Best Cold Weather Sleeping Bags for Backpacking: 8 Picks Compared

Our verdict

Our Top Picks

A cold-weather bag for backpacking has two jobs that pull against each other: it has to stay warm on a night below freezing, and it has to ride in a pack for days. We compared eight mummy-style and backpacking-cut bags named for 20°F or colder that Amazon stocks, from bags that weigh under 2 lb in their regular sizes to a 4.5 lb Long, including one with an EN limit of -20°F (EN comfort -4°F). Every weight below names the size it belongs to, and every temperature rating names its type.

That second point matters more than it sounds. Some makers publish EN or ISO test results, which come as a comfort figure and a lower limit figure. Others publish their own rating, tested their own way. A “20°F” on one bag and a “20°F” on another can mean different things, so we never line up ratings of different types against each other. This guide is part of our camp comfort gear section, alongside our other sleep-system guides.

Compare the picks

Compare the 8 Cold Weather Backpacking Sleeping Bags

Every row is the exact size and variant we link. Ratings carry their type: “EN” or “ISO” where the maker publishes a standard test result (comfort / limit), and the maker’s name where the maker publishes its own rating. Compare ratings within one type. Weights and packed sizes are the maker’s figures for the linked size.

How We Chose These Cold-Weather Bags

The bar each bag had to clear

• The bag is named for 20°F or colder. On the EN/ISO bags here the name sits near the EN/ISO limit figure; on the Western Mountaineering bags it is the maker’s own rating. Kelty names the Cosmic Down 0 for 0°F and its spec sheet gives a 5°F temperature rating, its own figure with no standard named.
• It is a bag its maker sells for backpacking (mummy or backpacking cut) that packs into a stuff or compression sack, with a weight the maker publishes for the size we link.
• The maker publishes the bag’s rating, fill, weight and packed size, so each one can be stated with its source.
• Amazon showed the exact size, zip side and rating we link in stock and new when we checked (2026-10-22; the Kelty Cosmic Down 0 on 2026-11-01).
• No two picks are the same model in different sizes. Six of the eight are named for 10°F to 20°F, the shoulder-season-to-early-winter end of cold weather; Kelty’s Cosmic Down 0 is named for 0°F, and one bag has an EN limit of -20°F (EN comfort -4°F).

How to read the ratings here, where the evidence comes from and what cold sleepers say on r/Ultralight

How to read the ratings here

EN 13537 and its successor ISO 23537 test a bag on a heated mannequin and publish two main figures. NEMO’s spec sheet defines them this way: ISO Comfort is the “Temperature at which a cold sleeper remains comfortable,” and ISO Limit is the “Lowest temperature at which a warm sleeper stays comfortable.” Five of the bags here carry such figures: the Parsec and Polar Ranger (labelled EN by Therm-a-Rest), the Disco and Cloud Zip (ISO), and the Trestles (EN-tested, per Marmot).

Western Mountaineering and Kelty publish their own ratings instead. Western Mountaineering’s 10°F and 20°F figures are its own; CleverHiker, which tested the UltraLite, wrote that “Western Mountaineering’s conservative temperature philosophy is another reason we trust the UltraLite in cold conditions.” Kelty’s spec sheet gives the Cosmic Down 0 a temperature rating of 5°F / -15°C and names no test standard for it, so we treat it as Kelty’s own figure. A maker’s own rating is not comparable with an EN or ISO figure, so we do not rank one against the other.

Where the evidence comes from

Specs come from each maker’s product page: Therm-a-Rest’s tech-spec tables, Western Mountaineering’s spec charts, NEMO’s spec comparison, Sierra Designs’, Kelty’s and Marmot’s spec sheets. Where a maker’s figure and its Amazon listing disagree, we give the maker’s figure and say so.

