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This page is a translator with many practical applications. Film extruders invoice by the roll, thousand square centimeters, the bag or the kilogram. In the final analysis, we buy kilograms and sell kilograms.
The custom of invoicing by the kilogram can be especially confusing to users of film who need to know how to convert kilograms into area or per package unit weight. Conversion factors which are general knowledge in bagmaking, printing and laminating are generally not available to the industrial consumer. The following information bridges the gap and makes it easy to derive weight per 1,000 packages.
Among other uses, this information provides the formulas you need to audit your supplier for what is known as yield. Many extruders abuse the information asymmetry and industry tolerance of ±10%. When invoicing by the kilogram, they sell heavy film replete with tare weight. The invoice has a low price and the true cost is often 15% more. When invoicing by the piece, the gauge is almost always light.
The industrial audience often cannot grasp how a savings can be achieved by paying a higher price per kilogram for a reduced gauge film simply because they do not have the conversion factors. To capture the true cost of shrink film, the transverse direction ( TD ) shrinkage must be taken into account. By allowing the latitude of 7 to 12% TD shrinkage, the extruder sells more film than if the shrinkage is 0 to 3%. A percent saved is a percent saved.
Because we cannot know the eventual package dimensions, all of our orders are measured in weight per 1,000 linear metres, or yield. The calculation for every order appears on all paperwork from acknowledgement to packing list. In other words, we are honest about yield and give customers the tools to audit. | 
