Fill Power is a term you've probably come across when looking at down textiles. Down fill products are made of down clusters, a three-dimensional cluster with fine filaments extending in all directions. Fill power denotes the size of down clusters in a fill. Larger clusters of down represent higher fill power. Fill power can also be understood as the measurement of space a single ounce of down occupies. It is the best quality indicator for down, so you can typically find fill power listed on most premium 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 formulas below will help us better understand the relationship between fill power and the weight of down fill:

• Warmth level of an 800 fill power comforter with filling weight 40 oz = Warmth level of a 400 fill power comforter with filling weight 80 oz
• Warmth level of an 800 fill power comforter with filling weight 40 oz > Warmth level of a 400 fill power comforter with filling weight 40 oz

Five Facts on Fill Power

For a given weight of down:

• The higher the fill power the higher quality your comforter/pillow will have;
• The higher the fill power the higher your comforter/pillow will loft;
• The higher the fill power, the better it will retain its loft and firmness;
• The higher the fill power the more air your comforter/pillow traps;
• The higher the fill power the better the insulating power will be;

Down Fill Power and Synthetic Fills

Synthetic fills are designed to replicate the qualities of down, and retain them even in wet weather and humid conditions. 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.

Final Thoughts

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!