Independent reviews come from CleverHiker (UltraLite 20, Disco 15), Better Trail (Parsec 20F, 2026 version), Halfway Anywhere (VersaLite), Backpackers.com (Trestles 15, Regular) and a field test by Hiking Prince George (Polar Ranger). Four of those five sources do not say which length they tested, and each review’s evidence line says so. We found no independent test of the Sierra Designs Cloud Zip 20, so its review rests on maker specs; for the Kelty Cosmic Down 0 we found none either, and its review adds customer reviews hosted on Kelty’s own page.

What cold sleepers say on r/Ultralight

A May 2026 r/Ultralight thread from a self-described cold sleeper drew advice that applies to any bag here. A reply with 45 upvotes when we read it was about the trail itself: “Another thing to consider: On an actual hike, especially multi day, you will probably sleep even colder than in your garden because your body is in an extreme situation.” Several replies pointed at the pad rather than the bag; one began, “Xtherm. Feels like a heating pad.” (the XTherm is a Therm-a-Rest sleeping pad). Another advised: “Choose a bag that is just big enough so that you don’t have to warm up empty space.” These are owner opinions, not tests, but they are a reason to pick a bag with margin below the lowest temperature you expect.

Detailed Reviews

Therm-a-Rest Parsec 20F/-6C, 900-Fill Roomy Mummy

The Parsec 20F is Therm-a-Rest’s three-season mummy, updated for 2026 with 900-fill hydrophobic duck down and zoned baffles that put more down where Therm-a-Rest wants it. For the Regular we link, Therm-a-Rest lists 1 lb 13 oz, 17 oz of fill, a packed size of 7 x 10.5 in and shoulder, hip and footbox girths of 62, 57 and 46 in. Its ratings are EN comfort 29°F and EN limit 18°F. Features include a Toe-asis foot-warmer pocket in the footbox, a YKK anti-snag zipper, an internal stash pocket and a cinchable hood with draft tubes.

Better Trail reviewed the 2026 Parsec 20F. On fit, its reviewer wrote, “While technically a mummy bag, the Parsec feels roomier than most in the category.” On warmth: “These numbers felt accurate in practice: In sub-freezing conditions, I slept comfortably in base layers without needing to layer up further, which hasn’t always been the case for me with other three-season bags.” The same review places it carefully: “All told, the Parsec strikes a nice middle ground for intrepid backpackers: warmer than a summer-weight 32°F bag, but not quite in the same league as true cold-weather options.” Better Trail does not name the length it tested; its listed 1 lb 13 oz matches the Regular.

Evidence: Independently reviewed, same series. Better Trail, Therm-a-Rest Parsec 20F (2026) review: Parsec 20F (2026), length not stated.

Specs: Therm-a-Rest Parsec 20F/-6C (Regular)

• Rating: EN comfort 29°F, EN limit 18°F (Therm-a-Rest)
• Fill: 900-fill PFAS-free hydrophobic duck down (RDS), 17 oz
• Weight: 1 lb 13 oz (Regular, Therm-a-Rest)
• Packed size: 7 x 10.5 in, compression sack included
• Fits: up to 72 in; girth 62 / 57 / 46 in (shoulder / hip / footbox)
• Shape: mummy with zoned baffles
• Price tier: $$

Western Mountaineering VersaLite, Late-Fall Ultralight Mummy

The VersaLite is a Western Mountaineering mummy with a full down collar, rated 10°F by the maker’s own method. For the 6 ft length we link, Western Mountaineering lists 20 oz of 850+ fill power goose down, a total weight of 2 lb, a stuff size of 8 x 15 in and inside girths of 62, 53 and 39 in. The 10°F is Western Mountaineering’s own rating; the maker publishes no EN or ISO figure for it. The shell is Western Mountaineering’s ExtremeLite fabric, and the full-length zipper has a down-filled draft tube.

