The insulation of a down jacket is tough to beat. But what exactly do the numbers on the sleeves mean and how do you know which down jacket is best for you? Watch our video or keep reading to get the lowdown.
WHAT EXACTLY IS FILL POWER?
Fill power determines the loft or ‘fluffiness’ of down. Higher fill power reflects better quality down that’s capable of trapping more air and providing a better warmth-to-weight ratio. The fill power number on your jacket comes from a standardised lab test and indicates how many cubic inches one ounce of down occupies with a standard weight resting upon it.
As an example, our Epiq Down Jackets are filled with 600 fill power down – which means one ounce of this down takes up 600 cubic inches of space.
COMPARING FILL POWER IN DOWN JACKETS
If Jacket A is filled with 227 grams of 800 fill power, and Jacket B is filled with 227 grams of 700 fill power, Jacket A would be warmer.
If you had 113 grams of 800 fill power in Jacket C, and 227 grams of 600 fill power in Jacket D, they could have similar warmth. However, Jacket C would be lighter and more compressible because it requires less down to get the same result.
HIGHER FILL POWER DOESN’T NECESSARILY MEAN WARMER
A higher fill power number doesn’t automatically mean a jacket will be warmer, as quantity is still an important factor. This image demonstrates that 3 grams of 800 fill power takes up the same amount of space as 5 grams of 550 fill power.
Other factors that affect warmth include whether the jacket has a hood, or how long the jacket is. This highlights why you need to consider how you plan to use the jacket, and whether you need to prioritise warmth, weight, or cost.