The best ultralight sleeping bags

Therm-A-Rest is known for making top-quality sleeping pads, and the Hyperion 32 is a great mate to its NeoAir XLite sleeping pad, which I’ve used for years. Like other top-end makers, Therm-A-Rest uses the latest in material technology to provide an exceptionally light and packable bag. It’s warm enough for late spring, summer, and early fall use, and users should note that the bag is comfort rated at 41F and marketed as a 32F bag. The bag is filled with 8.5 ounces of 900 power fill down — the best on the market. The bag lofts quickly and uses box baffle construction to keep the down fill where it needs to be to avoid cold spots and keep you warm. To maximize warmth and save weight, the designers put 70 percent of the insulation on the top of the bag and 30 percent on the back. This may be an issue for side sleepers. The hood of the bag is cinchable and has a nice draft collar. The snag-resistant two-way zipper runs just over half the length of the bag. While it saves weight, it also prevents the option of ventilating the bag below the knee. Therm-A-Rest also ingeniously integrated two removable sleeping pad straps that keep you from sliding off your sleeping pad in the middle of the night. Genius!

Remarkably, this bag is one of the lightest on the market, and Therm-A-Rest shaved ounces by making the bag very form-fitting. I’m 6-foot-3 and tested the long variant of the bag. I felt snug but not overly constrained in the bag. The footbox was roomier and more comfortable than my current UL sleeping bag, the Marmot Hydrogen 30 bag. With the help of a well-designed lightweight stuff sack, it packed down incredibly small — just a bit larger than a one-liter Nalgene bottle. This is a high-quality, high-performance, two-season bag for fast and light missions. It also comes in a 20F variant.

My very first sleeping bag was a synthetic insulation 30F made by Sierra Designs. I love this bag even more. First, because of its design and use of high-quality 800 power fill down, it compresses down to about one-third of my old synthetic bag and weighs pounds less. The shell of the bag is durable 15D water-repellent ripstop nylon and the lining is also 15D nylon. The mummy cut of the bag and baffle design reduce weight and also makes the bag more thermally efficient.

One of the tradeoffs of this bag is that the designers built it with a half-length zipper to reduce weight, but this decision also limits some versatility in ventilation below the waist. Sierra Designs did find a lightweight and creative solution to lower body ventilation by designing a self-sealing foot vent, which adds a bit of weight, but I think it’s worth it for the increased versatility in venting. The zipper does have a large hanging draft tube to keep out cold air and also features anti-snag material along its run.

The bag weighs in at a pound and a half and the non-compressible stuff sack is about 13 by seven inches. I highly recommend getting a compressible stuff sack to further reduce the mass of this bag to increase packability. If you feel restricted in mummy bags, consider Sierra Designs’ Nitro Quilt 35 at 22 ounces (620 grams) and $249 — essentially an oversized down comforter in ripstop nylon.

The Magma is REI’s top-end ultra lightweight series of sleeping bags. It comes in 30F and 15F versions. The Magma 30 features a high-tech 15D Pertex shell, supple 15D nylon lining, and is sandwiched between almost 10 ounces of high-quality 850 fill power down. It’s cut a bit more roomier than many UL bags, especially at the knee and foot. Starting at the top, the contoured hood is more form-fitting than most and features two different hood drawcords to allow you to dial in comfort. The insulated collar yoke is generous and prevents cold drafts at the neck and shoulder.

Unlike many UL bags, the Magma features a full-length zipper that allows for more ventilation options at the cost of a few more grams. They’ve redesigned the zipper cover and added an internal anti-snag strip to keep the nicely designed zipper pull from fowling. The design of the zipper allows for fast and easy unzipping, which is key when you need to pee in the middle of the night. The bag also features a zipper pull garage to prevent it from bothering your face. Variable baffle spacing helps eliminate cold spots and keeps the down fill from shifting around.

My only gripe about this bag is that it is marketed as a 30F bag but really has a 39F comfort rating, so it should be marketed as a 40F bag. It could benefit from another ounce or two of down. Also, it doesn’t come with a compressible stuff sack.

A favorite among long-distance backpackers, this ultra-lightweight and exceptionally packable sleeping bag leverages high-tech materials and a narrow cut to keep weight at a minimum. The bag is warm and filled with 10 ounces of 850 fill down. The 10D ripstop nylon with DWR finish top fabric feels good to the skin. And we really appreciated the super smooth snag-proof light-weight zipper design with a full vertical hanging baffle to keep drafts from passing through. Mountain Hardwear also placed a one-inch strip of textured fabric along the zipper length to prevent snagging. The top of the bag has a cinchable four-chamber hood (not all ultralight bags do), a smallish draft collar, and a zipper garage to keep the nicely finished zipper pull from irritating your face. At the other end of the bag, the ergonomically designed footbox is comfortable and warm. The entire length of the bag is tuck-stitched and baffled to keep the down fill in place and minimize the potential for cold spots. Missing from this bag is a zippered pocket on the interior of the bag for small items like cell phones.

