C5

The C5 envelope has dimensions of 229mm x 162mm, giving it a surface area of 37,098 mm2. The maximum enclosure size is typically around 156mm x 223mm. The C5 was created based on the ISO 216 standard which assigns each envelope a number starting at C0. It gets its C5 designation specifically from being able to hold an A4 sheet of paper folded in half widthwise - an A4 sheet measures 210mm x 297mm. When folded in half it becomes an A5 sheet at 148mm x 210mm which fits neatly into a C5 envelope. The versatile C5 size is widely used for both commercial and personal mail. It provides a good balance of space and portability. C5 envelopes are commonly used for letters, brochures, invoices and other flat mailings. Along with DL and C6 sizes, the C5 envelope remains one of the most ubiquitous envelope sizes globally.