For most car campers, a synthetic sleeping bag is the better buy — it's cheaper, still insulates when damp, and is low-maintenance. Choose down if you backpack or count grams: it's warmer for its weight, packs smaller, and lasts longer — but it costs more and must be kept dry. Match the fill to your climate and how you carry it.
Almost every sleeping bag is filled with one of two things: down (duck or goose plumage) or synthetic (polyester fibers). The fill decides warmth-to-weight, packed size, price, and — crucially — what happens when things get wet. It's the first decision to make, before you compare specific models. New to bags? Start with the camping gear checklist, and when you're ready to pick a model, see our best sleeping bag picks.
Down vs synthetic, side by side
The trade-off in one table. “Best for” is the headline; the rest is why.
| Factor | Down | Synthetic |
|---|---|---|
| Warmth for the weight | Best — warmer per ounce | Heavier for the same warmth |
| Packed size | Compresses small | Bulkier packed |
| When it gets wet | Loses loft (unless treated) | Still insulates |
| Drying | Slow | Fast |
| Price | $$$ | $ |
| Lifespan | Longer with care | Loft fades sooner |
| Care | Gentle, special wash | Easy, machine-friendly |
| Best for | Backpacking · cold & dry · counting grams | Car camping · wet · budget |
Down sleeping bags
Down is nature's insulator: tiny plumes trap air for the best warmth-to-weight ratio you can buy, and they compress smaller than anything synthetic. A well-cared-for down bag can last a decade or more. The catch is moisture — untreated down clumps and loses loft when wet — and the price.
- Warmest for the weight (great for backpacking)
- Compresses smallest in your pack
- Longest lifespan with proper care
- Breathable and comfortable across a range of temps
- Most expensive
- Loses insulation when wet (unless treated/DWR down)
- Slow to dry; needs gentle, specific washing
Best for: backpackers, cold and dry conditions, anyone counting grams, and campers buying once for the long haul.
Synthetic sleeping bags
Synthetic fill mimics down with polyester fibers. It's heavier and bulkier for the same warmth, but it keeps insulating when damp, dries fast, costs far less, and shrugs off rough handling and easy machine washing — which is exactly what most car campers actually need.
- Keeps you warm even when damp
- Dries quickly
- Much cheaper
- Easy care; hypoallergenic
- Heavier and bulkier for the same warmth
- Loft (and warmth) fades sooner over years
Best for: car campers, wet or humid climates, budgets, allergies, and anyone who wants a no-fuss bag.
How we compare: these are the consistent, published characteristics of each fill and the patterns across many owner reviews — not lab testing. See how we choose.
So, which should you choose?
Work backwards from two questions: do you carry it, and will it get wet? If you backpack in cold, dry weather and want it to last, pay for down. If you drive to camp, camp in damp places, or just want the most warmth for the money, get synthetic. Either way, the temperature rating and bag shape matter as much as the fill — and a good sleeping pad keeps you warmer than upgrading the bag.
FAQ
Is down or synthetic better for camping?
For most car campers, synthetic — it's cheaper, low-maintenance, and still insulates if it gets damp. Choose down if you backpack or care about weight and packed size: it's warmer per ounce, compresses smaller, and lasts longer, but it costs more and must be kept dry.
Do synthetic sleeping bags keep you warm when wet?
Largely yes — synthetic fill keeps much of its insulating ability when damp and dries fast, which is why it's the safer choice for wet climates, canoe trips, and condensation-prone tents. Untreated down clumps when wet and loses most of its warmth until it dries.
Are down sleeping bags worth it?
If you backpack or camp in cold, dry conditions, yes — down gives the best warmth-to-weight ratio, packs the smallest, and lasts the longest with proper care. For occasional car camping in mild weather, a synthetic bag delivers most of the comfort for a fraction of the price.
What is fill power?
Fill power measures the quality (loft) of down — how many cubic inches one ounce fills. Higher fill power (e.g. 800 vs 600) means more warmth for less weight. It's a quality rating, not a warmth rating; the temperature rating tells you how warm the bag is.
Which is better for backpacking?
Down, in most cases — every ounce and inch of pack space matters, and down wins on both. Use a waterproof stuff sack (and consider water-resistant treated down) to manage the wet-weather risk. Synthetic still makes sense for wet trips or tight budgets.
How do I wash a down sleeping bag?
Use a front-loading machine on gentle with a down-specific wash, rinse twice, and tumble dry low with a couple of clean tennis balls to break up clumps and restore loft. Never dry-clean it. Store it loosely (not compressed) to protect the loft.
