honestly what I'd do is make a pitcher of that juice, probably 2 quarts, so a half gallon. take a hydro reading in the pitcher, divide by 2, and that's the gravity points it will all at 1 can per gallon.
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