Printernational - Information about print design

ISO Envelope sizes

International standard ISO (International Organization for Standardization) 269 defines several standard envelope sizes, which are designed for use with ISO 216 standard paper sizes (the A series). The German standard DIN 678 defines a similar list of envelope formats.

This envelope series was designed to accommodate ISO A size papers. Metric measurements are the finished envelope size. Inch measurements are approximate (calculated at 25.4 mm = 1 inch and rounded off).

ISO Envelope Sizes

Name Size in millimeters Size in inches Usage and comments
C0 917 mm x 1297 mm 36.12 in x 51.6 in For flat A0 sheet.
C1 648 mm x 917 mm 25.50 in x 36.12 in For flat A1 sheet.
C2 458 mm x 648 mm 18 in x 25.50 in For flat A2 sheet, A1 folded in half.
C3 324 mm x 458 mm 12.75 in x 18 in For flat A3 sheet, A2 folded in half.
C4 229 mm x 324 mm 9 in x 12.75 in For flat A4 sheet, A3 folded in half. Common.
C5 162 mm x 229 mm 6.38 in x 9 in For flat A5 sheet, A4 folded in half. Common.
C6 114 mm x 162 mm 4.5 in x 6.38 in For A5 folded in half. Common.
C7/6 81 mm x 162 mm 3.19 in x 6.38 in For A5 sheet folded in thirds. Uncommon.
C7 81 mm x 114 mm 3.19 in x 4.5 in For A5 folded in quarters. Uncommon.
DL 110 mm x 220 mm 4.32 in x 8.69 in For A4 sheet folded in thirds, A5 in half. Common.

Although DL is not part of the ISO C series, it is a very widely used standard size. DL, probably at one time the abbreviation of DIN Lang (Deutsche Industrie Norm, Long), is now identified as "Dimension Lengthwise" by ISO 269.