International Envelope Paper Sizes

DL 220 × 110 mm B4 353 × 250 mm B5 250 × 176 mm B6 176 × 125 mm C3 458 × 324 mm C4 324 × 229 mm C5 229 × 162 mm C6/C5 229 × 114 mm C6 162 × 114 mm C7/C6 162 × 81 mm C7 114 × 81 mm E4 400 × 280 mm

Further Information

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.

Format	Width × Height (mm)	Width × Height (in)
DL	220 × 110 mm	8.7 × 4.3 in
B4	353 × 250 mm	13.9 × 9.8 in
B5	250 × 176 mm	9.8 × 6.9 in
B6	176 × 125 mm	6.9 × 4.9 in
C3	458 × 324 mm	18 × 12.8 in
C4	324 × 229 mm	12.8 × 9 in
C5	229 × 162 mm	9 × 6.4 in
C6/C5	229 × 114 mm	9 × 4.5 in
C6	162 × 114 mm	6.4 × 4.5 in
C7/C6	162 × 81 mm	6.4 × 3.2 in
C7	114 × 81 mm	4.5 × 3.2 in
E4	400 × 280 mm	15.7 × 11 in