Halfway Anywhere reviewed the VersaLite after using it on long trails. Its summary reads: “The Western Mountaineering Versalite is a 32 oz / 907 g, 10°F / -12°C mummy bag with 20 oz / 567 g of 850+ fill down, and it’s the sleeping bag I finally upgraded to.” It continues, “It’s warm down to its rating (I’ve used it down to 15°F / -9°C without extra layers), the zipper never snags, it compresses well, and the warranty has no time limit.” The review dates from 2017, updated in September 2026, and does not name the length; its 32 oz matches the 6 ft weight. The same reviewer noted, “It can be too warm in midsummer, and it’s expensive.”

Amazon’s buy box for this listing rotates between outdoor retailers; at our last check (2026-11-01) it was Backcountry, and earlier Ascent Outdoors.

Evidence: Independently reviewed, same series. Halfway Anywhere, Western Mountaineering VersaLite review: VersaLite 10°F, length not stated.

Specs: Western Mountaineering VersaLite (6 ft, right zip)

• Rating: 10°F (Western Mountaineering’s own rating; no EN/ISO figure published)
• Fill: 850+ fill power goose down, 20 oz (6 ft)
• Weight: 2 lb (6 ft, Western Mountaineering)
• Packed size: 8 x 15 in stuff size
• Fits: 6 ft length; inside girth 62 / 53 / 39 in (shoulder / hip / foot)
• Shape: mummy with full down collar; loft 6.5 in (maker)
• Price tier: $$$

NEMO Disco Endless Promise 15, Side-Sleeper Spoon Bag

The Disco uses NEMO’s Classic Spoon shape, cut wider at the elbows and knees so side sleepers can draw their knees up. For the Men’s 15°F Regular we link, NEMO lists ISO comfort 27°F and ISO limit 16°F, 1 lb 7 oz of 650 FP hydrophobic down, a minimum weight of 2 lb 11 oz, a packed weight of 2 lb 14 oz and a packed size of 11.5 x 8.5 in. It has integrated Thermo Gill vents, a Blanket Fold draft collar, a waterproof hood and footbox, and it comes with a compression sack. The Endless Promise label means NEMO takes it back for recycling at the end of its life. NEMO lists its best use as “Backpacking, Car Camping.”

CleverHiker reviewed the Disco 15 Endless Promise, men’s and women’s versions, without naming the size. Its reviewers wrote, “We think of the Disco as a crossover bag: heavier than our ultralight picks, but unusually comfortable and versatile for people who split time between backpacking and car camping.” CleverHiker lists a 25°F comfort rating for it; NEMO’s own ISO comfort figure is 27°F, and we use NEMO’s.

Evidence: Independently reviewed, same series. CleverHiker, best backpacking sleeping bags: Disco 15 Endless Promise, men’s and women’s; size not stated.

Specs: NEMO Disco Endless Promise (Men’s 15°F, Regular)

• Rating: ISO comfort 27°F, ISO limit 16°F (NEMO)
• Fill: 650 FP hydrophobic, PFAS-free, RDS-certified down, 1 lb 7 oz
• Weight: 2 lb 11 oz minimum, 2 lb 14 oz packed (Regular, NEMO)
• Packed size: 11.5 x 8.5 in, compressed volume 8.8 L
• Fits: up to 6 ft
• Shape: Classic Spoon (wider at elbows and knees)
• Price tier: $$

Western Mountaineering UltraLite, Trim Ultralight Mummy

The UltraLite, rated 20°F by Western Mountaineering’s own method, is the sibling of the VersaLite in Western Mountaineering’s ExtremeLite series. For the 6 ft length, the maker lists 16 oz of 850+ fill power goose down, a total weight of 1 lb 13 oz, a 7 x 13 in stuff size and inside girths of 59, 51 and 38 in. The 20°F is Western Mountaineering’s own rating. It has a full-length #5 YKK zipper, a down-filled draft tube and a fully insulated draft collar. We link the 6 ft left-zip version; Western Mountaineering’s spec chart gives the same figures for either zip side. It is sold by Backcountry, a third-party seller, on Amazon at the time of writing, at or below Western Mountaineering’s list price for this size.

