There are several pieces of lingo used when giving the technical information of a well-made down jacket or sleeping bag and one of these that we’re most asked about is Fill Power.

Fill power (FP) is a number measuring the fluffiness and quality of a down product. It correlates properly to the amount of space one ounce of down will occupy in cubic inches. Higher fill power will mean that the down inside your jacket or sleeping bag is better quality, has a higher loft, and will remain firm for longer. This is due to the down clusters being able to hold more air, ensuring better insulation.

Put simply, the higher the fill power, the larger the down feathers and the better the down will be at holding warmth for its weight. Common measurements of FP within our range of products are 650, 750, 800, and 850.

In the image below you can see 3 jars each with the same weight of down, however, you can see that the jars containing higher fill power down are considerable fuller, when equating this to a jacket you can see that you will need considerably less 800 fill power down to fill a jacket, meaning it’ll be considerably lighter and pack down smaller than say a 600 fill power down jacket of the same volume whilst remaining just as warm. If a 600 fill power sleeping bag or jacket had the same fill weight (the amount of down within the jacket) as a jacket or sleeping bag with 800 fill power down, the 800 fill power product would be considerably more insulative.