Understanding International Standard Paper Sizes

Understanding International Standard Paper Sizes
Jul 07

All paper is not created equal, and when it comes to paper sizes, there is no such thing as a consistent, global measurement format. What we consider “standard” paper sizes in the United States, does not equate to what other countries across the world would consider standard. Consider the following chart, which compares “standard” U.S. and International paper sizes:

 

U.S. Paper Type

U.S. Size (inches)

International Paper Type

International Size (inches)

Letter

8.5 x 11

A4

8.27  x 11.69

Tabloid

11 x 17

A3

11.69 x 16.54

Legal

8.5 x 14

N/A

8.5 x 14

Half Letter

8.5 x 5.5

A5

5.83 x 8.27

Postcard

6 x 4

A6

4.13 x 5.83

Business Card

3.5 x 2

N/A

3.35 x 2.13

Poster

11 x 14

DL

11.69 x 16.64

 

While every country has not agreed on a standard paper size, there is consistent utilization among many countries of the International Standard Paper Size model. These standard international sizes are based on what is known as the ISO paper size concept, which bases the height-to-width ratio of all pages on the square root of two. Put differently, the width and the height of a page relate to one another as would the side and the diagonal of a square. Known as an aspect ratio, this concept makes defining standard paper sizes geometrically simplistic.

For those of us in the United States, it is important to realize that ISO paper sizes are based on the metric system. Since the “square root of two” concept does not result in evenly rounded numbers, ISO standard paper sizes are identified by the letter A, and a corresponding number, rather than by a defining name or dimension as we do in the united states (i.e.: Tabloid, or 8.5 x 11). More specifically, the ISO naming convention is based on the idea that the height of the page divided by the width of all formats is the square root of two. Therefore:

  • Size A0 has an area of one square meter
  • Size A1 is A0 cut into two equal pieces, or rather the height of A1 is the width of A0, and the width of A1 is half the height of A0. 

All smaller sizes progress using the same measurement and ratio approach described above.

 To accommodate instances where the ISO A series formula does not properly accommodate a specific size need, the ISO approach has created a B series of standard sizes, as well as a C series, which defines envelope sizes.

Still using a mathematical ratio formula to define its size categories, in the B series, the width and height are the geometric average between an A size and the next larger A size. For example, B1 is the geometric average of A1 and A0. Similarly, the C series is calculated as the geometric average between the A and B series format.

 Refer to the following table for ISO A, B, and C comparative dimensions (in millimeters):

 

A Series

B Series

C Series

4A0

1682 x 2378

N/A

 

N/A

 

2A0

1189 x 1682

N/A

 

N/A

 

A0

841 x 1189

B0

1000 x 1414

C0

917 x 1297

A1

594 x 841

B1

707 x 1000

C1

648 x 917

A2

420 x 594

B2

500 x 707

C2

458 x 648

A3

297 x 420

B3

353 x 500

C3

324 x 458

A4

210 x 297

B4

250 x 353

C4

229 x 324

A5

148 x 210

B5

176 x 250

C5

162 x 229

A6

105 x 148

B6

125 x 176

C6

114 x 162

A7

74 x 105

B7

88 x 125

C7

81 x 114

A8

52 x 74

B8

62 x 88

C8

57 x 81

A9

37 x 52

B9

44 x 62

C9

40 x 57

A10

26 x 37

B10

31 x 44

C10

28 x 40

        

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