CleverHiker tested the UltraLite 20 and wrote, “Our experience includes an Arizona Trail thru-hike and cold nights in Colorado and Utah, including desert conditions in the teens with an appropriate pad and layers.” It also wrote, “Western Mountaineering’s conservative temperature philosophy is another reason we trust the UltraLite in cold conditions.” CleverHiker does not name the length it tested. It lists a 25°F comfort rating without naming a standard; Western Mountaineering publishes none, so we do not use that figure.

The UltraLite and the VersaLite are the same series. The UltraLite is the lighter, trimmer bag, with Western Mountaineering’s own 20°F rating; the VersaLite adds 4 oz of down and Western Mountaineering’s own 10°F rating for 3 oz more weight in the 6 ft size.

Evidence: Independently reviewed, same series. CleverHiker, best backpacking sleeping bags: UltraLite 20, length not stated.

Specs: Western Mountaineering UltraLite (6 ft, left zip)

• Rating: 20°F (Western Mountaineering’s own rating; no EN/ISO figure published)
• Fill: 850+ fill power goose down, 16 oz (6 ft)
• Weight: 1 lb 13 oz (6 ft, Western Mountaineering)
• Packed size: 7 x 13 in stuff size
• Fits: 6 ft length; inside girth 59 / 51 / 38 in (shoulder / hip / foot)
• Shape: mummy with full collar; loft 5.5 in (maker; Amazon’s listing says 5 in)
• Price tier: $$$

Sierra Designs Cloud Zip 20, 800-Fill DriDown Mummy

The Cloud Zip is the zippered version of Sierra Designs’ Cloud bag, a “Classic lightweight mummy shape” filled with 800-fill DriDown, Sierra Designs’ water-resistant treated down. For the Regular we link, Sierra Designs lists ISO comfort 28°F and ISO limit 17°F, 14.74 oz of fill, a weight of 1.94 lb and a packed size of 7.5 x 7.5 x 16 in. The Amazon listing’s spec line gives the trail weight as 1 lb 15.1 oz, which matches. Features include a self-sealing foot vent, an anti-snag zipper, a draft collar and a stuff sack plus storage bag.

We found no independent test of this 2026 model, so everything here is Sierra Designs’ own data. The seller on Amazon is Camp Club, a third-party store, with Amazon handling shipping.

Evidence: No independent test; maker specs. Source: Sierra Designs product page (maker).

Specs: Sierra Designs Cloud Zip 20 (Zip, Regular)

• Rating: ISO comfort 28°F, ISO limit 17°F (Sierra Designs)
• Fill: 800-fill DriDown, 14.74 oz
• Weight: 1.94 lb (Regular, Sierra Designs; the listing says 1 lb 15.1 oz trail weight)
• Packed size: 7.5 x 7.5 x 16 in
• Fits: up to 6 ft; girth 62 / 58 / 40 in (shoulder / hip / foot)
• Shape: mummy, full-length zipper, self-sealing foot vent
• Price tier: $

Kelty Cosmic Down 0, 550-Fill Down 0°F Bag, Long Size

The Cosmic Down 0 is the colder sibling of Kelty’s Cosmic Down 20, with the same 550-fill down, trapezoidal baffles, full draft tube, draft collar, stash pocket and expanded footbox. We link the Long, which Kelty says fits sleepers to 6 ft 6 in: Kelty lists a weight of 4.5 lb, 41.6 oz of fill, a 10 x 18 in stuff sack and an 84 in length. Kelty’s spec sheet gives a temperature rating of 5°F / -15°C, despite the 0 in the name, and names no test standard for it, so we do not set it against the EN or ISO figures of other picks. Kelty’s spec sheet lists the shape as semi-rectangular; we could not read a shoulder or hip girth for the Long.

