There have been many standard sizes of paper at different times and in different countries.
The international standard is ISO 216, which defines amongst other, A4. ISO paper sizes are all based on a single aspect ratio of the square root of two, 1:1.4142. The largest standard size, A0, has an area of 1 m². A1 is formed by cutting a piece of A0 in half, which retains the aspect ratio. This particular measurement system was chosen in order to allow folding of one standard size into another, which cannot be accomplished with traditional paper sizes.
The ISO B series is a scaling of the A series, B1 is half way between A0 and A1 in size. The C series is half way between the A and B series of the same number, for instance, C0 is half way between A0 and B0. This way C0 is slightly larger than A0, and B0 slightly larger than C0. This was intended to allow one to fit inside an envelope of the other. For instance, a letter written on A4 paper, the standard for this role, fits inside a C4 envelope. A C4 envelope can fit inside a B4 envelope.
Sizes larger than A0, B0 and C0 are defined by putting a number in front of the letter (so 1A is twice the size of A0).
International standard paper sizes are now used in all countries except the United States and Canada.
| Name | Size (mm) | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| A0 | 841 × 1189 | B0 | 1000 × 1414 | C0 | 917 × 1297 | ||||
| A1 | 594 × 841 | B1 | 707 × 1000 | C1 | 648 × 917 | D1 | 545 × 779 | ||
| A2 | 420 × 594 | B2 | 500 × 707 | C2 | 458 × 648 | D2 | 385 × 545 | ||
| A3 | 297 × 420 | B3 | 353 × 500 | C3 | 324 × 458 | D3 | 272 × 385 | E3 | 400 × 560 |
| A4 | 210 × 297 | B4 | 250 × 353 | C4 | 229 × 324 | D4 | 192 × 272 | E4 | 280 × 400 |
| A5 | 148 × 210 | B5 | 176 × 250 | C5 | 162 × 229 | D5 | 136 × 192 | E5 | 200 × 280 |
| A6 | 105 × 148 | B6 | 125 × 176 | C6 | 114 × 162 | D6 | 96 × 136 | E6 | 140 × 200 |
| A7 | 74 × 105 | B7 | 88 × 125 | C7 | 81 × 114 | D7 | 68 × 96 | ||
| 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 |
| Name | Size (inches) | Size (mm) |
|---|---|---|
| Quarto | 10 × 8 | 254.0 × 203.2 |
| Foolscap | 13 × 8 | 330.2 × 203.2 |
| Letter | 8.5 × 11 | 215.9 × 279.4 |
| Legal | 8.5 × 14 | 215.9 × 355.6 |
| Ledger / Tabloid | 11 × 17 | 279.4 × 431.8 |
| Executive | 7.25 × 10.5 | 184.15 × 266.7 |
| Post | 15.5 × 19.25 | 393.7 × 488.95 |
| Crown | 15 × 20 | 381.0 × 508.0 |
| Large post | 16.5 × 21 | 419.1 × 533.4 |
| Demy | 17.5 × 22.5 | 444.5 × 571.5 |
| Medium | 18 × 23 | 457.2 × 584.2 |
| Royal | 20 × 25 | 508.0 × 635.0 |
| Elephant | 23 × 28 | 584.2 × 711.2 |
| Double Demy | 23.5 × 35 | 596.9 × 889.0 |
| Quad Demy | 35 × 45 | 889.0 × 1143.0 |
| A | 8.5 × 11 | 215.9 × 279.4 |
| B | 11 × 17 | 279.4 × 431.8 |
| C | 17 × 22 | 431.8 × 558.8 |
| D | 22 × 34 | 558.8 × 863.6 |
| E | 34 × 44 | 863.6 × 1117.6 |
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