How to Choose the Right Expedition Sleeping Bag (and Why It Matters More Than You Think)

When you’re deep in the mountains, the right sleeping bag can be the difference between a restorative night’s sleep and shivering until sunrise. Yet it’s one of the most misunderstood pieces of expedition kit — and one of the most common mistakes we see first-time adventurers make.

This guide breaks down exactly how to choose the right sleeping bag for your expedition, whether you’re wild camping in the UK, trekking at altitude in Nepal, or braving sub-zero nights in Patagonia.

Down vs Synthetic: What’s Best for Expeditions?

• Down Sleeping Bags

  • Pros: Lighter, more compressible, and warmer for their weight.

  • Cons: Useless when wet, slower to dry, usually pricier.

  • Best for: Dry, cold expeditions where weight is a priority — think Himalayas, Andes, or winter alpine climbs.

    
    

• Synthetic Sleeping Bags

  • Pros: Retain warmth when damp, cheaper, easier to wash.

  • Cons: Heavier and bulkier for the same warmth rating.

  • Best for: Wet, humid environments — jungle expeditions, UK wild camping, or anywhere moisture is unavoidable.

    
    

Pro tip: If you’re doing a long expedition that involves porters, mules, or vehicle support, bulk doesn’t matter as much — synthetic can be a smart call.

Understanding Temperature Ratings

Manufacturers usually list three numbers:

• Comfort: The temperature at which a standard sleeper will feel comfortable.

• Limit: The lowest temperature at which a standard male sleeper can sleep without waking from cold.

• Extreme: A survival-only rating. Ignore it.

  
  

For example: a bag listed as Comfort -5°C, Limit -10°C, Extreme -25°C is realistically a -5°C bag. Always choose based on the comfort rating, not the marketing hype.

Altitude factor: At 4,000m, a -5°C night can feel far colder thanks to thinner air and fatigue. Err on the warmer side.

Weight vs Warmth: Finding the Balance

• Weekend UK wild camps: 2-season bag (comfort ~0°C) is usually fine.

• Trekking in Nepal (e.g., Annapurna, Everest Base Camp): At least -10°C comfort rating. Nights can hit -15°C even when days are sunny.

• Alpine climbs (Mont Blanc, Matterhorn): Go light but warm — a high-quality down bag around -5°C is perfect if you’re bivvying.

  
  

Patagonia or winter expeditions: You’ll want serious warmth — comfort rating -15°C or better.

Rule of thumb: Cold nights ruin morale faster than heavy packs. Better to carry an extra 300g than to lose sleep.

Features That Actually Matter (And Ones That Don’t)

• Mummy shape: Traps heat better.

• Hood with drawcord: Essential above freezing.

• Zip baffles: Prevents heat loss along the zip.

• Left vs right zip: Personal preference, but left zips are easier if you’re right-handed.

• Stuff sack vs compression sack: Use a waterproof compression sack for expeditions.

• Fancy extras (pockets, glow-in-the-dark zips): Ignore them.

  
  

  

Insider Tips from the Field

1. Always sleep in dry clothes — never climb in with damp socks or base layers.

2. Boost warmth with a liner — silk liners add ~5°C, fleece adds ~10°C.

3. Store it right — never keep your bag compressed when not in use, or it’ll lose loft.

4. Borrow before you buy — if you’re new to expeditions, test a few before investing in a £500 down bag.

   
   

Our Recommended Bags for 2025

• Budget UK Wild Camping: Mountain Equipment Starlight 2 (~£120, synthetic).

• All-Round Trekking: Rab Ascent 700 (~£260, down, -9°C comfort).

• High-Altitude/Cold Expeditions: Mountain Hardwear Phantom -18 (~£600, down).

  
  

Final Thoughts

Your sleeping bag isn’t just another piece of kit — it’s your lifeline when the sun drops. Get it wrong, and you’ll lose sleep, energy, and morale. Get it right, and you’ll wake up ready to face whatever the trail throws at you.

At Crux Expeditions, we put gear to the test in real-world conditions. Check out our expedition kit lists and training weekends to see what we recommend — and try before you buy.