We found no independent test of the current Cosmic Down 0. Kelty’s own product page hosts customer reviews, which are owner reports, not tests, and do not name the size. One reviewer wrote, “We went snow camping recently and this bag was cozy and toasty and just really awesome.” Another, 6 ft 3 in, wrote that “the bag fits perfect” and added a caveat: “the actual stuff sack with the sleeping bag is quite bulky. There are no utility straps on the stuff sack making it hard for me to attach it to my pack.”

We link the Long (Kelty part number 35413524LR, which matches the Amazon listing); Kelty showed the Regular as unavailable when we checked. It is sold by Camp Club, a third-party seller, on Amazon at the time of writing, and was priced at Kelty’s own list price for the Long when we checked.

Evidence: Owner reports only (maker-hosted customer reviews). Kelty, Cosmic Down 0 product page: size not stated; no independent test found.

Specs: Kelty Cosmic Down 0 (Long)

• Rating: 5°F / -15°C (Kelty’s own temperature rating; no standard named)
• Fill: 550-fill down, 41.6 oz (Long)
• Weight: 4.5 lb (Long, Kelty)
• Packed size: 10 x 18 in stuff sack
• Fits: up to 6 ft 6 in; 84 in length
• Shape: semi-rectangular per Kelty’s spec sheet
• Price tier: $$

Marmot Trestles 15, Synthetic-Fill Mummy

The Trestles 15 is Marmot’s synthetic mummy, insulated with Spirafil. Marmot lists it as EN-tested, with a tested comfort of 27.3°F and a tested limit of 16.0°F, and gives the Regular a weight of 3 lb 6.1 oz, a compressed volume of 12.6 L and an 18.9 x 9.4 in stuff sack. It has a 3D footbox, a fold-down secondary zipper and a two-way locking main zipper. Amazon.com sells it.

Backpackers.com reviewed the Regular; its review names “the Men’s Marmot Trestles 15 in a Regular size, which fits people up to roughly 6 feet in length.” Its reviewer wrote, “The Marmot Trestles 15 is a classic synthetic fill mummy bag which nods to Marmot’s history of creating industry-leading sleeping bags.” On a snow-camping night near 24°F without a foam pad under his air pad, he was chilled but made it through by adding his down jacket. He also wrote, “The Trestles 15 does not, however, have a draft collar to seal out cold air, which I consider a must on any bag rated below freezing.” On weight, his spec table reads, “Lightweight for a camping sleeping bag, slightly heavy for a synthetic backpacking bag rated to this temperature.”

The same review has reservations about warmth and build, side by side with the EN figures. Next to them it says: “This bag is rated quite warm, but our tests show that it doesn’t feel as warm as it tests.” On the limit figure: “This means it is survivable at 16 degrees, but not really built for that kind of cold.” The reviewer also wrote, “Overall I tested the Trestles 15 down to its cold-wire, and while it’s not outstanding, it did better than expected.” On fit: “Personally, I enjoy the roomy cut of the Trestles 15 for car camping and couch surfing, but I would likely choose a slimmer cut for backpacking in temperatures near the bag’s lower limit.” On durability: “The bag is still in good shape, though some of the exposed stitching has come loose or popped in places.” and “My major issue with the Trestles 15 is some anxiety around durability.” Backpackers.com calls it a hybrid bag, did not make it one of its picks, and wrote instead: “For backpacker-specific folk, we highly recommend starting with the Kelty Cosmic Down 20, because while it’s more expensive, you get a much more compressible, lightweight, and warm sleeping bag that will last longer.”

Evidence: Independently reviewed, exact model. Backpackers.com, Marmot Trestles 15 review: Trestles 15, Regular.

