Nemo
Nemo Sonic -18 °C Down Sleeping Bag (Regular)
Best use
- Made for
- Winter mountain
Why these labels
- Winter mountain: The maker states this use, and the published specs do not rule it out.
From the maker's stated use and the published specs.
- Summer wild camp: 6/10 UK, roughly May to September, nights above about 8 °C, sheltered pitches.
- Three-season hills: 7/10 UK hills in spring and autumn. Wind, rain, and nights near freezing.
- Winter camp: 9/10 UK winter or high ground. Below freezing, strong wind, possibly snow.
- Weight: 4/10 How much it adds to your pack, compared with the whole market.
Comfort -10 °C, limit -18 °C (ISO 23537).
Winter camping and cold, frosty UK nights down to about -10 °C comfort
- Comfort
- -10 °C
- Limit
- -18 °C
- Fill
- 800 fill down
- Weight
- 1.47 kg (Regular)
Packed size 9.6 L, 34 cm long and 24 cm across Compare with a 2-litre bottle
About as long as a 2-litre bottle and about two and a half times as wide. Drawn to scale.
Where to buy
Alpinetrek £491.96 In stock. Free delivery. Shop shows list price £599.95. Free UK delivery from £85.
View at shop: AlpinetrekUltralight Outdoor Gear £519.99 In stock. Free delivery. Shop shows RRP £599.99. Free UK delivery over £15.
View at shop: Ultralight Outdoor GearPrices checked 8 Nov 2026 on each shop's own page; shops can change them. We earn no commission on these links; shops are listed by price. More
Our ratings (out of 10)
1 to 10, compared with the whole market. Each says what it's based on. How we score
Warmth
From maker's figures 10/10How cold a night you can sleep comfortably through. 10: The best you can buy for this.
Nemo gives an ISO comfort figure of -10 °C (limit -18 °C) for the Regular, in the -5 °C or colder band. The maker's figure, not re-tested.
Room inside
Estimate: only 2 reviews about room inside (fewer than the 3 we need, so never above 8) 8/10How much room to move, bend your knees and sleep on your side. Roomier is comfier. 8: Clearly better than most.
Both reviewers call the Sonic 0 wide and spacious, with room to sleep in any position and even to store boots inside.
Weight
From maker's figures 4/10How much it adds to your pack. 4: A bit below average.
Nemo's minimum weight of 1.47 kg (without sacks) sits in the 1,300-1,699 g band. SectionHiker weighed its bag at about 1.55 kg, the same band.
Packed size
From maker's figures 4/10How much room it takes in your rucksack. 4: A bit below average.
Nemo states a compressed volume of 9.6 L, in the 9-12.9 L band, so the maker's litres are used. Working the 34 x 24 cm packed size as a cylinder gives about 15.4 L, which would be the 13 L+ band, so treat it as the top edge of its band.
What reviewers say (out of 10)
Ratings marked * are from reviews and are not part of the trip score. They are reviewers' scores, not our own measurements. How we score
Comfort to sleep in*
Reviewers' average 8/10How comfy the shape, hood and fabric feel; not the temperature rating.
3 reviews on comfort to sleep in, e.g. "The fitted sides mean that the hood moves with your face when you turn".
Zip*
Estimate: only 1 review about zip (fewer than the 3 we need, so never above 8) 8/10How smoothly the zip runs without snagging.
1 review on zip, e.g. "it's reinforced here right around the zipper so there's no catching and stuff like that".
In short
Good for
- Winter camping and cold, frosty UK nights down to about -10 °C comfort
- Campers who want one bag for winter and spring: the chest vents let it be used well above freezing
- Side sleepers and restless sleepers who find narrow mummy bags tight
Strengths
- ISO comfort -10 °C and limit -18 °C for a down bag under 1.5 kg
- 800-fill hydrophobic down, with a waterproof breathable footbox and hood to keep tent condensation out of the down
- Wide cut with stretch at the knees: SectionHiker and The Seasons Media both found it roomy for side sleeping
- Thermo Gill chest vents with inside and outside zips, so you can vent heat without getting out; SectionHiker used it up to about 7 °C
- Two draft tubes along the zip and a stiffened zip tape; CaptainBerz felt no cold air through the zip seam
Weaknesses
- Heavy and bulky for its warmth: 1.47 kg and 9.6 L, more than ultralight 800-fill bags of similar rating
- The Regular is only rated to fit 183 cm: CaptainBerz (about 183 cm) found it short, with his feet against the end and slightly chilly
- CaptainBerz thought the Velcro draft collar closure basic, and his own warm-up test gave a middling result
- Only 2 independent sources cover damp performance of the current bag and none has used it long, so damp and durability are estimates, not reviewed scores
Sources
We haven't tested this ourselves. Every score comes from these specs, tests and reviews.
ShowHide sources (5)
- Nemo: Sonic down mummy sleeping bag, Regular specifications
- SectionHiker: NEMO Sonic 0 sleeping bag review (2022 version)
- The Seasons Media: Nemo Sonic down mummy sleeping bag, gear review (800 fill, Long; video, auto-captions read)
- CaptainBerz: NEMO Sonic down sleeping bag, cold-night test (video, auto-captions read)
- OutdoorGearLab: Nemo Sonic 0 review