C4

The C4 envelope has dimensions of 324mm x 229mm, giving it a surface area of around 74,096 mm2. The maximum enclosure size is typically 224mm x 318mm. The C4 was created based on the ISO 216 standard which assigns each envelope size a number starting at C0. It gets its name specifically from being able to hold a standard A4 sheet of paper which measures 210mm x 297mm. The C4 envelope can accommodate an A4 sheet, invitation, magazine or catalog when folded once. Compared to C5 envelopes, the C4 offers significantly more area while still being easy to mail. It provides a versatile mid-size option between postcards and large packages. The C4 is widely used for commercial mailings and is one of the most common business and catalog envelope sizes globally along with DL and C5.