Clearly having too much time on my hands, I found myself wondering if there’s an “objective” way to compare down-filled jackets. There’s no EN rating similar to that used for sleeping bags; I’m not sure you can have sufficient testing controls to do that with jackets since the full body isn’t encased.

I did wonder if multiplying fill factor times amount of fill might be a rough guideline as to which was warmer for garments of similar design. For example, if you were looking at two waist-length hooded jackets with full-length zippers, elastic cuffs, adjustable hood, and drawcord or elastic waist, how would you know whether the one with 12 ounces of 700-fill down is warmer or colder than the one with 9 ounces of 900-fill down.

One thing that came to mind is multiplying quantity of down times fill power to estimate the insulating value of each. In the example above, the 700-fill jacket would have a “factor” of 8400 (12x700) while the 900-fill jacket would have a “factor” of 8100 (9x900) - and the rough estimate would indicate that the 700-fill jacket might be marginally warmer.

I realize that there are a lot of qualitative factors that can affect warmth (how well each shell blocks wind, whether the “cut” of the jacket allows the down to fully loft, etc.)

Any thoughts on a rough-and-ready method to estimate this? If there is, it would certainly make it easier to compare garments when you can’t try them on, such as when you’re looking at a website or catalogue (remember those?)