The Fill Power of Down refers to its ability to fill one cubic inch of space. Thus, the higher the Fill Power, the greater the down jacket is at retaining heat and warmth. Fill Power normally ranges from 450 to 900. A down parka jacket with a Fill Power of 550 or higher is considered a good buy, but the higher the Fill Power for a coat, the more a consumer can expect to pay to buy one. Any Down Jacket with a Fill Power of 750 or higher provides great insulation capabilities.\r