The Edit — Bedding
Down or Down Alternative: Fill Power Explained
Fill power is the only number on a duvet label that means anything precise, and it does not measure warmth. It measures how much loft an ounce of down produces, which is a different claim entirely.
This guide is research-led: we have not handled these units ourselves. If you buy through our links we may earn a commission — it never changes a pick. How we choose
Two duvets can both say 700 fill power and one can be half as warm as the other. The number describes the quality of the down, not how much of it is in the duvet, and the second figure is the one that usually goes unprinted.
Fill power measures loft, not warmth
Fill power is the volume in cubic inches that 1 ounce of down occupies after it has been conditioned and allowed to loft. A 700 fill-power down expands to 700 cubic inches per ounce; a 550 expands to 550.
Loft is what traps air, and trapped air is what insulates, so higher fill power means more insulation per unit of weight. It does not mean more insulation. Testing is done to a published laboratory method — the International Down and Feather Laboratory is the reference most brands cite — and a rating with no lab behind it is a marketing figure.
The usable bands:
| Fill power | What it indicates |
|---|---|
| 400–500 | Immature or heavily blended down. Heavy for its warmth. |
| 550–650 | The mainstream band. Good value, more weight for the same warmth. |
| 700–800 | High-grade cluster. Noticeably lighter for equal warmth. |
| 850+ | Specialist. Expensive, and the gain over 800 is small. |
Warmth is fill power multiplied by fill weight
Fill weight is how many ounces of down went in, and it is the number that decides how warm the duvet is. Fill power decides how much that warmth weighs on you.
A 600 fill-power duvet with a generous fill weight outperforms an 800 fill-power duvet with a thin one, every time. Where fill weight is absent from the listing, the fill power on its own is unanswerable — which is why it is so often the only figure shown.
At marketplace prices neither figure usually appears, and the reason is that the fill is not graded down at all.
Goose Down Fiber and Waterfowl Feather Comforter, Queen
A feather-and-fibre blend rather than graded down, which is what almost everything sold as a down comforter at this price actually is.
Current price shown on Amazon. We may earn a commission.
| Fill | Feather and down fibre |
|---|---|
| Fill power | Not stated |
| Watch | Feather escape reports split |
Owners consistently call it soft, warm and better-looking than the price suggests. What it is not is a fill-power purchase. The listing states none, because feather-and-fibre blends are not rated on that scale and the down content is a minority of the fill.
The divided reports on feather escape are that specification talking. Quills work through ticking that is not down-proof, and a shell tight enough to hold a feather is a tighter weave than this price usually buys. Use a cover, and expect the occasional quill.
Buy it if
- You want the feel of natural fill at a synthetic price
- You will use a cover
Don't buy it if
- You are buying on fill power
- Quills through the ticking would bother you
APSMILE Goose Feather Down Fibers Comforter, King
A feather-and-fibre blend in a reversible shell, warm across seasons by most accounts and pilling early by several.
Current price shown on Amazon. We may earn a commission.
| Fill | Feather and down fibre |
|---|---|
| Fill power | Not stated |
| Watch | Pilling reports recur |
A reversible shell and a weight owners describe as comfortable across both cool and warm nights, which is the useful thing a blend does — it splits the difference rather than committing to a season.
The concerning pattern is pilling. Several owners report the surface deteriorating early, which is a shell problem rather than a fill one, and it is the failure that decides whether this is a 2-year duvet or a 10-year one. Reports on size are split too, so check the stated dimensions against your bed rather than trusting the size name.
Buy it if
- You want natural fill without the graded-down price
- You want one weight for cool and warm nights
Don't buy it if
- Surface pilling would bother you
- You are buying on a stated fill power
Serta Goose Feather Down Fiber Comforter, Queen
Cotton-covered feather blend that owners rate warm and well-priced, and that a recurring number of them describe as audibly crinkly.
Current price shown on Amazon. We may earn a commission.
| Fill | Feather and down fibre |
|---|---|
| Cover | Cotton |
| Watch | Crinkle noise reports recur |
The cotton cover is the reason to prefer this one. A cotton shell breathes in a way a polyester one does not, and it is the same component that has to be woven tightly enough to hold a quill.
The complaint that recurs is noise. A number of owners describe an audible crinkle when the duvet moves, which points at a lining or a barrier layer inside the shell rather than at the fill. If a sound at 2am would wake you, that is the thing to weigh, not the warmth.
Buy it if
- You want a cotton shell rather than polyester
- You sleep warm and want weight without heat
Don't buy it if
- Noise at night would wake you
Down alternative has no equivalent number
Polyester fill is not rated for fill power, because the test is defined for down. It is sold instead by total fill weight or by fabric GSM, and there is no standard that lets two brands be compared directly.
Microfibre and gel-fibre polyester insulate less per ounce than down of any grade, so an equally warm polyester duvet is heavier. It is also cheaper by a wide margin, washable at home, and unbothered by the humidity that flattens down.
Rank this category by rating and then by review count and the top of it is polyester. One sits at 4.7 across 77,372 ratings and the other at 4.6 across 156,450, which is more owner evidence between them than every graded-down duvet on the marketplace combined.
