How to choose your sleeping bag: our guide and 10 models by use
EN ISO 23537 temperature ratings, down or synthetic fill, sleeping bag shape and sleeping pad: key factors for a good night's sleep outdoors, from summer bivouacs to extreme cold.
A poorly chosen sleeping bag means a sleepless night shivering or sweating. The right one depends on three things: the lowest temperature you'll encounter, the weight you're willing to carry, and how you sleep.
This guide gives you the key pointers for reading a technical spec sheet, followed by our selection by use, from lightweight hiking to extreme cold. All the bags shown are available in the Outpost store, with up-to-date prices and stock levels.
Summary
| Product | Ideal for | Price | |
|---|---|---|---|
| Sea to Summit Spark | lightest | from €329.95 | In store |
| Sea to Summit Ascent | most versatile | from €399.95 | Out of stock |
| Sea to Summit Hamelin | synthetic | from €189.95 | In store |
| Sea to Summit Boab | roomiest | from €139.95 | In store |
| Sea to Summit Trek Women's -9 °C | women's bag | from €399.95 | In store |
| Sea to Summit Ember | quilt | from €329.95 | In store |
| Snow Peak Entry Sleeping Bag | budget | €72.00 | Available to order |
| Sea to Summit Alpine -29 °C | expedition bag | from €949.95 | In store |
| Sea to Summit Reactor | liner | from €54.95 | In store |
| Sea to Summit Silk Blend | travel liner | from €89.95 | In store |
For products out of stock at Outpost: retail price observed in France in October 2026.
How the team made its selection
We selected one bag per use: lightweight hiking, versatile three-season, synthetic for damp conditions, roomy fit, women's version, quilt, family camping and extreme cold, plus two liners. The temperatures and weights come from the manufacturers' spec sheets.
Hiking and bivouacking
Bags you can carry on your back
Sea to Summit Spark
For lightweight hiking and touring
The brand's ultralight bag: 850+ cuin goose down treated against moisture, 10 denier nylon shell and a tight mummy fit that limits the air to heat. The 7 °C version weighs 363 g and fits in a water bottle volume, the -18 °C takes you to winter bivouacs. Four temperatures, in Regular, Large or Double.
- 850+ cuin goose down, Ultra-Dry Down
- Limits 7 °C, -1 °C, -9 °C or -18 °C
- 363 g in 7 °C Regular
Sea to Summit Ascent
For a single bag from spring to autumn
Three double-slider zips (full length, half length, feet) allow you to ventilate, get your feet out or open it completely as a quilt. 750+ down treated with Ultra-Dry Down, hood that accommodates a pillow. The -1 °C version weighs 782 g in Regular.
- 750+ cuin goose down
- Free Flow zips on three sides
- -1 °C: 782 g, -9 °C: 1,020 g (Regular)
In the meantime, two alternatives available in store:
Sea to Summit Hamelin
For damp climates and kayak outings
Synthetic insulation keeps its warmth when it gets damp, where down gets squashed. The Hamelin takes advantage of this with a relaxed mummy fit, a full-length zip and a half-zip for ventilation. 100% recycled insulation and fabrics.
- RCS recycled synthetic insulation
- -1 °C: 1,124 g, -9 °C: 1,626 g (Regular)
- 20D Bluesign recycled polyester, PFC-free
Comfort and camping
For sleeping like at home
Sea to Summit Boab
For those who suffocate in a mummy bag
A generous fit and a zip that goes all the way down and opens in both directions: on warm nights, it becomes a quilt. Recycled synthetic insulation, Short, Regular, Long and Regular Wide sizes.
- Mixed roomy fit, opens as a quilt
- -1 °C: women's comfort 2 °C
- Regular 1,391 g
Sea to Summit Trek Women's -9 °C
For chilly sleepers
A feminine semi-rectangular fit and down added where the body cools down fastest, at the feet and the torso. 650+ cuin duck down treated against moisture, Free Flow zips to adjust the warmth. Designed for camping and short outings.
- 650+ cuin duck down
- Feminine semi-rectangular fit
- Regular 1,612 g, compressed 12.8 L
Sea to Summit Ember
For mild nights and side sleepers
A hiking quilt has no back: you lie directly on the mat, which insulates from the ground, and you gain the weight of the down squashed under you. The Ember attaches to the mat with straps, closes at the foot with a cord and opens to ventilate.
