When setting up inventory values for items/purchase units in CNCentral, users have the option to enter the nominal weight of the purchase unit. In some cases this information is supplied by the manufacturer via GDSN but in the case of generic produce, this value is often setup as 1 LB and left up to the District Administrator to edit according to the purchase unit information from the distributor.
The nominal weight is the weight of the package that you purchase from your distributor. For example, a 5 LB package of shredded cabbage would have a nominal weight 5 LBs. The calculated net weight of a purchase unit is determined based on the serving size in grams multiplied by the number of servings per purchase unit. The calculated net weight is essentially the weight of the item as it would be used on a menu. In some cases, like with fresh produce, the calculated weight is determined and defined by the USDA's Food Buying Guide.
The calculated net weight is a read-only value in CNCentral that can be adjusted when the total number of servings per purchase unit is adjusted. It will always be proportional to the servings per purchase unit.
There may be times when the calculated net weight may be different than the Nominal Net Weight due to rounding errors or other factors where the serving size does not correspond directly to the nominal weight. An example of the serving size not corresponding to nominal weight might be purple cabbage, raw where the USDA Food Buying Guide has the servings per pound defined as 24.6 and each serving is 17.5 grams. 24.6 x 17.5 = 430.5 but there are 453.6 grams per lb so the calculated net weight for red cabbage, raw is .949 (430.5 / 453.6 = .949).
Another example is drained weight for canned items. The serving size of the item as used on a menu would be as drained while the nominal net weight would include the liquid. The calculated net weight would accommodate this difference so that correct # servings per purchase unit can be entered.