What does loft mean when it comes to sleeping bags?

What does loft mean when it comes to sleeping bags?

If you’ve been looking at purchasing a sleeping bag and you’ve been stumped by the word ’loft’, don’t worry, you’re not alone! First things first – and you probably know this, but just in case, there are two main types of sleeping bags when it comes to the insulation that keeps you warm: synthetic and down.

What’s a synthetic sleeping bag?

Synthetic sleeping bags use insulation that’s man-made. It tends to be inexpensive and easy to care for but is bulkier and heavier than down. There are many different structures that synthetic fibres can be made into, using all different materials, all of which affect performance – but that’s a topic for another time.


What’s a down sleeping bag?

Down sleeping bags use the insulation that birds use – 'down', which traps the warm air generated by the body. Down is a type of feather that clusters underneath what we typically think of as the feathers on a bird. It’s soft and doesn’t have a stiff quill (which would get uncomfortable in the middle of the night) and is highly regarded for its exceptional warmth-to-weight ratio. This means that down sleeping bags are the go-to for anyone concerned about the size and weight of their sleeping bag.


What is sleeping bag loft?

Ok, so you probably knew all of that, but where does loft come in? Well, it’s specifically used to describe how well down expands when you get the sleeping bag out of its stuff/compression sack and, therefore, how well it traps warm air. The better down is at lofting, the warmer it will keep you, so it’s pretty essential.

Loft is typically measured in terms of ’fill power’ – essentially how much power the down has to fill a space when allowed to loft. More space filled = more warm air trapped = a toasty night’s sleep. Most down falls into the 500-900 fill power range, and is standardly advertised such as 650+, as the manufacturer is indicating the minimum that the down can do at the time of manufacturing.

Loft doesn’t get into how much down is in the sleeping bag (usually measured by weight) or completely determine the quality of the down (how long it will last). It’s only talking about the ability of the down to trap warm air. Therefore, there are still a few other factors to consider when choosing a sleeping bag, but what’s certain is that 500g of 850+ down will be warmer than 500g of 600+ down. This means that if you’re looking at two sleeping bags rated to -5°, the 850+ will have less down, and therefore be smaller and lighter than the 600+ sleeping bag.


This article doesn’t tell you everything you need to know about buying a sleeping bag, but hopefully you’re more confident about knowing what loft and fill power means, and how it impacts your decision. If you’re still unsure or would like to ask other questions about purchasing your next sleeping bag, we encourage you to contact our team so that we can have a chat!

As always, we look forward to hearing your feedback. Feel free to write a comment below! If you would like to receive more personalised advice, contact us on (03) 8840 7014 or at sales@wallarooadventurestore.com.au.

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