- 850+ cuin RDS certified down
- Comfort versions 11 °C or 4 °C
- Regular up to 1.85 m, Long up to 1.98 m
Snow Peak Entry Sleeping Bag
For family camping in summer
A very soft rectangular bag for spring and summer, which can be assembled with a second one to form a double bed. Stored in its cover, it serves as a pillow at camp. The right choice for the car or the van, not for the backpack.
- Spring and summer
- Connectable to a second bag
- Pillow cover, inner pocket
Extreme cold
When the thermometer plunges
Sea to Summit Alpine -29 °C
For winter mountaineering and expeditions
The bag for arctic conditions: 850+ down treated against moisture, double draft collar and anti-cold tube along the zip, and enough room inside to keep slippers, batteries or a water bottle warm. Waterproof and breathable shell against tent condensation.
- Limit -29 °C, 850+ down
- Double draft collar, anti-cold tube
- Regular 1,459 g
Accessories
Gain degrees without changing your bag
Sea to Summit Reactor
To extend a summer bag into mid-season
Slid into the bag, the Reactor adds up to 4 °C in the Lightweight version and up to 8 °C in the Fleeceweight. It also keeps the bag clean: fewer washes, it's down that keeps its loft longer.
- Lightweight: up to +4 °C, 255 g
- Fleeceweight: up to +8 °C, 400 g
- Stretch knit, anti-odor
Sea to Summit Silk Blend
For refuges and hostels
Silk and Thermolite fiber in a 138 g mummy liner: use it on its own when it's warm, in your sleeping bag the rest of the time, or in the questionable sheets of a refuge.
- 28% silk, 72% recycled Thermolite
- Compact 138 g mummy
- Rectangular version with pillow
Understanding sleeping bag temperature ratings
Sleeping bags are tested according to the EN ISO 23537 standard, which provides three values:
- Comfort: the temperature at which a cold person, in a relaxed position, sleeps without feeling cold. This is the reference value for women.
- Limit: the temperature at which a less cold person, curled up, can still sleep for eight hours without waking up from the cold. This is often the value displayed in the sleeping bag's name.
- Extreme: a survival threshold that should never be aimed for. You don't sleep at this temperature; you endure it.
Choose a bag with a comfort rating that matches the coldest expected night, or whose limit rating is at least 5°C lower if you sleep warm.
| Use | Typical nights | Target limit temperature |
|---|---|---|
| Summer, camping, refuge | above 10°C | around 7°C |
| Three seasons, mid-mountain | between 0 and 10°C | around -1°C |
| Late autumn, high mountain in summer | down to -5°C | around -9°C |
| Winter, mountaineering | below -10°C | -18°C and below |
Down or synthetic?
Down offers the best warmth-to-weight ratio and compresses significantly. Its loft is measured in fill power: 650 for good camping down, 850 and above for lightweight hiking. It is sensitive to moisture, hence water-repellent treatments like Sea to Summit's Ultra-Dry Down.
Synthetic is heavier and bulkier, but it retains most of its warmth when wet, dries quickly, and costs less. It is the choice for damp climates, kayaking, and trips where you cannot dry your gear.
The bag isn't everything
The cold comes primarily from the ground. A poorly insulated sleeping pad will ruin any sleeping bag: check its R-value, which measures insulation (above 4 for winter). A sleeping bag liner adds a few degrees, as do a hat and dry socks. And a hot meal before bed helps more than you might think.
To complete your sleeping setup: the Sea to Summit Comfort Plus Insulated sleeping pad and the Aeros Premium pillow, or any of the Inflatable Sleeping Pads.
Frequently asked questions
- How do you store a down sleeping bag?
- Never compress it at home: keep it flat or in a large cotton bag so the down retains its loft. The compression sack is only for hiking.
- Should you wash your sleeping bag?
- As infrequently as possible, using a special down wash and drying it for a long time in the dryer on a low setting with dryer balls. A sleeping bag liner prevents most washes.
- Mummy or rectangular bag?
- The mummy shape heats less air, so it is warmer and lighter. The rectangular shape allows for more movement and can often be opened up like a duvet: ideal for camping, less so in the mountains.
- Can a duvet replace a sleeping bag?
- Yes, from spring to autumn, provided you have a good insulating pad, as a duvet has no back. It is well suited to people who sleep on their side.