightly packs down for stowing on your bike’s rear rack or pannier. (One critic review says it packs down to the size of a Nalgene.) Its zipper goes down to the toe box, so you can ventilate your feet and stay comfy, and its down is warm enough for cool nights. Although it’s rated for three seasons, many critic reviews say it’s best for two—spring and summer.

It’s fairly pricey, but if you can swing the Flylite, it’ll do you good on your next tour, taking up minimal space. Some reviews say it requires constant readjusting, however, as the inner down clusters easily shift out of place within the baffles, which can create cold spots.

Micron 40 Ultralight Sleeping Bag (Men’s)

At under 1 pound, the Micron is exceptionally lightweight and comes with a sack that further compresses the sleeping bag. It’s great for staying warm on cool nights, but if you get too toasty you can release heat by opening its side zipper, which starts from the bag's head, crosses the foot box, and rounds to the other side. Fully unzipping also converts it into a flat blanket.

A DWR-coating helps with water resistance, and two hang loops make air-drying a cinch. An internal stash pocket lets you pack away small goods, too, like a phone or a flashlight. Plenty of reviewers online say it’s smartly designed and of excellent quality.

If you’re looking for warmth in case things get unexpectedly cold, note that this bag doesn’t include a hood, which will leave your head exposed.

Pluton 40 UL Ultralight Sleeping Bag

The Pluton 40 is an ultralight, highly compressible sleeping bag that packs down into a stuff sack that’s just 5 by 6 inches. It’s also the quietest on this list, with many critical reviews pointing out that its materials barely make a sound when they roll around or unravel the bag. This is great for those who move a lot at night.

The bag is made with 850-fill water-repellent down, which, along with the cinched hood that wraps around your head, keeps you warm. Best of all, the two-way zipper lets you close the hood as you fall asleep and open it back up for temperature regulation as needed.

Puffer Blanket

Nomadix makes versatile insulated blankets that also work as sleeping bags and cloaks, thanks to snap-button closures. They’re also super lightweight at just 2 pounds, with a stuff sack that packs down to 14 by 6 inches.

Although these aren’t traditional sleeping bags you can crawl into, they present a solid alternative for warmer nights and daytime naps during a camping trip.

These customer-favorite blankets are sand- and water-resistant, made with recycled polyester, and available in various colors and patterns. Without much fluff and fill compared to the true bags on this list, the Puffer is an excellent option for casual car campers who want to pack light. However, don’t expect it to be as tough or warm as a traditional sleeping bag.

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