Compact CampingDown vs. synthetic insulation
Down is warmer for its weight and packs far smaller; synthetic keeps more of its warmth when damp and costs less. For compact camping, down usually wins — with two clear exceptions.
Warmth for weight: down wins
Down's advantage is loft per gram. Fill power (550, 650, 800, 900) measures how much volume a given weight of down fills — higher numbers trap more air per gram, so an 800-fill bag delivers the same warmth as a 650-fill bag at noticeably less weight and bulk. Synthetic insulation has improved for years but still needs roughly 30–50% more weight for the same warmth.
Packed size: down wins bigger
For a compact kit this is the decisive line: a down bag compresses to half the volume of an equivalent synthetic and springs back happily. If your whole kit must fit a 45-litre pack, the difference between a 3-litre and a 6-litre stuffed bag is a third of your food bag.
Wet performance: synthetic wins
Wet down clumps, loses its loft and insulates barely at all, and it dries slowly in the field. Hydrophobic-treated down resists moisture longer and dries faster, but treatment delays the problem rather than removing it. Synthetic fibres hold their structure when damp and keep a usable share of their warmth. In persistently wet climates — sea kayaking, winter maritime hills, long trips with no drying sun — that resilience is worth real weight.
Price and lifespan
Down costs more up front but, washed and stored properly, keeps its loft for well over a decade. Synthetic fills flatten a little with every compression cycle and typically fade noticeably after a few seasons of regular use. Over ten years the expensive down bag is often the cheaper one.
So which should you buy?
Buy down if packed size and weight matter and you can keep your sleep kit dry — which, with a dry bag and a decent tent, almost everyone can. Buy synthetic if your trips are reliably damp, if the bag will be treated carelessly (kids, lending, festivals), or if the budget simply says so — a good synthetic bag beats a cheap, dishonestly rated down bag every time. Ratings themselves are explained in our temperature ratings guide.
Care in three lines
Store any bag uncompressed — hanging or in a large mesh sack. Air it after every trip; wash rarely and with the correct (down or tech) soap. Never store it damp: mildew ends a bag faster than years of use.