C Series Envelopes – C envelope size chart C0, C1, C2, C3, C4, C5, C6, C7, C8
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Popular Envelope Sizes and Printing Formats with C Series Envelopes
The C series is used only for envelopes and is defined in ISO 269. The area of C series sheets is the geometric mean of the areas of the A and B series sheets of the same number; for instance, the area of a C4 sheet is the geometric mean of the areas of an A4 sheet and a B4 sheet. This means that C4 is slightly larger than A4, and B4 slightly larger than C4. The practical usage of this is that a letter written on A4 paper fits inside a C4 envelope, and a C4 envelope fits inside a B4 envelope.
The C series formats are geometric means between the B series and A series formats with the same number, (e.g., C2 is the geometric mean between B2 and A2). The C series formats are used mainly for envelopes. An A4 page will fit into a C4 envelope. C series envelopes follow the same ratio principle as the A series pages. For example, if an A4 page is folded in half so that it is A5 in size, it will fit into a C5 envelope (which will be the same size as a C4 envelope folded in half).
A, B, and C paper fit together as part of a geometric progression, with ratio of successive side lengths of 21/8, though there is no size half-way between Bn and An-1: A4, C4, B4, “D4″, A3, …; there is such a D-series in the Swedish extensions to the system.
The exact millimetre measurement of the long side of Cn is given by 1000/(2(4n-3)/8)+0.2.
ISO C envelope sizes in millimetres and in inches
|Size||mm × mm||in × in (inches)|
|C0||917 × 1297||36.1 × 51.1|
|C1||648 × 917||25.5 × 36.1|
|C2||458 × 648||18.0 × 25.5|
|C3||324 × 458||12.8 × 18.0|
|C4||229 × 324||9.0 × 12.8|
|C5||162 × 229||6.4 × 9.0|
|C6||114 × 162||4.5 × 6.4|
|C7||81 × 114||3.2 × 4.5|
|C8||57 × 81||2.2 × 3.2|
|C9||40 × 57||1.6 × 2.2|
|C10||28 × 40||1.1 × 1.6|