Therm-a-Rest Ohm 20 Degree Sleeping Bag Review

For the last couple of years, I’ve only used quilts for backpacking. Once I transitioned, I couldn’t get enough of the extra room, versatility, and weight savings that I get with a quilt. When asked to review Therm-a-Rest’s new 20-degree sleeping bag, I closely reviewed the product’s specs and features first. I was immediately impressed. Even in the long version, the Ohm is even lighter than my 20-degree quilt, has about the same packed size, and packs a ton of features that make it a strong competitor in the highest echelon of ultralight sleep systems.

The Therm-a-Rest Ohm is an incredibly versatile ultralight sleeping bag. The regular version weighs just 1 lb 6 oz, and it packs down to roughly the size of a Nalgene. My biggest fear was sacrificing space and comfort while snoozing, but there is actually quite a bit of room in the hips and shoulders. Furthermore, for warm nights, the zipper extends all the way down through the footbox so you can fully open it into a quilt. In my opinion, albeit expensive, this bag is much more versatile than many competing ultralight sleep systems.

Therm-a-Rest Ohm At a Glance

• MSRP: $460 (regular) / $490 (long)
• Weight: 22 oz (regular) / 25 oz (long)
• Down fill: 900 Fill Goose Nikwax Hydrophobic Down RDS
• Comfort / lower limit: 32F / 20F
• Shell/lining fabric: 10D nylon ripstop with DWR / 10D nylon ripstop
• Packed Size: 6.5 in x 8 in

Circumstances of Review

I tested the long version of the Ohm for the last few months of Utah shoulder season on a wide variety of different adventures. In the spring, I took it on an overnight backcountry ski trip and car camping in the desert. Now that the snow has (mostly) finally melted in the Wasatch range, I’ve been able to test this bag on a couple of overnights in the mountains. I’ve used it across a range of temperatures, from lows below freezing to waking up to a balmy 70-degree morning. Its versatility has made it an excellent new addition to my pack during these varied weather and multi-sport months.

900 Fill-Power Goose Down

A large reason why this bag is so lightweight, packable, (and expensive) is because of the quality of down insulation used. In short, sleeping bags and quilts that use this quality of down are lighter because less insulation is needed. The individual down plumes trap more air between one another, which keeps your warmer. So, a sleeping bag with 600 fill-power down will have to use more insulation (adding weight) than a 900 fill-power bag. In addition to weight savings, it also compresses extremely well.

Sleeping bags and quilts that use 900 fill-power insulation are the lightest and most packable options available. Because of this, they are also the most expensive. In my testing, I’ve been extremely happy with how well the Ohm lofts up out of the compression sack and then compresses again the next morning. I’ll be sure to store it long-term in a larger sack so it retains its lofting power over time.

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My Favorite Features

• Packed size: When I take my time to stuff and fully compress this bag, it’s about the size of a Nalgene. It can fit just about anywhere in my pack, and I love having the option to keep it in my front mesh pocket to free up space inside. The 900 fill-power down does an amazing job of packing small while still lofting up immediately when it’s time to set up camp.
• Quilt convertibility: Something super unique about this product is how it fully converts into a quilt. Many ultralight sleeping bags have a zipper going only halfway down or to the foot box to save weight on the zipper. However, the Ohm has a zipper that wraps all the way down and around the foot box so it can fully transition into a blanket. This is great for thru-hikes, where you need a solid mummy bag that keeps you warm on cold nights but want the freedom of a quilt for cowboy camping in nicer weather.
• Weight: The Ohm rivals the weight of many competing ultralight quilts on the market. I have the long version, and it’s just a pound and a half. While you can find sleep systems for under a pound, these are usually much warmer bags/quilts or seriously sacrifice space and maneuverability.

Therm-a-Rest Ohm Pros

• Roominess. Transitioning from a quilt, I was worried about feeling claustrophobic in this bag. I have plenty of room to roll from side to side, and I especially love how the foot-box doesn’t feel too constricting. Plus, you can always pull the zipper all the way down and convert it into a quilt if you’re feeling especially restless on a certain trip.
• Warmth: The lowest temperature I encountered with this bag was 25 degrees Fahrenheit, and with my 4.0 r-value sleeping pad, I felt totally fine. I usually try to take a bag or quilt that’s rated for 10 degrees colder than the lowest temperature I’m expecting to encounter, but I wanted to push the limit for the sake of testing. With heavy socks, merino wool base layers, and a fleece on top, I was cozy well below freezing.
• Multiple uses: I really love quilts. I frequently bring them car camping or skiing because it’s so nice to have an extra down blanket handy. I expect to see more ultralight sleeping bags including this feature in the future.

Therm-a-Rest Ohm Cons

• Fragile shell/lining material. Most ultralight bags and quilts now use a 10D ripstop nylon material for the outer shell and inner lining. It is definitely necessary to baby the lining for this reason. Unfortunately, I ripped my quilt (with a 10D lining) just by pulling it too tightly while cowboy camping in the desert. To compare, some heavier bags use a 20D or 30D lining which improves the product’s longevity. I note this because if you’re a backpacker who frequently uses and abuses gear, it *may* be worth considering a custom quilt or bag with a 20D lining instead of 10D.
• No mummy hood. Because I choose to take this bag on colder trips, I wish there was a hood to fully wrap me in my down-filled burrito. However, leaving off this feature obviously contributes to how lightweight and packable the bag is.
• Price. The price tag on this bag is steep. Compared to many quilts with similar weight and warmth ratings, it’s substantially more expensive. However, you do get more versatility with this product than other competing lightweight sleeping bags or quilts.

Where I’m Taking the Therm-a-Rest Ohm

This is the perfect shoulder season bag. It’s a bit much for the warmer summer months, where I can get by with an even lighter quilt. When it’s in sleeping bag mode, it stays quite toasty and is a bit too hot for anything over ~50-degree nights. Though it does convert to quilt mode, without a zippered foot box, I’ve really only found that useful for warmer weather trips and wouldn’t use it that way during shoulder season.

I can’t wait to use this bag for some late summer and fall adventures I’m scheming in Idaho and Utah. It’s absolutely perfect for high alpine shoulder season, where you want consistent warmth without extra bulk or weight.

To Sum It Up

If it’s in your price range, I would highly recommend this bag for thru-hikers expecting to encounter a variety of temperatures on their trips. When fully zipped into a sleeping bag, I’m cozy down below freezing. On the other hand, when converted to quilt mode, I can comfortably cowboy camp in the desert or use it for extra comfort around a campfire. However, if you prefer a full mummy bag with a lofty hood or want a more durable product, this may not be best for you. I’ve been a big fan of Therm-a-Rest products for years, and I’m very excited to have this bag for high alpine trips later in the summer and early fall.

Shop the Therm-a-Rest Ohm

The Therm-a-Rest Ohm was donated for purpose of review.