A high fill power of 800 means that this lightweight jacket can provide adequate warmth even though it is not thickly padded with down.
UNDERSTANDING FILL POWER AND FILL WEIGHT
Besides knowing the composition of the padding in a down jacket, there is also a rating that can give you an idea of the level of warmth it provides. You’ll find this indication in a number that is known as fill power, which is likely to be found on the labels attached to the jacket, or in the item description if you’re shopping for it online.
This number typically falls within a range from 400 to 900 – the higher the number, the better the down is in terms of warmth performance.
Fill power indicates the warmth-to-weight ratio – in other words, a jacket with a fill power of, say, 700 will be warmer than another jacket that comes with a 500 rating (a comparison that is accurate only if both jackets actually utilised the exact same amount of down by weight).
As such, while fill power can provide a rough gauge of a jacket’s warmth level, it isn’t necessarily a very precise measure, since down jackets come in a wide variety of designs and will contain differing amounts of padding. It’s possible, too, that a thickly padded jacket with a lower fill power can perform as well as a thinly padded jacket with a higher fill power.
The best way to compare jackets then? Try them out in stores and feel how much warmth each jacket will provide, and whether its weight and bulk are acceptable to you. Also ask the sales staff for help on recommendations that will suit your travel needs.
