Understanding Paper Weight and Thickness

Paper is produced by the amalgamation of cellulose composed vegetable fibers that are subsequently held together by close bonding. The fibers that are used are natural in origin, but several synthetic fibers such as polyethylene and polypropylene can be incorporated into paper to impart certain desirable physical properties. Wood pulp from pulpwood trees, especially hardwoods and softwoods like aspen and spruce are the most common source of fiber. Vegetable fiber materials come from hemp, cotton, rice and linen. Paper that is made in the west, since the revolution in the industrial sector has been exclusively wood based, except for special paper, like the one used in banknotes. Now many manufacturers are using new and environmentally friendly alternatives for making paper.   

The system of categorizing paperweight dates back to medieval Europe. It is important to understand this system, so that you can better understand a term like ‘50# offset’. Basis weight is the weight of paper in pounds, of a ream of sheet count and standardized dimensions. The sheet count and standardized dimension of papers can vary according to the type. For instance, a common copy paper sheet with a basis weight of 30 pounds will not have the same mass as the sheet of coarse paper of the same size. The standard ream of the common coy paper is 500 sheets of 17 x 22 inch paper and for coarse paper; the standard ream is 500 sheets of 24 x 36 inch paper. Historically, this convention is the result of pragmatic considerations, like the size of a sheet mold. Sheets 17 x 22 can be cut into four sheets of 8.5 x 11 inches, which is standard business stationary, used commonly. The 25 x 38 inch book-paper ream was developed because the size could be easily cut into sixteen 6 x 9 inches book-sized sheets, without any wastage.

Earlier, newsprint presses printed sheets 2 x 3 feet in size and so the newsprint ream dimension became 24 x 36 inches, with 500 sheets. Newsprint was made from the pulp of ground wood and the ground wood hanging paper or wallpaper was made on the newsprint machines. Newsprint was used as wrapping paper and for the first paper bags. Kraft pulp was used in packaging paper for greater strength. Today everyone has adopted the metric system and the grams per square system is being used as the unit that expresses the standard basis weight of all types of paperboards and paper.

According to the American measures of paperweight, the weight of paper refers to the weight of 500 sheets in the basis size that varies with the type of paper.  Some of the most common types of paper and their basis size measured in inches are:

Offset: 25 x 38
Bond: 17 x 22
Writing: 17 x 22
Index: 25-1/2 x 30-1/2
Bristol: 22-1/2 x 28-1/2
Cover: 20 x 26

The weight and grade of paper used in the copier is 20# bond. Bond papers come in a basis size of 17 x 22 although they are already trimmed to a smaller size. But 500 sheets of 17 x 22 paper used in copier would weigh 20 pounds and hence, 20# bond.