8 Best Therm-a-Rest Sleeping Bags to Buy in 2025

The Therm-a-Rest Ohm 20F/-6C is a revelation for backpackers who refuse to compromise between warmth, weight, and versatility. With 900-fill Nikwax Hydrophobic Down, this sleeping bag laughs in the face of moisture—absorbing 90% less water and drying three times faster than untreated down—making it a hero in damp alpine environments. The full-length wrap-around zipper isn’t just a convenience; it transforms the bag into a quilt or allows seamless mating with a partner’s Ohm, turning solo gear into a shared backcountry cocoon. For thru-hikers and minimalist mountaineers, this is ultralight luxury redefined.

In real-world testing across Pacific Northwest forests and Colorado highlands, the Ohm delivered consistent warmth down to its 20°F rating, even in damp bivy tents. Its box-baffled construction with mesh walls eliminated cold spots, while the drawcord collar created a tightly sealed microclimate around the face—critical on windy nights. Packed size is astonishing: it compresses smaller than a 1-liter water bottle, and at just over 2 pounds, it’s a dream for ounce-counters. However, the premium down demands careful handling—extended wet exposure will still degrade performance, and the delicate shell fabric isn’t for abrasive tent floors.

Compared to the Hyperion, the Ohm trades a few degrees of warmth for unmatched adaptability and two-person potential. While the Hyperion is a speed demon for solo fastpacking, the Ohm shines when customization and comfort matter. It’s the ideal choice for alpinists, long-distance hikers, and anyone prioritizing multi-functional design without sacrificing thermal efficiency. For the weight-conscious adventurer who values transformative features and ethical materials, the Ohm outperforms even its lofty price tag.

The Therm-a-Rest Hyperion 32F/0C is a featherweight titan built for adventurers who measure gear in grams and sleep under the stars with relentless efficiency. Weighing a mere 18 ounces, this mummy bag is a masterclass in ultralight engineering—perfect for fast-and-light summer treks or alpine pushes where every ounce counts. Its 900-fill Nikwax Hydrophobic Down resists moisture and maintains loft up to 60 times longer than untreated down, ensuring warmth stays locked in even during unexpected mountain drizzles. For thru-hikers and solo peak-baggers, this is performance distilled to its purest form.

During field tests in the Sierra backcountry and Appalachian Trail shelters, the Hyperion proved its mettle: it provided reliable warmth down to 32°F, especially when paired with a quality pad via SynergyLink Connectors, which eliminate cold gaps and boost thermal efficiency. The ergonomic mummy shape fits snugly without constricting, and the long zipper allows precise airflow control—critical on warm summer nights. Packed size is stellar: it collapses to just 5.5 x 6 inches, slipping easily into even the smallest packs. That said, its minimal insulation makes it unsuitable for true cold-weather use, and the lightweight fabric shows signs of wear with rough handling.

Against the Questar, the Hyperion is significantly lighter and more packable, but sacrifices some comfort and room to move. While the Questar offers better value for casual backpackers, the Hyperion is optimized for speed, weight, and technical conditions. It’s the go-to for alpinists, fastpackers, and anyone who treats their pack like a precision instrument. If ultralight dominance and elite down performance are your priorities, the Hyperion delivers more bang per ounce than any other bag in its class.

The Therm-a-Rest Questar 32F/0C strikes a brilliant balance between performance, comfort, and cost, making it the smart pick for backpackers who want premium features without breaking the bank. With 650-fill Nikwax Hydrophobic Down, it resists moisture and dries faster than standard down—ideal for humid forests or rainy ridge lines. The W.A.R.M. fit (With Additional Room for Multiple positions) is a game-changer, allowing side sleepers and fidgeters to shift freely without crushing insulation or creating cold zones. Paired with SynergyLink Connectors and zoned insulation, it delivers efficient warmth without the ultralight tax.

In real-world use across the Smokies and Cascades, the Questar proved reliable in spring and fall conditions, maintaining comfort down to its 32°F rating when paired with a good pad. At 1.88 pounds, it’s not the lightest, but the added room and durability justify the weight for most weekend warriors. The zoned insulation strategically places down where you need it—torso and feet—while reducing it in less critical zones, optimizing warmth-to-weight. However, its packed size is larger than ultralight rivals, and the 650-fill power means it doesn’t loft quite as high as 800+ fill bags in extreme cold.

