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Down Comforter 101: What is Fill Power?

Down Comforter 101: What is Fill Power?
Written By
Photographs By
Laure Joliet for Parachute

Soft, cozy and luxurious, the down comforter is the capstone of the perfect bed setup. Warm but not too hot, snuggly but not too hefty, the right Down Duvet Insert transforms your bed into a cloud of comfort.

Down fill makes the ideal bedding covering because it’s light and lofty yet very breathable. Different than feathers, down is the fluffy coating clustered beneath the feathers of waterfowl that protect them from the elements. Most down can be found on the belly of geese and ducks, as this is the part that is exposed to water and must keep the bird warm.

For hundreds of years, humans have relied on down’s warmth and comfort. Fourteenth-century Europeans layered their mattresses with down-filled featherbeds and pillows, and eventually, we started using down-filled duvets on top, too. Durable and hearty, good down was something that was passed down through generations, and the highest quality down today should perform the same.

The most important thing to consider when buying a Down Duvet Insert is fill power, which is essentially a measurement of how fluffy the down is. The higher the down fill power, the better the blanket. Fill power is expressed as a value, usually in the hundreds, equal to the number of cubic inches one ounce of that particular type of down fills. (For example, one ounce of 600 fill power down will take up 600 square inches of space, while 700 fill power will take up 700 square inches.) It’s a measurement of volume.

Higher fill powers (around 700) means a warmer and lighter blanket. That’s because fluffier down has higher insulating power (it can trap more air), so it requires less down to fill the same space than a lower fill power down (say, 600), which needs to be heavier to get the same amount of warmth. In a nutshell, the best quality duvets have high fill power so they’re perfectly warm yet incredibly lightweight.

You’ll also need to consider your climate and how you like to sleep. Most Down Duvet Inserts – including ours – come in lightweight and all season varieties. The difference here is amount of fill (in ounces). All season duvet inserts have more of the same high fill power down than their lightweight compatriots, making them warm enough for frigid winter nights without being heavy and suffocating.

Finally, you’ll also want to look for a baffle box design, which means the duvet is loosely quilted in a grid pattern to keep the filling evenly distributed throughout the comforter. This allows the down to reach its maximum loft, but keeps it all from sliding to the bottom.

Got all that? Good. Now get the best if you haven’t already: Down Duvet Insert or Down Alternative Duvet Insert.