What Is Down Fill Power (2026): Fill Weight, Synthetics

The article explains the concept of down fill power, which measures the quality and fluffiness of down insulation. The higher the fill power, the greater the loft and ability to trap heat. Down fill weight, the amount of down in a product, is another important factor to consider when evaluating the warmth of a down-filled item. Together, fill power and fill weight provide a way to compare the relative warmth and performance of different down products.