Fill power is the main way to determine the quality of down. It ranges from about 550 to 900 for high-altitude mountaineering. Fill power is the volume (=loft) in cubic inches that one ounce of the down produces. The higher the fill power, the warmer the down for its weight.
You’ll also see a down-to-feather ratio displayed. This shows the ratio of down to feather. A 90/10 ratio means that the product is 90% down and 10% feather. The higher the down percentage, the warmer the jacket will be.
Down jackets almost always weigh less and compress more than synthetic insulation jackets.
You’ll also see a down-to-feather ratio displayed. This shows the ratio of down to feather. A 90/10 ratio means that the product is 90% down and 10% feather. The higher the down percentage, the warmer the jacket will be.