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How to Convert the Basis Weight of Paper to GSM


There are two methods to indicate the weight of paper, basis weight (or English) and European. While the basis method is more commonly known, it has its drawbacks. Therefore, for a more accurate comparison between different types of paper, the European method can be utilized. However, a conversion from basis to gsm is necessary.

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1£®Know that the basis weight of paper is specified as the fixed weight, measured in pounds, of 500 sheets in a particular paper's basic sheet size. However, as there are different types of paper, there are different "basic sheet sizes" for each type. The thickness of a sheet of paper or caliper (represented in thousandths of an inch) is measured with a micrometer. The greater the caliper or thickness of each individual sheet, the greater the basis weight.

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2£®Know that the European method of expressing paper weight measures one sheet of paper based on two-dimensional height and a designated width of one meter. While the method describes a hypothetical meter, its main strength is a more accurate comparison between heavily varying types of paper. The basis method does not factor in different dimensions, and therefore, the weight of thick letter paper may be the same as extremely thin paper that has significantly greater dimensions.

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3£®Note what type of paper you are converting.
1 lb. of Text paper is equivalent to 1.48 gsm.
1 lb. of Cover paper is equivalent to 2.708 gsm.
1 lb. of Index paper is equivalent to 1.81 gsm.
1 lb. of Vellum is equivalent to 2.91 gsm.
1 lb. of Tag paper is equivalent to 1.63 gsm.
1 lb. of Bond paper is equivalent to 3.69 gsm.
1 lb. of Bristol is equivalent to 2.19 gsm.
To convert, multiply the basis weight in pounds times the equivalent gsm for the specific type of paper.