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Equivalent Weights In Paper
Commonly specified American paper weight is based on two measures:
1. BASIS WEIGHT:
The nominal weight (in pounds) of one ream (500 sheets) of a particular paper in its normal manufacturing size (basis size).
2. BASIS SIZE: The normal size of each type of paper as determined by manufacturing tradition based on common usage.

24# Bond
(17" x 22" sheet)

 50# Offset
(25" x 38" sheet)
Confusion arises because different basis sizes are used to determine the basis weight of different grades of paper. That makes direct comparison of weights between different grades difficult.
While we generally use paper in 8.5" x 11" finished sizes, it is the basis size that determines the basis weight. These are the most commonly used ‘basis sizes’:
Bond, Writing, Stationery, Ledger 17" x 22"
Cover 20" x 26"
Book, Text, Offset, Coated 25" x 38"
Index 25.5" x 30.5"
Vellum Bristol Cover 22.5" x 28.5"
Tag 24" x 36"

The chart below shows the equivalent weights between the most common grades.
The most commonly used equivalents are between bond and offset, two papers with very similar applications. A flyer might be quoted as 20# Bond by one printer and 50# Offset by another. The chart will show that they are essentially the same weight and could be used interchangeably. However, a 24# Bond would be one step heavier than 50# Offset as illustrated by the mouse at the top of the page.
You can also use the chart to determine, for example, that 60# Cover would be equal to 47# Bond, or about twice the weight of a 24# Bond letterhead.
European and Asian papers which adhere to ISO (Metric) Standards are much easier to compare among themselves. They are all measured as grams per square meter (gm/m2). Thus any two papers can be compared directly to each other without reference to sheet or basis size.

Bond

Offset, Book & Text

Cover

Vellum Bristol Cover

Index

Tag

ISO-
(Metric)

Basis Size*

17" x 22"

25" x 38"

20" x 26"

22.5" x 28.5"

25.5" x 30.5"

24" x 36"

grams/
meter2

Bond, Duplicator, 13 33 18 22 27 30 49
Ledger, Mimeo 15 38 21 25 31 35 56
& Writing 16 41 22 27 33 37 60
20 51 28 34 42 46 75
24 61 33 41 50 55 90
28 71 39 48 58 65 105
32 81 45 55 67 74 120
36 91 50 62 75 83 135
Book, Offset & 16 40 22 27 33 36 59
Text 18 45 25 30 37 41 67
20 50 27 34 41 45 74
24 60 33 40 49 55 89
28 70 38 47 57 64 104
30 75 41 50 61 68 111
31 80 44 54 65 73 118
35 90 49 60 74 82 133
39 100 55 67 82 91 148
47 120 66 80 98 109 178
Cover 36 91 50 62 75 83 135
(Uncoated, Antique 43 110 60 74 90 100 162
Finish) 47 119 65 80 97 108 176
58 146 80 99 120 133 216
65 164 90 111 135 150 243
72 183 100 124 150 166 270
Vellum Bristol 33 85 46 57 69 77 125
Cover 39 100 54 67 81 91 147
47 120 65 80 98 109 175
Index 43 110 60 74 90 100 163
53 135 74 91 110 122 199
67 170 93 115 140 156 253
Tag 43 110 60 74 90 100 163
54 137 75 93 113 125 203
65 165 90 111 135 150 244
76 192 105 130 158 175 285
87 220 120 148 180 200 326
* BASIS SIZE is the common manufactured sheet size in a particular grade of paper. The paper’s weight (bold figures) is based on the weight in pounds of one ream (500 sheets) of that paper in it’s basis size.
For example, “20# Bond” is based on the fact that 500 sheets of that grade (one ream) in 17" x 22" size (basis size) would weight 20 pounds. By quick calculation, you can conclude that 500 sheets of 20# Bond in 8.5" x 11" size (1/4 of 17" x 22" sheet) would weight 5 pounds.

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