Paper and Envelope Sizes

The most common system of paper sizes in Europe is the ISO standard. Most people are familiar with the A series which includes A4 (highlighted on the chart) the usual letterhead size. The C series is for envelopes - A C4 envelope being ideal for holding an A4 sheet. There is also a B series which provides intermediate sizes for the A series but this is rarely used. DL is a special size for envelopes designed to accept A4 paper folded in three. All sizes are given in millimetres

 
Sheet
size

 A

 B

 C

 RA

 SRA

  0

 841 x 1189

 1000 x 141

 917 x 1296

 860 x 1220

 900 x 1280

  1

 594 x 841

 707 x 1000

 648 x 917

 610 x 860

 640 x 900

  2

 420 x 594

 500 x 700

 458 x 648

 430 x 610

 450 x 640

  3

 297 x 420

 353 x 500

 324 x 458

 305 x 430

 320 x 450

  4

 210 x 297

 250 x 353

 229 x 324

 215 x 305

 225 x 320

  5

 148 x 210

 176 x 250

 162 x 229

 152 x 215

 160 x 225

  6

 105 x 148

 125 x 176

 114 x 162

 107 x 152

 112 x 160

  7

 74 x 105

 88 x 125

 81 x 114

 76 x 107

 80 x 112

  8

 52 x 74

 62 x 88

 57 x 81

 53 x 76

 56 x 80

The aspect ratio of ISO paper sheets is 1 to 1.414 (The square root of 2). This gives them a unique property: If you cut a sheet into two the resulting halves are the same proportion as the original. In other words a sheet of A4 when halved gives you two sheets of A5. All A size papers have the same proportions. The largest sheet in this series is A0 which is 841mm x 1189mm and just happens to be one square metre in area (ISO paper sizes are rounded to the nearest millimetre). Two other series which you may come across are RA and SRA which are used by printers. They are slightly larger than the A series to provide for grip, trim and bleed.