Specs: Marmot Trestles 15 (Men’s Regular, left zip)

• Rating: EN comfort 27.3°F, EN limit 16.0°F (Marmot, “EN-tested”)
• Fill: Spirafil synthetic insulation (fill power not applicable)
• Weight: 3 lb 6.1 oz (Regular, Marmot)
• Packed size: 18.9 x 9.4 in stuff sack; 12.6 L compressed
• Fits: Regular, 72 in (Backpackers.com); shoulder girth 62 in
• Shape: mummy with 3D footbox and fold-down secondary zipper
• Price tier: $

Therm-a-Rest Polar Ranger -20F/-30C, Deep-Cold Winter Bag

The Polar Ranger is Therm-a-Rest’s winter bag, which the maker says was designed with polar explorer Eric Larsen. For the Regular we link, Therm-a-Rest lists EN comfort -4°F and EN limit -20°F, 34 oz of 800-fill hydrophobic duck down, a weight of 3 lb 4 oz and a packed size of 8.5 x 10 in. Side vents zip open so you can use your arms outside the bag, a stiff snorkel hood with a magnetic closure vents exhaled moisture, and the footbox has the Toe-asis pocket.

Hiking Prince George tested an earlier version of the Polar Ranger in northern British Columbia in February 2024, inside a bivy on two insulated pads: “The temperature was recorded outside using my Thermometer at -22C (-8F) but temps fluctuated between -20C to -30C after 2 hours lying inside the sleeping bag wearing a minimal base layer, temp inside the sleeping bag was recorded at +22C.” That test does not name the length, and it is of an earlier version: the 2026 bag we link has a revised snorkel hood and fit, per Therm-a-Rest.

One note on the listing: Amazon’s page title for this ASIN ends in “Long”, but Amazon’s variant selector and product data mark it as the Regular (Standard). Check the size shown before you order.

Evidence: Independently reviewed, previous generation. Hiking Prince George, cold temperature sleep system test: Polar Ranger, earlier version (Feb 2024), length not stated.

Specs: Therm-a-Rest Polar Ranger -20F/-30C (Regular)

• Rating: EN comfort -4°F, EN limit -20°F (Therm-a-Rest)
• Fill: 800-fill PFAS-free hydrophobic duck down (RDS), 34 oz
• Weight: 3 lb 4 oz (Regular, Therm-a-Rest)
• Packed size: 8.5 x 10 in
• Fits: up to 72 in; girth 64 / 59 / 46 in (shoulder / hip / footbox)
• Shape: mummy with side arm vents and snorkel hood
• Price tier: $$$

Buying Guide: Choosing a Cold Weather Backpacking Sleeping Bag

Comfort, limit and the number on the bag

The name on a bag (“15”, “20F”) is usually close to one of its ratings, but which one varies. On the EN/ISO bags here, the name sits near the limit figure: the Disco 15 has an ISO limit of 16°F and the Parsec 20F an EN limit of 18°F, while their comfort figures are 27°F and 29°F. The comfort figure is the one the standard ties to a cold sleeper; the limit figure is for a warm sleeper curled up. If you sleep cold, plan around comfort. Western Mountaineering and Kelty publish their own ratings, so read those on their own terms. Picks with EN or ISO figures: Parsec 20F, Disco 15, Cloud Zip 20, Trestles 15, Polar Ranger.

Weight and packed size

Weight depends on size, so compare the size you need. In their regular or 6 ft sizes, the UltraLite and the Parsec are listed at 1 lb 13 oz and the Cloud Zip at 1.94 lb; the VersaLite is 2 lb, the Disco 2 lb 11 oz minimum, the Polar Ranger 3 lb 4 oz and the Trestles 3 lb 6.1 oz. The Kelty Cosmic Down 0 we link is a Long, which Kelty lists at 4.5 lb: the heaviest bag in this guide as linked, more than a pound over the Trestles 15 in Regular, so it is not in that list. Packed sizes run from the Parsec’s 7 x 10.5 in to the Trestles’ 18.9 x 9.4 in stuff sack. Picks: Western Mountaineering UltraLite, Therm-a-Rest Parsec 20F, Sierra Designs Cloud Zip 20.

