Originally Posted by The Wolf in a Hammock
im a bit confused with this equation, are you multiplying the length and width together before you divide everything else by it, resulting in this equation
(Fill power x Ounces down)/(LxW)
or are you dividing by one and then taking the value and dividing it by the other resulting in this equation
((Fill power x Ounces down)/(L))/(W)
or are you simply adding L&W together resulting in
(Fill power x Ounces down)/(L+W)
Also, 18*F from what, 100* 75*, assuming you subtract this
The first two options are what I meant - they give identical results.
The 18* per inch comes from WesternMountaineering's tables and the product of the 18xinches is subtracted from 67*, again from WM's tables. WM is one of the most highly respected sleeping bag manufacturers, but they are not cheap (I know, I own two of them).