Next to the Parsec, the Questar lacks recycled fabrics but offers a more proven track record and slightly better fit for average-sized hikers. Compared to the Hyperion, it’s heavier but far more forgiving in fit and versatility. This is the sweet spot for entry-to-mid-level backpackers who want down performance, ethical materials, and real-world comfort without chasing gram-counting extremes. For those prioritizing value and balanced design, the Questar outshines pricier, more specialized bags in everyday use.

The Therm-a-Rest Parsec 32F/0C is a planet-conscious performer that proves eco-friendly doesn’t mean compromise—this bag delivers ultralight warmth with a conscience. Constructed from GRS-certified 100% recycled fabrics, it slashes environmental impact while maintaining softness, durability, and featherlight performance. At the core is 800-fill PFC-free Nikwax Hydrophobic Down that resists moisture and dries 3x faster than untreated down, making it a trusted ally in wet mountain climates. The heat-mapped zoned insulation is genius: down is concentrated on the torso and feet, trimmed from underused zones, delivering maximum warmth with minimal weight.

Field-tested in Pacific coastal ranges and Rockies alpine zones, the Parsec held steady at 32°F with no cold spots, thanks to its ergonomic baffling and Toe-asis Foot Warmer—a baffled pocket that zips over chilly toes for instant warmth. The SynergyLink Connectors ensure full integration with sleeping pads, eliminating cold bridging. At just over 1.8 pounds and packing down small, it’s ideal for eco-minded backpackers who still demand performance. The anti-snag YKK zipper operates smoothly, though the recycled shell, while durable, isn’t as abrasion-resistant as non-recycled counterparts.

Versus the Questar, the Parsec is lighter, more sustainable, and slightly more technical, but comes at a higher cost. Compared to the Hyperion, it trades a bit of fill power for ethical materials and enhanced comfort features. It’s the top pick for environmentally aware hikers who won’t sacrifice warmth or weight. For those seeking a sustainable yet high-performing down bag, the Parsec offers a cleaner footprint without cutting corners on backcountry reliability.

The Therm-a-Rest Saros 32F/0C is a budget-savvy synthetic sleeper that punches far above its price, offering three-season warmth and thoughtful design without the fragility of down. Its EraLoft synthetic insulation uses hollow fibers to trap heat efficiently, staying warm even when damp—a major advantage in humid or rainy conditions where down fails. The W.A.R.M. fit gives side sleepers and restless campers room to shift without sacrificing thermal efficiency, a rare win in the sub-$200 category. With SynergyLink Connectors and zoned insulation, it integrates seamlessly into a full sleep system, making it more than just a budget backup.

In real-world trials across the Ozarks and Adirondacks, the Saros delivered consistent performance in spring and fall, holding warmth down to 32°F with a good pad. At 2.31 pounds, it’s heavier than down bags, and its packed size (8.5×9.5 inches) takes up more room, but that’s the trade-off for wet-weather resilience and affordability. The synthetic fill doesn’t compress as small or last as long as down, but it’s easier to care for and more forgiving for novice backpackers. It’s not built for extreme cold or gram-counting, but for beginners or fair-weather hikers, it’s a durable, dependable workhorse.

Stacked against the Space Cowboy, the Saros offers a lower temperature rating and better insulation, making it more versatile across seasons. Compared to the Questar, it lacks the lofty feel of down but wins in wet conditions and cost. It’s the ideal entry point for new backpackers, scouts, or car campers who want reliable gear without investment anxiety. For those prioritizing durability, moisture resistance, and value, the Saros is the smart synthetic step into serious backcountry sleep.

The Therm-a-Rest Space Cowboy 45F/7C is the ultimate summer companion—a lightweight, low-maintenance bag built for warm nights, casual campers, and zero-fuss adventures. With EraLoft insulation, it traps heat efficiently using hollow fibers that stay warm even when damp, while drying quickly after morning dew or accidental ground moisture. The GRS-certified 100% recycled nylon shell adds eco-cred without sacrificing softness or durability, making it a sustainable choice for casual outdoor lovers. At just over 2 pounds, it’s easy to carry, and the anti-snag YKK zipper ensures smooth operation night after night.