Bedsure Quilted Comforter Duvet Insert
Polyester fill, Oeko-Tex certified, and the highest-rated duvet in the category across 77,372 owners — none of whom can tell you its fill power, because polyester does not have one.
Current price shown on Amazon. We may earn a commission.
| Fill | Polyester microfibre |
|---|---|
| Fill power | Not applicable |
| Care | Home machine wash |
Owners describe a weight that is warm without overheating and works across seasons, which is the polyester trade-off working in its favour: the fill does not have the loft of good down, so it does not have the heat of it either. The Oeko-Tex certification covers tested substances rather than performance, and is worth having for that reason alone.
The mixed feedback is thickness — some owners want more loft than it has. That is the honest limit of microfibre. It insulates less per ounce than down of any grade, so an equally warm version is a heavier one.
Buy it if
- It goes in your own machine
- You want one duvet for the whole year
Don't buy it if
- You want the lightest possible thing for the warmth
Utopia Bedding Comforter, King
156,450 ratings, more than every down duvet on this page combined, and owners describing polyester that feels like down — which is the honest summary of how far alternative has come.
Current price shown on Amazon. We may earn a commission.
| Fill | Polyester |
|---|---|
| Size read | 90 x 102 in, king |
| Watch | Loft reports split |
156,450 ratings makes this the most-evidenced duvet on the site, and what recurs is owners saying it feels like down. Take that seriously: polyester fill has closed most of the sensory gap, and at this price the comparison is not close.
The split is durability and loft over time, which is exactly the failure mode polyester has. Clusters compress permanently and do not recover, so a duvet that arrives lofty is finished in 2 to 5 years. Budget for replacement rather than for cleaning.
Buy it if
- You replace bedding every few years anyway
- You want weight as much as warmth
Don't buy it if
- You want a duvet that is still lofting in 2036
The real difference is service life. Polyester clusters compress permanently and clump, and most polyester duvets are finished in 2 to 5 years. A well-made down duvet holds loft for 10 to 20 with periodic airing and occasional professional cleaning.
The allergy argument is mostly about dust mites
True down allergy is rare. What people react to is far more often dust-mite allergen, and mites colonise polyester as readily as down.
Down-proof ticking works against them. Containing down requires a tightly woven cotton shell — cambric at roughly 230 threads per inch and up — and a weave tight enough to stop a down cluster escaping is also tight enough to be a poor mite habitat. A loose-weave polyester duvet is not automatically the cleaner option.
Baffle box or sewn-through decides the cold spots
Sewn-through construction stitches the top and bottom of the duvet directly together, which is cheap and creates a line of compressed fill along every seam. Those seams are cold.
Baffle box construction inserts a fabric wall between the layers so the fill can reach full loft everywhere, including at the seams. It costs more, uses more fill, and it is the single construction detail most worth paying for above 600 fill power — high-grade down cannot loft in a sewn-through shell, so the rating is wasted.
What the welfare labels cover
The Responsible Down Standard and the Global Traceable Down Standard both prohibit live-plucking and force-feeding, and both audit the supply chain rather than the finished duvet.
They differ in reach. Traceable Down traces to the parent farm; Responsible Down certifies from the farm forward. Neither is a quality claim — a certified duvet can be 500 fill power — and unlabelled down is not evidence of anything either way, only of an unaudited chain.
Which one to buy
Buy down if the duvet is a 15-year object, you want the lightest thing that will keep you warm, and you will use a cover and have it cleaned rather than washing it. Look for baffle box, a stated fill weight, and 600 fill power or above.
Buy alternative if it goes in the machine, someone in the house is unconvinced by the allergy question, or the budget is better spent elsewhere in the room — the case laid out in affordable ways to cozy up your space. For the 6 weeks of the year when a duvet alone is not enough, a heated throw costs less to run than heating the room.
The quick list
Every pick, in order. Jump to the full test on any of them.
- Highest rated
Bedsure Quilted Comforter Duvet Insert
Polyester fill, Oeko-Tex certified, and the highest-rated duvet in the category across 77,372 owners — none of whom can tell you its fill power, because polyester does not have one.
4.7from 77,372 verified reviews - Most-reviewed in the category
Utopia Bedding Comforter, King
156,450 ratings, more than every down duvet on this page combined, and owners describing polyester that feels like down — which is the honest summary of how far alternative has come.
4.6from 156,450 verified reviews APSMILE Goose Feather Down Fibers Comforter, King
A feather-and-fibre blend in a reversible shell, warm across seasons by most accounts and pilling early by several.
4.6from 2,039 verified reviewsSerta Goose Feather Down Fiber Comforter, Queen
Cotton-covered feather blend that owners rate warm and well-priced, and that a recurring number of them describe as audibly crinkly.
4.4from 4,267 verified reviewsGoose Down Fiber and Waterfowl Feather Comforter, Queen
A feather-and-fibre blend rather than graded down, which is what almost everything sold as a down comforter at this price actually is.
4.4from 9,759 verified reviews