What the labels mean
Down Jacket Fill Power, Explained
Fill power is loft per ounce — cubic inches one ounce of down occupies. Fill weight is how many ounces are in the jacket. You need both numbers.
Updated 27 Aug 2026 · 6 min read · down jacket fill power explained
Loft per ounce, not a quality slogan
Higher fill power means larger, stronger clusters and more trapped air per gram. That is warmth-to-weight and compressibility. It is not automatically “warmer” if the brand put less down in the baffles. Two numbers: FP and fill weight (grams or ounces of down in the whole garment, sometimes listed as “fill weight 80 g”).
How to read a hangtag
RDS or Responsible Down is a supply-chain standard, not a warmth spec. 80/20 down/feather is a blend; more feather is heavier and pokier. Box baffles loft better than sewn-through at the stitch lines. A city packable 800-fill vest at 70–90 g fill, $150–$250, is a real layer. A 600-fill parka at 250 g fill, $180–$300, is the winter coat.
| Fill power | What it means | Typical use |
|---|---|---|
| 500–600 | Good clusters, heavier for the warmth | Budget puffer, $80–$160 |
| 700 | Very good | Daily winter, $150–$280 |
| 800–850 | Excellent loft/weight | Packable, alpine, $220–$450 |
| 900+ | Rare, diminishing returns for cities | Ultralight specialist |
Wet down is a wet sweater
Untreated down clumps when soaked. Hydrophobic (DWR-treated) down delays that. For rainy commutes, a shell over the puffer beats trusting 800-fill in a downpour. Down-alternative in a jacket is heavier for the warmth; it is the wet-city or wash-often choice, not a fake 800.
Questions, answered
- Is 800-fill twice as warm as 400-fill?
- No. It is about twice the loft per ounce. Warmth is FP times how much down is in the jacket, plus the shell and your layers.
- Why won’t brands print fill weight?
- Because a high FP with low fill weight photographs like a cloud and performs like a shirt. Ask, or weigh reviews that cut the baffles.
- Goose or duck?
- Goose more often reaches 800+. Good duck 700 is a real jacket. Species is secondary to FP, fill weight, and construction.
