Down vs synthetic sleeping bag: which is better?

We run though the pros and cons of down and synthetic sleeping bags, to help you pick the right one for your trip

down vs synthetic sleeping bag: two people in sleeping bags in a tent
(Image credit: Steve Halama on Unsplash)

Trying to decide between a down vs synthetic sleeping bag? Our rankings of the best sleeping bags and the best lightweight sleeping bags include both, and both have their pros and cons. In this guide, we'll run through the things you need to know about both types, as well as any extra things to look out for, to help you make your choice.

Down sleeping bags: pros and cons

Down sleeping bags offer lightness and unparalleled warmth, which means you're getting a lot of bang for your buck. However, down also takes a bit of looking after – you need to store it uncompressed, to retain the loft, for example. 

There's another major down-side to down: the opportunity for you to catch hypothermia if they get soaked. Why? Down absorbs the water, clumps together and provides no insulation when wet. Down bags have evolved a wide range of waterproof coatings and down treatments to try and stave off the damp problem, but these are sometimes only partially effective, and the treatments often lose their potency over the years. So you'll need to make sure you keep your down sleeping bag away from condensation and securely covered up if the heavens open.

With down bags, pay attention to the baffle construction, as better sleeping bags employ a range of funky shaping tactics to avoid all the down clumping together at one end, and to prevent cold spots forming between the pockets.

Also keep a sharp eye out for ethical down, down quality (cheaper types will include duck), and fill power. The latter is a measurement of the ‘loft’ you’ll get from 1 gram of down. Better quality down will ‘loft’ (fluff up) better than cheap down, giving you more insulation per gram.

Synthetic sleeping bags: pros and cons

On to the second half of our down vs synthetic sleeping bag face-off. Synthetic bags tend to be heavier for the same warmth rating on a down bag, and are usually bulkier in pack terms, but will see you right in the dampest scenario. Artificial down materials like Thinsulate mean that even the wettest synthetic bag will insulate you.

There are a host of materials that try to strike a balance between weight, durability and warmth, so it’s worth looking at a few. On the other hand, synthetic fill bags suffer from de-lofting over time, which reduces their warmth.

Mark Mayne

Mark Mayne has been covering tech, gadgets and outdoor innovation for longer than he can remember. A keen climber, mountaineer and scuba diver, he is also a dedicated weather enthusiast and flapjack consumption expert.