UNDERSTAND IT VISUALLY
Three numbers. Three different questions.
Down percentage describes composition, fill power describes measured loft, and fill weight describes mass. Keep all three in the brief.
A single number cannot rate a finished jacket’s warmth.
Composition: what is in the fill?
A down/feather percentage is a composition claim. It should be tied to a recognized test and the destination market’s labeling requirements.
Fill power: how much volume does a mass of down occupy?
Fill power measures loft under controlled test conditions. The reported result depends on the test cylinder, units, sample conditioning and method. Compare like with like: same method, units, and conditioning.
Fill weight: how much filling is used?
Fill weight is the net mass of filling. A jacket’s total fill weight does not tell you whether insulation is distributed evenly. Panel-level targets can help teams develop different insulation zones and repeat a sample.
A useful specification line
Record composition and supporting method, fill-power method and units, total fill weight, panel fill map, and approved tolerance. Then evaluate the finished jacket for the intended climate and layering system.
Questions buyers ask
Can I compare two fill-power numbers directly?
Only after confirming that units, cylinder, and conditioning method are comparable.
Which number tells me jacket warmth?
No single number does. A useful evaluation considers fill composition, fill power, fill mass and distribution, garment construction, fit, and intended conditions.
Sources and further reading
External sources inform the technical explanations above. Standards and test requirements can vary by market; check current documents for your product.
This guide supports early product decisions. Confirm material data, applicable labeling rules and performance claims for the specific product and destination market.