I have the same problem - I'm trying to enter my Diet Coke into my custom foods and have 355mL, now I found this: "Milliliters into Grams: Multiply the specific gravity of the substance by the number of milliliters, to obtain the weight in grams." Uh... how the heck to I get the specific gravity? Does anyone just happen to know how many grams are in a 12 fl oz can of pop?