A Unit Price is useful for value comparisons by consumers, only if its numerical expression does not change with package size, and the numerical value does not deviate for the identical product of any package size at other nearby stores.
Widespread uniformity of the units of the Unit Price for the given product is essential to enable this objective. This requirement limits the choice of units, primarily, for example, to “cents per gram” or to “cents per milliliter (for fluids).” This requirement can not be satisfied by the incoherently related non-metric choices permitted in NIST SP 1181. For example, price per fluid ounce, and price per pint, and price per quart, and price per gallon must not be accepted, at the discretion of each independent store manager. Eugene Mechtly
