What Is Down Fill Power?

Down fill power is a measure of the quality and fluffiness of down insulation. It refers to the ability of down to expand and create air pockets that trap warmth. The higher the fill power, the better the insulation provided by the down.

Fill power is a key indicator of down’s performance because it determines how much loft or volume the down can achieve. Higher fill power down requires less material to provide the same level of insulation, making it lighter and more efficient. In other words, fill power is a measure of the warmth-to-weight ratio of the down, ensuring maximum warmth with minimal weight.

Measuring Fill Power

Fill power is commonly measured in cubic inches per ounce (CUIN). To determine fill power, the down is carefully cleaned and dried before being placed into a specialized device called a Lorch cylinder. Inside the cylinder, a standardized amount of pressure is applied to the down, and its loft or height is measured when this pressure is removed.

Fill power is an important measure of the down’s quality and its ability to provide insulation. Higher fill power values indicate that the down can expand more and create larger air pockets, resulting in better warmth and insulation. Our duvets range from 500 to 850 CUIN, offering products with the highest quality down and excellent insulation properties.

The fill power of our duvets ranges from 500 CUIN to 850 CUIN for products with the highest quality down.

Left: Down drying process. Right: The Lorch cylinder measures down fill power

Down Fill Power Conversion

Fill power is the best quality indicator for down. Most down products in Europe are rated according to the Lorch Fill Power standard recommended by the Swiss-based International Down and Feather Laboratory. UK companies report fill power in cubic inches. In Germany and Austria (where our duvets are manufactured), fill power is measured in millimetres per 30 grams. We made a table to help you navigate the different measurements of fill power:

mm/30g in³/oz CUIN
125 500
150 600
155 618
160 635
170 675
180 725
190 760
200 800
210 820
220 840

How Much Fill Power Do You Need?

To determine the ideal fill power for your duvet, consider your preference for a light or heavy feel. If you desire a very light yet warm duvet, opt for a down duvet with high fill power. However, if you don’t mind a slightly heavier duvet, you can choose one with lower fill power. It’s worth noting that most modern duvets are incredibly lightweight, with minimal differences in weight between various fill powers. Nevertheless, these subtle variations can still hold significance for certain individuals.

Multiple cylinders with different kinds of down and different fill power Multiple cylinders with different kinds of down and different fill power

Maintaining Down

Over time and with use, the fill power of down may naturally decrease. To mitigate this, it’s recommended to regularly air out your duvet by hanging it outside on a dry day or in a well-ventilated room. If the down becomes clumped together, you can gently shake it by hand or place the duvet in a dryer with a dampened (but well-wrung) towel. The warm, moist air will help restore the loft of the down and create air pockets, all while maintaining the fill power. For further guidance on caring for your down duvet and pillows, visit our maintenance page.

If you’re curious to learn more about down, we invite you to explore the distinctions between a goose down duvet and a duck down duvet.

Down Duvet Buying Guide

Choose your perfect down duvet in 4 simple steps.

  1. Duvet Size: Which size do I need?
  2. Tog Rating: Pick the right tog
  3. Fill Power: Understanding fill power
  4. Duvet Fabric: Quality fabric for comfort

Compare all down duvets by price, size, season, brand, fill power, fabric, and down type.

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