Divide the price you pay per bulk unit by the number of use units in the bulk unit and designate the use unit and its cost in inventory.
Example 1: I pay $46.00 for a 55 lb. sack of grain. The unit I use when adding grain to a recipe is pounds. When I enter the grain into inventory I want to price it by the pound. $46.00/55 = .836, so I enter my cost/lb. as $.84.
Example 2: I pay $12.00 for a pound of Cascade hops. The unit I use when adding hops to a recipe is grams. There are about 453 grams per pound, so I divide the cost of the 1 lb. package by 453 to get the cost per gram: $12.00/453 =.026, so I enter my cost/lb. as $.03
There are ingredients that I don't always buy in bulk and want to have 2 cost levels for use. In those cases, when I add the item into inventory, I designate them as both bulk purchased and purchased by the use unit in separate listings.
Example:
Sack Rahr 2-row malt $.86 Rahr 2-row malt $1.08