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International Styles & Standards

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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