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Goose down is not automatically warmer than duck down. What makes a jacket warm is how much air the down traps, and that depends on three numbers on the label: fill power, fill weight and the down-to-feather ratio. The bird matters, but less than most marketing suggests.
Down is a natural fiber that is washed, sorted and finished before it ever reaches a jacket, and those wet-processing steps are my field: I have worked in textile wet processing for 14+ years. Here is how to read the label and decide which down is worth paying for.
Goose down vs duck down at a glance
| Goose down | Duck down | |
|---|---|---|
| Cluster size | Usually larger | Usually smaller |
| Typical fill power | About 600 to 900+ | About 550 to 750 (top grades reach higher) |
| Warmth for its weight | Higher at the top grades | Very good at mid grades |
| Loft over years | Large clusters tend to keep their loft | Good, if well cleaned and cared for |
| Smell risk | Low when cleaned properly | Low when cleaned properly; poorly washed down can smell |
| Price | Higher | Lower |
| Best for | The lightest, warmest jackets for the weight | Good-value everyday jackets |
What is down, exactly?
Down is the soft under-plumage of waterfowl: a three-dimensional cluster with a small center and hundreds of fine filaments radiating out. It has no hard quill. Those filaments trap still air, and still air is what keeps you warm. Feathers, by contrast, are flat with a quill. They add weight and some structure but trap far less air.
Larger birds that grow for longer tend to produce larger, more mature clusters. Geese are larger than ducks, which is why the very highest fill powers are usually goose down. But a mature duck cluster can outperform an immature goose cluster, which is why the label number matters more than the bird.
What fill power really means
Fill power measures loft: how much space one ounce of down fills, in cubic inches, after it is allowed to expand in a test cylinder. An ounce of 800-fill down fills about 800 cubic inches. Higher fill power means each gram traps more air, so the jacket can be warmer for the same weight, or lighter and more packable for the same warmth.
- 550 to 650: everyday jackets and coats. Warm, but bulkier for the warmth.
- 650 to 750: a good balance of warmth, weight and price.
- 800 and above: premium, very light and compressible. Mostly goose down.
One caution: fill power is measured with different methods in different regions, and the same down can test lower under the European method than under the US one. Compare numbers from the same market.
Fill power vs fill weight: the number brands leave out
Fill power is quality. Fill weight is quantity: how many grams or ounces of down are inside. A jacket with 100 g of 650-fill down can be warmer than one with 60 g of 850-fill. When a brand lists both, you can judge warmth properly. When it lists only fill power, the jacket may be light on fill.
Down-to-feather ratio
Labels such as 90/10 or 80/20 give the share of down clusters to small feathers. More down means more loft and less weight. Feathers poke through shells more easily and lose loft sooner. For a quality jacket, look for at least 80/20, and 90/10 or better at higher prices.
Responsible down: what RDS means
The Responsible Down Standard (RDS) and similar certifications audit the supply chain for animal welfare, including a ban on live-plucking and force-feeding. They say nothing about warmth, but they are a sign that the supply chain is traceable. Many quality brands now use certified down for both goose and duck.
Hydrophobic (water-resistant) down
Some down is treated with a water-resistant finish so it keeps more loft in damp conditions and dries faster. It helps in wet climates, but it does not make a jacket waterproof. A good shell matters more. Read our guide on how to wash a down jacket to keep both the down and the shell working.
Which should you buy?
- For the lightest, most packable warmth: high-fill goose down (800+).
- For a city jacket or daily commuter: good duck down at 600 to 700 fill is excellent value.
- For wet climates: either, with a water-resistant shell, or consider synthetic insulation.
- On any label: check fill power, fill weight and down ratio before the bird.
See how these numbers play out in real jackets in our guide to the best down jackets for men.
Frequently asked questions
At the same fill power and fill weight, they are very similar. Goose down reaches higher fill powers more often, so the warmest-for-weight jackets are usually goose down. Yes. 650 is a solid mid-range fill power for everyday winter jackets. Higher numbers mainly make the jacket lighter and more packable for the same warmth. Usually because of moisture combined with residue in poorly cleaned down, or a jacket stored damp. Washing with a down wash, rinsing well and drying fully usually fixes it. It means about 90% down clusters and 10% small feathers by weight. Higher down content gives more loft and less weight.Is goose down warmer than duck down?
Is 650 fill power good?
Why does my down jacket smell?
What does 90/10 mean on a down jacket?