Burlier folks will want to try this bag before committing as the cut is narrow — a weight-saving trade-off. Some larger users complained they felt overly constrained. I did not. I’m 6-foot-3 and 215 pounds and felt a bit tight in the bag, but not uncomfortably so. It’s a performance mummy bag, dummy! Less material is less weight, and less volume is less air for your body to heat. I’d definitely pack it. Speaking of packing, this bag packs down incredibly small, about the size of two one-liter Nalgene bottles. It comes with a nice lightweight nylon compression sack and a large mesh storage sack. The Phantom is available in 30F, 15F, 0F, and 30F Alpine variants.

I’ve used Sea to Summit’s dry bags for decades, and this was the first sleeping bag of theirs I have tested. The Spark is actually a series of similarly designed bags in 40F, 28F, 18F, and 5F options in both regular and long sizes. First, this bag is made from quality materials. The Spark series is made from 10D ripstop nylon on the shell and soft 7D nylon on the interior, which feels really good on the skin. In between is 850 power fill ultra-dry (hydrophobic) down that will help the down stay lofty in humid conditions.

So what do I like about this bag? I really appreciated some of the innovative design features of the Spark 28. For instance, this bag uses vertical baffles on the body and horizontal baffles on the legs and feet. This design will help keep side sleepers warmer because the vertical baffles on the body prevent the down from slipping down to the sides of the bag.

The ergonomic footbox also allows your feet to move at night without feeling constricted. It also has a nice zipper guard made from more rigid nylon to help prevent snagging. I’m 6-foot-3 and opted to test the men’s long version. I found it form-fitting but not uncomfortably snug. The Spark 28 also has a nice cinchable hood with a cinchable draft collar. Lastly, Sea to Summit has a wonderful lifetime warranty for this product.

What I don’t like about this bag? First, the baffles are sewn through instead of box baffles, which leads to more cold spots. (The 40F and 28F are sewn through and the 18F and 5F bags have box baffles.) Also, some users have reported they found the YKK #3 zipper is a bit finicky and hard to reach and unzip when inside the bag. I wish the draft tube along the zipper was a bit larger to provide more coverage, as well.
Also to note, the cinch for the hood and neck baffle are on the same paired drawstrings, which makes it a bit more difficult to adjust if you want a tighter hood and looser neck baffle or vice versa.

To be considered ultralight, a sleeping bag’s weight really should weigh in at 25 ounces or less. The Mountain Hardwear Bishop Pass 30 weighs 28 ounces, but I just couldn’t resist bringing it to your attention since it’s a great bag at a great price and pretty low weight. Sure, it’s not a 9.8-ounce Patagonia, but it’s also a lot warmer — so you won’t freeze your gonads off. The Bishop Pass 30 is Mountain Hardwear’s value bag. It doesn’t have the same high-tech features as the Phantom 30, but it’s solidly capable in its own right.

The Bishop Pass is a true 30-degree bag that is insulated with 12 ounces of 650 fill duck down and provides four inches of loft. The body fabric is made of 20D ripstop nylon with a DWR finish and it’s soft to the touch. Contributing to the bag’s weight is a more versatile full-length zipper that allows you to ventilate from both the torso and feet. Like the Phantom, it features a quality snag-proof YKK zipper pull, full-length hanging baffle, one-inch-wide anti-snag zipper lining, and a zipper pull garage near the collar for added comfort. The performance mummy cut is a bit roomier than the Phantom, but it’s efficient. The three-baffle hood is cinchable and features a down-filled face gasket around the collar. On the interior of the bag is a small Velcro-closed pocket to stow small items. The bag also has six hanging loops — two each at the foot, knee, and shoulder. The stuff sack is unremarkable and doesn’t have cinch straps, which makes the bag less packable than I’d prefer.

Just for fun, I stuffed the Bishop Pass into the Phantom’s stuff sack, cranked down the compression straps, and achieved nearly the same sized mass. Definitely invest in a compression stuff sack for this bag. This bag is a great value-buy, delivering true 30F warmth. It’s 6.3 ounces heavier than the Phantom and also $185 less, so you’re paying about $30 less per ounce than the Phantom and getting fairly similar warmth and greater durability. If cost is a concern, this is a great option.