C3

The C3 envelope has dimensions of 458mm x 324mm giving it a surface area of approximately 148,592 mm2. Its maximum enclosure size is slightly smaller than its exterior dimensions, typically around 318mm x 450mm. The C3 envelope is not very commonly used compared to smaller envelope sizes. It gets its name from the ISO 216 standard which assigns each envelope size a number starting at C0. The C3 was created to hold a standard A3 sheet of paper which measures 297mm x 420mm. While not as ubiquitous as C4 or C5 envelopes, the sizable C3 can be useful for holding large documents, drawings, posters or other oversized sheet materials needing to be mailed. It provides significantly more area than a standard business envelope.