Down Filling Power Explained: 600 vs 700 vs 800 Fill Power
Fill power is the single most-cited specification in down outerwear sourcing — and the most misunderstood. This guide explains what fill power measures, how it is tested, and what specs make sense for different product tiers.
What is Fill Power?
Fill power measures the loft (volume in cubic inches) of one ounce of down under standardized compression. Higher numbers mean more loft per gram of down, which translates to more warmth for the same weight. A 700-fill-power jacket will be warmer per gram of fill than a 600-fill-power jacket of identical design.
Standard Testing Methods
The two most accepted methods are IDFB (International Down and Feather Bureau) and EN 12130. IDFB is the more widely accepted international standard; results from one method are not directly comparable to the other.
Practical Specs by Product Tier
- 500-600 fill: entry-level puffers and city jackets, where weight is less critical and price is key.
- 650-750 fill: the sweet spot for most premium outerwear — excellent warmth-to-weight ratio at sustainable cost.
- 800+ fill: ultralight alpine and expedition gear, where every gram matters.
Down vs Feather Ratio
Fill power measures only the down cluster portion. A 90/10 down-feather ratio with 700 fill power means 90% of the fill (by weight) is down cluster and 10% is small feather. Higher down content generally means higher fill power, but the cluster quality also matters.
Compliance & Certification
For EU markets, down must carry DOWNPASS, RDS (Responsible Down Standard) or Global Traceable Down Standard certification. These address animal welfare and traceability. Right Suntone Trading sources only certified down for export orders.
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