International Envelope Paper Sizes

International Envelope Size in cm, inches

The standard envelope sizes are defined by the international standard ISO 269. They are generally designed to be used with paper sizes that follow the ISO 216 standard. The most commonly used envelope sizes are from the C series. An A4 piece of paper will fit into a C4 envelope. The DL envelope has a different aspect ratio to the C series, which is why it does not appear in that series. The DL envelope is the most common envelope used in business. DL is short for 'Dimension Lengthwise', however it was previously known as DIN Lang in Germany where it originated in the 1920s. An A4 sheet of paper folded three times, parallel to its smaller sides, will fit into a DL envelope.

Size Millimeters Inches
DL size 220 x 110 mm 8.7 x 4.3 in
B4 size 353 x 250 mm 13.9 x 9.8 in
B5 size 250 x 176 mm 9.8 x 6.9 in
B6 size 176 x 125 mm 6.9 x 4.9 in
C3 size 458 x 324 mm 18 x 12.8 in
C4 size 324 x 229 mm 12.8 x 9 in
C5 size 229 x 162 mm 9 x 6.4 in
C6/C5 size 229 x 114 mm 9 x 4.5 in
C6 size 162 x 114 mm 6.4 x 4.5 in
C7/C6 size 162 x 81 mm 6.4 x 3.2 in
C7 size 114 x 81 mm 4.5 x 3.2 in
E4 size 400 x 280 mm 15.7 x 11 in