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International Styles & Standards
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In an effort to standardize paper/envelope sizes, the International Standards Organizations (ISO) has developed a system that has been adopted by many metric-standardized countries. The standard is based upon the principle that a rectangle's sides have a ratio of 1:2. If you cut in half any sheet with these proportions, it will always yield two new sheets with the same proportions. There are three ISO series: A, B, and C, and each has a suffix which denotes the size. The lower the number, the larger the size.
Select a envelope below to view chart of standard ISO sizes.
ISO Envelopes: Sheets from the A series can be inserted in the C series envelope, flat or folded. For example, a C5 envelope will accomodate an A5 sheet flat or an A4 folded once. A listing of ISO envelope sizes follows. All are taken from B or C size sheets. View Sizes
| Name |
Envelope size (mm) |
| C3 |
324 x 458 |
| B4 |
250 x 353 |
| C4 |
229 x 324 |
| B5 |
176 x 250 |
| C5 |
162 x 229 |
| B6/C4 |
125 x 324 |
| B6 |
125 x 176 |
| C6 |
114 x 162 |
| DL |
110 x 220 |
| C7/6 |
81 x 162 |
| C7 |
81 x 114 |
A Series, General Print: Used for the majority of printed material — stationery, business cards, brochures, mailers and manuals. View Sizes
| Name |
Envelope size (mm) |
| A0 |
841 x 1189 |
| A1 |
594 x 841 |
| A2 |
420 x 594 |
| A3 |
297 x 420 |
| A4 |
210 x 297 |
| A5 |
148 x 210 |
| A6 |
105 x 148 |
| A7 |
74 x 105 |
| A8 |
52 x 74 |
| A9 |
37 x 52 |
| A10 |
26 x 37 |
B Series, Posters & Wallcharts: An alternative to the A series. Ideal for posters and wallcharts. View Sizes
| Name |
Envelope size (mm) |
| B0 |
1000 x 1414 |
| B1 |
707 x 1000 |
| B2 |
500 x 707 |
| B3 |
353 x 500 |
| B4 |
250 x 353 |
| B5 |
176 x 250 |
| B6 |
125 x 176 |
| B7 |
88 x 125 |
| B8 |
62 x 88 |
| B9 |
44 x 62 |
| B10 |
31 x 44 |
C Series, General Stationery: The C Series comes midway between the corresponding A and B series. It is ideal for mailers, postcards and envelopes. For example, C4 envelopes are designed to accommodate A4 letterheads or leaflets. View Sizes
| Name |
Envelope size (mm) |
| C0 |
917 x 1297 |
| C1 |
648 x 917 |
| C2 |
458 x 648 |
| C3 |
324 x 458 |
| C4 |
229 x 324 |
| C5 |
162 x 250 |
| C6 |
114 x 162 |
| C7 |
81 x 114 |
| C8 |
57 x 81 |
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