Fill power

Fill power is a measure of the loft or 'fluffiness' of a down product that is loosely related to the insulating value of the down. The higher the fill power, the more air a certain weight of the down can trap, and thus the more insulating ability the down will have. Fill power ranges from about 300 (in³/oz or 175 cm³/g or Lorch 75 mm/30g) for feathers to around 900 (in³/oz or 520 cm³/g or Lorch 225 mm/30g) for the highest quality goose down. The rare and relatively expensive down of certain wild waterfowl species such as the Muscovy duck or Common eider can have higher fill powers than goose down. Higher fill powers are associated with a larger percentage of down clusters and a larger average down cluster size. Fill power is a measure of the loft or 'fluffiness' of a down product that is loosely related to the insulating value of the down. The higher the fill power, the more air a certain weight of the down can trap, and thus the more insulating ability the down will have. Fill power ranges from about 300 (in³/oz or 175 cm³/g or Lorch 75 mm/30g) for feathers to around 900 (in³/oz or 520 cm³/g or Lorch 225 mm/30g) for the highest quality goose down. The rare and relatively expensive down of certain wild waterfowl species such as the Muscovy duck or Common eider can have higher fill powers than goose down. Higher fill powers are associated with a larger percentage of down clusters and a larger average down cluster size. Fill power is the most frequently used measure of down quality. It involves measurements taken of a 20g or one-ounce sample of down in a plexiglas cylinder with a weighted piston compressing the down. The test requires controlled temperature, humidity, and preparation of the sample. All other things being equal, bedding or garments made with high fill power down is lighter and more compressible than an equally warm one made with lower quality down. Fill power can be expressed as cubic inches per ounce (in³/oz). For down sleeping bags a lofting power of 600-650 is considered good quality, 700 - 750 is considered very good, and 800 - 950+ is considered excellent.