Fill power (cuin) and fill weight in down duvets – what matters

In short: Fill power (Cuin) measures how well down loft – the higher, the more warming air with less weight. Values from approx. 600 Cuin are high quality, from 700 premium; Traumwelt is at approx. 750 Cuin. The fill weight (grams) determines the warmth rating and increases with size and season.

What is Cuin (fill power / loft)?

Cuin (cubic inches) indicates the volume that a fixed amount of down takes up. High loft means: The down traps a lot of air and therefore warms strongly – with low weight. That is why a high-quality down duvet feels light and still warms excellently.

What Cuin value is good?

As a guide: from about 600 Cuin you speak of good quality, from 700 premium. Traumwelt down is at approx. 750 Cuin – a premium value for light, durable duvets. (The value can fluctuate slightly due to batches, hence the indication "approx.")

What do 600, 725, 750 or 800 Cuin mean?

So a value like 725 Cuin is in the premium range: The down lofts strongly, the duvet warms well and remains pleasantly light.

800 or 900 Cuin – is the surcharge worth it?

For most sleepers not necessarily. For the same warmth rating, a duvet with higher fill power feels slightly lighter and airier, because it needs fewer grams of filling. It does not automatically become warmer – the warmth is determined mainly by the fill weight. From about 700 Cuin, the difference in everyday life is small, the price difference on the other hand often large.

Good to know: Fill power is measured using different testing methods. The information from different providers is therefore only roughly comparable – a Cuin value without fill weight says little about the duvet.

How many grams of filling does a down duvet need?

There is no single "right" value – the fill weight depends on size and warmth rating. A winter duvet contains significantly more grams than a summer duvet of the same size. Transparency is important: For every Traumwelt duvet, the exact fill weight per size is stated, so you can objectively compare duvets.

Example Traumwelt, each in 135 × 200 cm and with approx. 750 Cuin:

Cuin or grams – which is more important?

Both together. The Cuin value says how good the down is; the gram indication says how warm the specific duvet is. A high loft allows fewer grams for the same warmth – thus a lighter duvet.

Frequently asked questions

Are more grams always better?
Only if you want it warmer. For summer, less filling is better, for winter, a lot.

Why does it say "approx." with the Cuin?
Because natural down is a natural product and the value fluctuates slightly. "Approx. 750" is therefore the honest indication.

How much Cuin should a down duvet have?
From about 600 Cuin you get a high-quality duvet, from 700 Cuin a particularly light premium duvet. Higher values are possible, but bring little in everyday life.

Is a duvet with more Cuin warmer?
Not automatically. For the same fill weight, yes – but providers usually use the higher fill power for a lighter duvet with fewer grams. How warm a duvet is, you see from the fill weight and warmth rating.

Traumwelt transparently states the Cuin and fill weight per size – for a fair comparison.

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