You simply should NOT convert weight to volume, for the reasons already mentioned. Even priming sugar is sold by weight, not volume...and the people that measure by volume are usually the ones complaining about inconsistent carbonation. I.e. 'this batch has too much fizz...the last one didn't have enough, but I used the same 2/3cup of dextrose'.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10