Down or synthetic

Seven of the eight bags use down, from Kelty’s 550-fill to Therm-a-Rest’s 900-fill; higher fill power means less weight and bulk for the same warmth. Several makers treat their down to resist moisture: Therm-a-Rest and NEMO call theirs hydrophobic, and Sierra Designs uses DriDown. Marmot’s Trestles uses Spirafil synthetic fill, which costs weight and bulk. Picks: Marmot Trestles 15, Kelty Cosmic Down 0.

The pad, shelter and clothes around the bag

An EN/ISO rating assumes an insulated pad under you; the r/Ultralight advice above points the same way. Our sleeping pad guide lists each pad’s ASTM R-value. For the shelter, see our guides to tents for winter and two-person backpacking tents, and how to insulate a tent for winter. Sleeping in dry layers helps too; our cold weather hiking pants guide covers the trail side.

Frequently Asked Questions

Pick a bag whose comfort figure (for EN/ISO bags) sits at or below the lowest temperature you expect, with some margin if you sleep cold. On EN/ISO bags the limit figure is lower than the comfort figure: the Parsec 20F’s are 29°F comfort and 18°F limit. For a maker’s own rating, such as Western Mountaineering’s or Kelty’s, use the maker’s guidance.

For nights around freezing and a little below, often yes; for winter nights in the single digits or colder, a 20°F bag is short. Better Trail described the Parsec 20F as “warmer than a summer-weight 32°F bag, but not quite in the same league as true cold-weather options.” If you expect nights well below freezing, look at bags with lower figures on the same scale you use: among the EN/ISO bags here, the Polar Ranger has EN comfort -4°F and EN limit -20°F. The VersaLite carries Western Mountaineering’s own 10°F rating, which is not on the EN scale.

As far as its rating and your setup allow. Among the bags here, the Polar Ranger has an EN limit of -20°F and an EN comfort of -4°F; for trips where nights sit near 0°F, see our 0-degree sleeping bag picks. Kelty rates the Cosmic Down 0 at 5°F by its own figure, with no standard named. Under EN/ISO, the extreme figure some makers publish is a survival threshold, not a temperature to plan a night around.

Down packs smaller and weighs less for the warmth; synthetic fill keeps some insulation when damp but weighs more. The Trestles 15 is the synthetic bag here at 3 lb 6.1 oz in Regular. Therm-a-Rest, NEMO and Sierra Designs use water-resistant treated down as a middle path.

In the regular or 6 ft sizes we link, the bags here are listed from 1 lb 13 oz (Parsec 20F and UltraLite) to 3 lb 6.1 oz (Trestles 15). The Polar Ranger (EN limit -20°F, EN comfort -4°F) is listed at 3 lb 4 oz in Regular. The Kelty Cosmic Down 0 we link is a Long at 4.5 lb, per Kelty, the heaviest bag here as linked.

The bottom line

Final Verdict

For a roomy, light bag with EN comfort 29°F and EN limit 18°F, the Therm-a-Rest Parsec 20F/-6C (check price) is our starting point at 1 lb 13 oz in Regular. For nights in the teens, the Western Mountaineering VersaLite (check price), which Western Mountaineering rates at 10°F by its own method, weighs 2 lb in the 6 ft size. For side sleepers, the NEMO Disco Endless Promise 15 (check price) gives room at the knees and elbows with ISO figures of 27°F comfort and 16°F limit. The Western Mountaineering UltraLite, Sierra Designs Cloud Zip 20, Kelty Cosmic Down 0, Marmot Trestles 15 and Therm-a-Rest Polar Ranger cover a trim mummy with Western Mountaineering’s own 20°F rating, an ISO-rated budget mummy, a long 550-fill down bag with Kelty’s own 5°F rating, synthetic fill and deep cold, and each review names its sources.

Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.