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152 Chapter 5 – Media specifications EN
U.S. paper grades
The U.S. paper grading system has evolved from custom and usage
rather than from a technical background, resulting in similar papers
having different stated weights. For example, a 24# bond paper is
exactly the same weight as a 60# book or a 60# text or a 33# cover.
This is because basis weight is defined as the weight of 500 sheets of
paper cut to basic size. The basic size for bond, book/text, cover, index,
bristol, and tag are all different so the given weights for these paper
grades might be different although the physical weight is virtually
identical. The following tables will help clarify these differences. Note
the difference in basic size for each grade, which affects the weight of
500 sheets of that grade:
Grain long grain
Note
If paper is greater than 135 g/m2 (36 lb)
use short grain.
Moisture content 4 percent to 6 percent by weight
Smoothness 100 to 250 Sheffield
U.S. paper grades: basic sizes and basis weights
Paper
grade
Basic size Basic area Factor Equivalent
basis
weights
(example)
Bond 17 by 22 in 374.0 sq.in 1.00 24# bond
Text 25 by 38 in 950.0 sq. in 2.54 61# text
Book (coated
or uncoated)
25 by 3 in 950.0 sq. in 2.54 61# book
Cover 20 by 26 in 520.0 sq. in 1.39 33# cover
Bristol 22.5 by 28.5 in 641.25 sq. in 1.71 41# bristol
Index 25.5 by 30.5 in 777.75 sq. in 2.08 50# index
Paper specifications (continued)
Category Specification