C4 Envelope Size
C4 measures 229 × 324 mm (9.02 × 12.76 in). The C series is used for envelopes.
| Millimetres | 229 × 324 mm |
|---|---|
| Centimetres | 22.9 × 32.4 cm |
| Inches | 9.02 × 12.76 in |
| Aspect ratio (long ÷ short) | 1.415 |
| Series | ISO 269 C series (envelopes) |
| Fits | An A4 sheet laid flat fits inside a C4 envelope |
| Fits inside | A C4 envelope fits inside a B4 envelope |
Where you will see C4
C4 is the envelope that holds a flat A4 sheet without folding, so it is the standard choice for sending documents unfolded.
How C4 relates to A and B sizes
In the ISO 269 C series, each C size is slightly larger than the A size with the same number (210 × 297 mm for A4), so a flat A4 sheet fits inside a C4 envelope. The C4 envelope in turn fits inside a B4 envelope (250 × 353 mm).
Frequently asked questions
What size is a C4 envelope?
A C4 envelope is 229 × 324 mm (9.02 × 12.76 inches).
What fits in a C4 envelope?
A flat A4 sheet (210 × 297 mm) fits in a C4 envelope with a small margin of 19 mm in width and 27 mm in height.
Related
- C3 Envelope Size324 × 458 mm
- C5 Envelope Size162 × 229 mm
- A4 Paper Size210 × 297 mm
- B4 Paper Size250 × 353 mm
Last updated: 2026-10-03