Last updated July 9, 2026
High-Altitude Sleeping Bag Guide: Temperature Ratings by Altitude
The right bag is the difference between resting and shivering at 6,000 m — and the wrong one is genuinely dangerous. Here’s exactly what temperature rating, fill, and features you need at each altitude, and how to choose without overpaying or under-packing.
Match your bag’s rating to your highest camp: roughly +-12°C to -18°C for alpine camps (4,500–5,500 m), -18°C to −-7°C for expedition altitude (5,500–7,000 m), and −-7°C to −4°C or colder above 7,000 m. Use 800–950 fill-power down for warmth-to-weight, a mummy shape with a draft collar and hood, and always pair the bag with a high-R-value insulated pad — the bag alone won’t keep you warm off cold ground.
Temperature rating by altitude
The single most important table on this page — find your zone, read across.
The rating on the tag is where every choice starts — but it’s not the whole story.
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Explore Travel Shop on Expedia →| Zone | Altitude | Rating needed | Fill / type | Weight | Price |
|---|---|---|---|---|---|
| Trek zone | 3,000–4,500 m | +-7°C to +-12°C | Down or synthetic | 2–3 lbs | $150–400 |
| Alpine zone | 4,500–5,500 m | +-12°C to -18°C | Down preferred (weight) | 2–4 lbs | $300–700 |
| Expedition zone | 5,500–7,000 m | -18°C to −-7°C | 900+ fill down | 4–6 lbs | $600–1,200 |
| High altitude | 7,000–8,000 m | −-7°C to −4°C | Expedition-specific down | 5–8 lbs | $800–1,800 |
| Death zone | 8,000 m+ | −4°C or colder | Specialized heavy-duty | 6–10 lbs | $1,500–3,000 |
On this page
How to read the ratings
Three numbers, and only two of them are useful.
Since 2005, quality bags are tested to the EN 13537 / ISO 23537 standard using a heated mannequin, which gives three figures. The comfort rating is the temperature a cold sleeper stays comfortable — the number to plan by if you feel the cold. The lower-limit rating is where a warm sleeper survives eight hours curled up; it’s the number manufacturers usually print on the label. The extreme rating is a survival-only figure — you’ll be cold, possibly dangerously so — and you should ignore it for planning. Note that some premium expedition brands (Feathered Friends, Western Mountaineering) don’t use EN/ISO and rate in-house; their ratings tend to run honest, but they’re not directly comparable to tested numbers.
Down vs synthetic & fill power
For serious altitude, this is a short conversation.
Down (goose, 800–950 fill)
The best warmth-to-weight and packability by a wide margin — decisive when you carry the bag to high camps. Higher fill power means more warmth per gram, so a 900-fill bag is lighter than an 800-fill bag of the same rating. Weakness: it collapses when wet.
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Synthetic
Keeps insulating when damp, dries faster, and costs less — genuinely useful in wet, lower environments. But it’s heavier and bulkier for the same warmth, which is exactly the penalty you don’t want to carry high.
At altitude the case for down is strong: conditions are cold and dry, your tent shelters the bag, and every gram and litre of pack space matters. On 8,000 m peaks the gold standard is a −40°C-rated expedition bag with 850+ fill down.
Features that matter
Beyond the rating, these separate a good expedition bag from a cold night.
- Mummy shape — a snug, tapered cut with far less dead air to heat than a rectangular bag. Non-negotiable for cold.
- Insulated hood & draft collar — a huge share of heat escapes at the neck and head; a cinchable hood and a draft collar around the shoulders seal it in.
- Draft tube behind the zipper — stops a cold stripe of heat loss along the full length of the zip.
- Water-resistant shell — a DWR or hydrophobic-down treatment guards against tent condensation and spindrift.
- Generous cut for layers — at extreme altitude you often sleep in a down suit or with a bottle of hot water; the bag must fit that without compressing its own loft.
It’s a sleep system, not just a bag
The most common — and coldest — mistake is buying only the bag.
Warmth at altitude comes from the whole system: bag, pad, and shelter together.
A sleeping bag doesn’t generate heat — it only traps the heat your body makes. Underneath you, your body weight crushes the down flat, so the bag does almost nothing against the cold ground or snow. That job belongs to your sleeping pad, measured by R-value. For high-altitude camps you want a high R-value — often two pads together, a closed-cell foam beneath an inflatable, which also adds a puncture safety net. A liner adds a few degrees and keeps the bag clean. Every temperature rating on the table above assumes an adequate pad: get the pad wrong and even a −4°C bag will sleep cold.
Frequently asked questions
What temperature rating do I need for a high-altitude sleeping bag?
Match it to your highest camp: +-12°C to -18°C for alpine camps (4,500–5,500 m), -18°C to −-7°C for expedition altitude (5,500–7,000 m), −-7°C to −4°C above 7,000 m, and −4°C or colder in the death zone. Ratings assume a pad and often show the lower limit, not comfort — err warmer.
Down or synthetic for high altitude?
Down, almost always — 800–950 fill gives the best warmth-to-weight and packs smallest, which matters when you carry it high. Synthetic suits wet, lower environments or tight budgets, at a weight and bulk penalty.
What fill power should I look for?
800–950 fill-power goose down for expedition altitude. Higher fill power is warmer per gram, so a 900-fill bag is lighter and more packable than an 800-fill bag of the same rating.
Do I still need a pad with a warm bag?
Yes — it’s not optional. The bag does little underneath you because your weight flattens the down; a high-R-value pad (often two) insulates you from the ground. The bag’s rating assumes it.
Should I buy or rent?
Renting a −40°C bag for a one-off expedition can save hundreds, but condition and hygiene vary and it’s a safety-critical item. If you’ll climb repeatedly, buy quality — a good expedition bag lasts decades with proper storage.
How we built this
Guidance is compiled from the EN 13537 / ISO 23537 rating standards, expedition gear lists for 8,000 m peaks, and manufacturer specifications, cross-checked against our own mountain climbing gear list. Temperature ratings are guidelines based on an average sleeper with an adequate pad — individual warmth varies with metabolism, hydration, fatigue, and conditions, so treat every number as a starting point and build in a margin.
Build the whole kit
Your sleeping bag is one piece of the system — see the complete altitude gear list, layer by layer.
See the full gear list →Was this helpful?
Global Summit Guide is an independent mountaineering resource founded in 2026. The team combines first-hand trekking and climbing experience with in-depth research and professional health and nutrition review to help climbers choose objectives, prepare properly, and stay safe.
Health, altitude, and nutrition content is reviewed by Taylor Ludlow (Registered Nurse) and Brigg Hoopes (Nutritionist).
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