## How Many? A Dictionary of Units of Measurement © Russ Rowlett and the University of North Carolina at Chapel Hill Table of Contents About the Dictionary Using the Dictionary ISO Standard Paper Sizes

Data from Markus Kuhn, International Standard Paper Sizes. See this site for a complete discussion of how the ISO 216 paper sizing system works. This system is used in most of the world, replacing traditional paper sheet sizes such as the 8.5 by 11 inch size familiar in the U.S. (See this link for information on the traditional paper sizes.)

In brief, international paper sizes are in three series, designated An, Bn, and Cn. Increasing the number n by 1 halves the area of the sheet, so that, for example, an A5 sheet is an A4 sheet cut in half. The basic sheet A0 has an area of 1 square meter, so an A4 sheet (the standard size for business letters) has an area of 1/16 square meter. The ratio between the height and width of a sheet is always the square root of 2 (about 1.414).

The area of a Bn sheet is the area of the An sheet multiplied by the square root of 2, so a B5 sheet, for example, is intermediate in size between an A4 and an A5 sheet. The Cn size, intended mostly for envelopes, has an area equal to the fourth root of 2 (about 1.189) times the area of the An sheet, which means that an An sheet fits nicely, unfolded, in a Cn envelope.

The dimensions of the sheets are computed from these formulas:

Format

Width [m]

Height [m]

An

2-1/4-n/2

21/4-n/2

Bn

2-n/2

21/2-n/2

Cn

2-1/8-n/2

23/8-n/2

With roundoff, the dimensions (in millimeters) are as follows:

A Series Formats

B Series Formats

C Series Formats

4A0

1682 × 2378

-

-

-

-

2A0

1189 × 1682

-

-

-

-

A0

841 × 1189

B0

1000 × 1414

C0

917 × 1297

A1

594 × 841

B1

707 × 1000

C1

648 × 917

A2

420 × 594

B2

500 × 707

C2

458 × 648

A3

297 × 420

B3

353 × 500

C3

324 × 458

A4

210 × 297

B4

250 × 353

C4

229 × 324

A5

148 × 210

B5

176 × 250

C5

162 × 229

A6

105 × 148

B6

125 × 176

C6

114 × 162

A7

74 × 105

B7

88 × 125

C7

81 × 114

A8

52 × 74

B8

62 × 88

C8

57 × 81

A9

37 × 52

B9

44 × 62

C9

40 × 57

A10

26 × 37

B10

31 × 44

C10

28 × 40

Note: To convert the dimensions to inches, divide by 25.4. Thus an A4 sheet measures 8.27 by 11.69 inches, making it a little taller and narrower than an 8.5 by 11 inch sheet.