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TAPPI T 410 Basis weight






Grammage of paper and paperboard (weight per unit area)


TAPPI T 410 Basis weight provides the industry with a way to measure and report the mass per unit area of a paper product. In the United States the customary or commercial term for expressing the “weight” per unit area (more properly “mass per unit area”) of paper has been “basis weight,” “ream weight,” or “substance.” These are defined as the mass in pounds of a ream of a given sheet size and number of sheets (usually 500 sheets, occasionally 480 sheets). In most other countries the mass per unit area is expressed in grams per square meter, g/m2. The French term for mass per unit area, “grammage,” is recommended by ISO Committee TC 6 on Paper for use in English as well as in French because of its convenience and clear relationship to g/m2.


The area of several sheets of the paper or paperboard is determined from linear measurements and the mass (commonly called “weight”) is determined by weighing. The grammage is calculated from the ratio of the mass to the area after conversion to metric units when necessary.


Most paper is bought and sold in accordance with its mass per unit area, and therefore the grammage has great significance both to the consumer and the producer in defining price. The values of many physical properties such as bursting strength, thickness, and bulk are interpreted and specified with regard to grammage. The grammage is also used to calculate the index properties of many strength properties and thus the proper measurement of basis weight is critical for the correct calculation of these indexes.

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