What is Fill Power?

Down (and in fact any insulating material) provides warmth by creating pockets or layers of air that form a barrier against cold from the outside. The thicker the layer of air, the better the insulation will be.

Fill power is a measure of the loft or "fluffiness" of a down product. It is related to the insulating value of the down. The higher the fill power, the more air chambers the down holds and the higher the insulating quality of the down will be. The better the down, the less down is needed to keep you warm.

Measuring the Fill Power

Fill power is measured in CUIN (cubic inch per ounce). To measure this, the down is washed and dried and then put in a Lorch-cylinder. Next, pressure will be put on the down. The height of the down is measured at a certain pressure point. This number indicates the fill power of the down.
Fill power in our duvets can vary from a value of 500 cuin to 900 cuin for the highest quality of down.

The Lorch-cylinder measures fill power

Fill Power Conversion Table

CUIN is the best known quality-indicator for down. Most down products in Europe are currently rated according to the Lorch Fill Power standard recommended by the Swiss-based International Down and Feather Laboratory. UK systems report fill power in cubic inches. Germany and Austria (where our duvets are manufactured) report millimetres per 30 grams.


fill power uk-eu table

Fill Power Down

Which Fill Power is Suitable for You?

How much fill power your duvet needs depends on how light or heavy you like your duvet to feel. If you prefer a very light but warm duvet, we’d recommend a high fill power duvet. If you like your duvet a little heavier, you will want to choose a duvet with lower fill power down. The modern duvet is generally light, so we speak of comparative heaviness.

Preserving Fill Power

It is best to hang out your duvet regularly when the weather is nice and dry, or in a well-aired room. When the down has clumped together you can shake it loose by hand or put it in a dryer with a dampened (and well wrung) towel. The warm moist air in the dryer loosens the tufts of down and creates airiness without losing fill power.

Continue reading, about the differences between a goose down duvet and a duck down duvet.

Down Duvet Buyers Guide

Choose your duvet in 4 simple steps

  1. Duvet size: Which duvet size do I need?
  2. Tog: Choose the right tog
  3. Fill power: What is Fill Power?
  4. Duvet fabric: Good down belongs in a good fabric

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

Do you have any questions? Let us know!
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