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 an ounce of the down can trap, and thus the more insulating ability an ounce of 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 down. Higher fill powers are associated with a larger percentage of down clusters and a larger average down cluster size.