A measurement of the quality of down products. Fill power is determined by placing down in glass tubes and allowing the down to loft for 72 hours. The down is then measured in cubic inches. Down comforters with a higher fill power are lighter, fluffier, and warmer than down comforters with less fill power.
A measure of the density of filling in bedding such as comforters; usually defined as ounce/pound per square inch/foot of goods.
The cubic inches one ounce of down will fill. Top quality fill power ranges from 550 to 700-plus cubic inches.
The measurement of the quality of down. The higher the fill power, the greater the loft and fluff of the down comforter, resulting in light-weight, year-round warmth.
This is key when comparing goods made from down. It's the measurement in which an ounce of down will loft and expand to fill an empty space. Good down comforters usually have a fill power of between 550 and 600 cubic inches. Higher numbers reflect greater warmth.