Fill Power is a term you’ve probably heard a bunch when looking at down textiles, but what is “fill power”? Fill power is the measurement we use for the amount of space one ounce of down takes up. It is the best quality indicator for down, so you can typically find fill power listed on the more premium of comforters. It’s important to know that down fill power doesn’t tell us how warm a comforter will be because there are too many other factors involved affecting warmth, including how much down fill is in the comforter. These few formulas below will help us better understand the relationship between fill power and the weight of down fill:
For a given weight of down:
Some of you may already know that down creates amazing warmth but doesn’t do too well in wet and humid conditions. Synthetic fills are designed to replicate the qualities of down, but retain them even when wet. Synthetic fills have no equivalent test to down fill power, and different synthetic fills have different characteristics, so it’s tricky to accurately measure any synthetic insulation efficiency using down fill power.
Although fill power is an important factor to think about when purchasing your own down comforter, you also might like to take into consideration the size, weight, thread count, construction, design, and so on. All these can have a surprisingly large impact on your mission to have a great night’s sleep!