What is Fill Power?
First published June 2025. Updated June 2026 with a new section on fill power vs fill weight, because the difference matters more than most brands let on.
If you've ever shopped for a doona/duvet and been hit with the term "fill power", you're not alone. It's one of those bedding buzzwords that sounds important (and it is!) but often gets misunderstood. So, let's clear the fluff on what fill power actually means and why it matters.
Fill Power: The Measure of Quality, Not Quantity
Here's the common misconception: people think fill power is about the amount of down stuffed into your doona. It's not.
Fill power is actually a measurement of down quality. Put simply, it tells you how much space 28 grams (one ounce) of down occupies when it's fully fluffed up. The more volume it fills, the better the down.
Imagine a doona filled with tiny, fluffy clouds. That's what high fill power feels like. It's all about the loftiness, which translates to better insulation and a lighter, airier feel.
Fill Power vs Fill Weight: What's the Difference?
This is where most of the confusion lives, so let's settle it once and for all.
- Fill power is quality. How lofty and resilient each individual down cluster is, and how much air it traps.
- Fill weight is quantity. The actual grams of down inside your doona.
They're not the same thing and knowing both is how you buy well. Two doonas can have identical fill power and feel completely different, because one simply holds more down. That's exactly how our range works: every Puff doona is filled with the same premium 800 fill power down, and the only difference between our Warm and Light weights is the fill weight inside. Same quality, different amount, depending on how you sleep. (If you're not sure which is you, our Warm vs Light guide sorts it out in about two minutes.)
The trap to avoid? A doona boasting a generous fill weight of mediocre down. Lots of grams of low fill power down doesn't make a doona luxurious, it makes it heavy. Fill power tells you how good the down is. Fill weight tells you how much warmth you're getting. Quality first, then quantity.
Higher is Better (But Why?)
The higher the fill power, the higher the quality of the down. Here's why:
- Better Insulation: High fill power down traps more air, which means it keeps you warmer without needing to be heavy or bulky.
- Light as a Feather (Literally): With higher-quality down, you get the same (or better) warmth with less weight. Who doesn't love a doona that feels like sleeping under a cloud?
- Longer Lasting: High fill power down is more resilient and maintains its loft over time, so your doona stays fluffy and fabulous for years.
To give you an idea of the scale:
- 400 - 500: Good quality, often used in everyday bedding.
- 600 - 700: Great quality, offering better warmth and loft.
- 800 and above: Premium quality. Incredibly light, lofty, and warm. The pinnacle of down comfort.
As a side note (because we can't resist): Puff's fill power is 800. Translation? That's premium territory. You're welcome.
What Determines Fill Power?
So, what makes one down cluster fluffier than another? It comes down to a few key factors:
- Maturity of the Bird: Older birds (typically geese or ducks) produce larger, more developed down clusters. These mature clusters have longer filaments and a more complex structure, which helps them trap more air, essential for that lofty, cloud-like feeling.
- Species of Bird: Goose down clusters tend to be larger than duck, which is why goose dominates the higher fill powers. It's also what makes 800 fill power duck down genuinely rare. Duck down at this level is the exception, not the rule, and it's the only down we'll put our name on.
- Responsible Sourcing: Down collected and handled under certified standards arrives with its clusters intact, and intact clusters loft better. Ours is RDS certified, traced from farm to finished doona, so the quality (and the ethics) hold up under scrutiny.
- Processing & Cleaning: Clean, intact down clusters perform better. High quality down is gently cleaned to remove dust, oils, and broken pieces without damaging the structure, so the cluster can expand to its full volume when fluffed.
In short: it's not just the bird, it's also the care, the process, and the final integrity of the down itself. All of these work together to determine how lofty (and luxurious) your doona will be.
Why Should You Care?
If you're after a doona that's warm, lightweight and luxurious, fill power should be on your radar. It's a simple yet powerful way to gauge quality and make an informed choice. Plus, knowing the science behind your bedding just feels satisfying, like cracking the code to ultimate comfort.
So next time someone throws around the term fill power, you'll know it's not just fluff. It's physics, craftsmanship and a little bit of magic. At Puff, we don't settle for less than dreamy. We float at 800FP. Read more about Puff doonas.
Sleep light, sleep lofty
Beck ☁️
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