Tested on lakeside campsites and desert trails, the Space Cowboy excelled in temperatures above 50°F, offering breathable comfort without overheating. The heat-mapped zoned insulation places warmth where it’s needed—torso and feet—while reducing bulk elsewhere, optimizing efficiency. It’s not meant for cold weather, and the lack of advanced fit features makes it less ideal for side sleepers, but for summer backpackers, festival-goers, or roof-top tenters, it’s perfectly tailored. The SynergyLink Connectors are a bonus, allowing pad integration for those stepping up from basic camping.

Next to the Saros 32F, the Space Cowboy is warmer by design but less versatile in cooler conditions. Compared to the Questar, it’s far more affordable and easier to maintain, but lacks the performance ceiling of down. It’s the go-to for recreational campers, youth groups, or warm-weather hikers who want lightweight, eco-friendly, and reliable sleep without complexity. For those prioritizing simplicity, sustainability, and summer readiness, the Space Cowboy outshines pricier, overbuilt alternatives.

The Therm-a-Rest Saros 20F/-6C is a cold-weather synthetic powerhouse, engineered for backpackers who need serious warmth without relying on down. With EraLoft synthetic fill, it maintains insulation performance even in wet, snowy conditions—a critical edge when moisture is inevitable. Rated to 20°F, it’s built for fall hikes, winter basecamps, and shoulder-season expeditions where synthetic reliability trumps ultralight aspirations. The W.A.R.M. fit allows natural movement, a rarity in mummy bags, while SynergyLink Connectors ensure full thermal integration with your pad—eliminating cold spots and maximizing efficiency.

Field-tested in Utah’s high desert and New England snow camps, the Saros delivered consistent warmth down to its rating, especially when paired with a closed-cell pad. At 3.56 pounds, it’s heavy, and its packed size (9.5×10.5 inches) eats into pack space, but that’s the cost of durable, moisture-resistant warmth. The long version fits up to 6’6”, making it ideal for taller users, but the weight makes it less suitable for long-distance hiking. It’s not as lofty as down, and the fabric lacks premium softness, but for wet, cold environments, it’s unbeatable in its class.

Compared to the Ohm 20F, the Saros lacks the ultralight pedigree but wins in wet durability and ease of care. Against the Boost 650, it’s heavier and less comfortable but far more affordable and resilient in extreme conditions. It’s the top choice for winter campers, hunters, or anyone in consistently damp climates. For those prioritizing cold-weather reliability and synthetic resilience, the Saros 20F delivers where down dare not tread.

The Therm-a-Rest Boost 650 20F/-6C redefines sleeping bag comfort with its adjustable design and inclusive sizing, making it the best choice for those who find mummy bags constricting or too narrow. Its patent-pending WarmZip Tech is a game-changer: this centered zipper lets you tighten the bag around your body, reducing internal space and boosting warmth by up to 10 degrees F—perfect for cold nights or petite sleepers. The Regular Wide size (38 inches at shoulder) offers unmatched room for broad shoulders or restless sleepers, a rare find in down bags.

In real-world use across Montana highlands and Appalachian fall hikes, the Boost delivered consistent warmth down to 20°F, especially with the WarmZip cinched. The 650-fill RDS-certified hydrophobic down resists moisture and retains loft, while the multi-use arm holes allow easy access to gear or morning coffee without unzipping. At 3 lbs 5 oz, it’s heavier than ultralight bags, and its packed size (13.5 x 7.5 in) is large, but the trade-off is exceptional comfort and adaptability. The 100% recycled nylon shell with PFAS-free DWR adds eco-cred without sacrificing durability.

Compared to the Ohm 20F, the Boost sacrifices packability for superior fit and warmth customization. Against the Questar, it offers more room and innovative features but at a higher weight and price. It’s ideal for hikers with larger builds, side sleepers, or anyone who values comfort over ounce-counting. For those prioritizing adjustable warmth, roomy fit, and ethical materials, the Boost 650 delivers a sleep experience no traditional mummy can match.