Historically, this convention is the product of pragmatic considerations such as the size of a sheet mold.īy using the same basis sheet size for the same type of paper, consumers can easily compare papers of differing brands. These "uncut" basis sizes are not normally labelled on the product, are not formally standardized, and therefore have to be guessed or inferred somehow from trading practice. The standard dimensions and sheet count of a ream vary according to the type of paper. ![]() the dimensions of an "uncut" sheet in that ream.So, to compute the mass per area, one must know Often, that is a size used during the manufacturing process before the paper is cut to the dimensions in which it is sold. Instead, it is the mass of the uncut "basis ream" in which the sheets have some larger size (parent size). However, the mass specified is not the mass of the ream that is sold to the customer. In the US system, the weight is specified in avoirdupois pounds and the sheet count of a paper ream is usually 500 sheets. ![]() The basis weight of paper is the density of paper expressed in terms of the mass of a ream of given dimensions and a sheet count. In countries that use American paper sizes, a less verifiable measure known as basis weight is used in addition to or instead of grammage. Typically grammage is measured in paper mill on-line by a quality control system and verified by laboratory measurement. The abbreviation "gsm" instead of the standard "g/m 2" symbol is also widely encountered in English-speaking countries. Typical office paper has 80 g/m 2 (0.26 oz/sq ft), therefore a typical A4 sheet ( 1⁄ 16 of a square metre) weighs 5 g (0.18 oz). Grammage = mass (g) length ( m ) × width ( m ) This quantity is commonly called grammage in both English and French, though printers in most English-speaking countries still refer to the " weight" of paper. In the metric system, the mass per unit area of all types of paper and paperboard is expressed in terms of grams per square metre (g/m 2 or gsm or g/sm). Japanese paper is expressed as the weight in kilograms (kg) per 1,000 sheets. The convention used in the United States and a few other countries using US-standard paper sizes is pounds (lb) per a ream of 500 (or in some cases 1000) sheets of a given (raw, still uncut) basis size. Expressed in terms of the mass per number of sheets of a specific paper size, known as basis weight.It is often notated as gsm on paper product labels and spec sheets. This is the measure used in most parts of the world. Expressed in grams (g) per square metre (g/m 2), regardless of its thickness ( caliper).Two ways of expressing grammage are commonly used: ![]() Grammage and basis weight, in the pulp and paper industry, are the area density of a paper product, that is, its mass per unit of area. For the heavy desktop object, see paperweight.
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