What is fill power? A simple guide to down bedding

Fill power is the number that tells you how fluffy and lofty the down in your duvet or pillow is. A higher fill power means lighter, airier bedding that keeps you warm without the weight. It's one of the most useful numbers on a bedding label, and once you know what it means, comparing duvets and pillows gets a lot easier.

What is fill power?

Fill power measures how much space a set amount of down or feather fills when it's allowed to puff up. It's usually written as a number followed by FP, for example 650FP. The test works by weighing out one ounce of filling and measuring how many cubic inches it takes up. The more space it fills, the higher the number.

Bigger, more mature down clusters trap more air, so they fill more space. More trapped air means more warmth for the same weight. That's why a high fill power duvet can feel light as anything and still keep you cosy.

Fill power vs tog: what's the difference?

These two numbers often get mixed up, but they tell you different things.

• Tog tells you how warm the finished duvet is.
• Fill power tells you about the quality of the filling inside it.

Two duvets can share the same tog and have very different fill powers. The one with the higher fill power reaches that warmth with less filling, so it feels lighter and drapes more softly over you. The lower fill power duvet needs more filling to get to the same tog, so it feels heavier. Neither is wrong. It just depends on what you like.

If you're still working out how warm you want your duvet to be, our guide to duvet tog ratings covers that side of things.

Fill power across our range

To give you a feel for the numbers, here's how fill power changes across some of the duvets we sell. As the share of down goes up, so does the fill power.

Always check the product page for the exact details of the item you're looking at, as fill power can vary between products.

What fill power should you choose?

Under 400FP: great value and supportive

Feather-rich bedding sits at this end. It feels weightier and more supportive, which plenty of people love, especially in pillows. A duck feather and down duvet (85:15) is a comfy, budget-friendly way to get natural filling on your bed.

Around 400FP to 650FP: the happy middle

More down in the mix makes bedding lighter and softer. This range suits people who want a bit more fluff without going all the way to pure down.

650FP and above: light and lofty

This is where pure down and down-rich bedding lives. It's light, cloud-soft and very good at holding in warmth. A 100% Hungarian goose down duvet at 750FP is a lovely treat if you want warmth without weight.

Duck down or goose down?

Goose down clusters tend to be larger than duck down clusters, which is why goose down often reaches a higher fill power. That said, good duck down can match goose for loft, as you can see with our 100% European duck down duvet. Duck down usually comes in at a friendlier price, so it's well worth a look if you want pure down on a budget.

Does fill power matter for pillows?

It does, but in a slightly different way. In a pillow, a higher fill power gives a softer, springier feel. A lower fill power, feather-rich pillow gives firmer support. Side sleepers who need a firm pillow can do very well with a feather-rich blend, while front sleepers often prefer the softness of a down-rich pillow. Have a browse of our pillows to see the different blends side by side.

Looking after high fill power bedding

A little care keeps down bedding lofty for longer:

• Give your duvet and pillows a good shake each morning to spread the filling out.
• Air them out now and then on a dry day to keep them fresh.
• Use a duvet cover and pillowcase to keep them clean.
• Always follow the care label before washing.

Fill power FAQs

Is a higher fill power always better?

Not always. Higher fill power means lighter, fluffier bedding. If you prefer a weightier duvet or a firmer pillow, a lower fill power feather blend might suit you better.

Does fill power affect warmth?

Indirectly. A higher fill power filling traps more air, so it needs less filling to reach a given warmth. The tog rating is what tells you how warm the finished duvet is.

Why do some duvets not show a fill power?

Fill power is mainly used for feather and down bedding. Synthetic fillings are measured differently, so you won't usually see a fill power on them.

Can I get a high fill power duvet in a summer tog?

Yes. Our down duvets come in 4.5, 9, 10.5 and 13.5 tog, so you can pair a high fill power with whatever warmth suits you.

Ready to feel the difference? Browse our duvets and the rest of our bedding, with free delivery to England, Wales and most of Scotland.