One extra fold changes the format
Moving from C5 to C6 usually means reducing the finished insert from A5 to A6. For A4, that changes one fold into two and doubles the number of paper layers again.
Envelope comparison
C5 vs C6 envelope
C5 is 162 × 229 mm and commonly takes A5 flat or A4 folded once. C6 is 114 × 162 mm and commonly takes A6 flat or A4 folded twice.
Nominal size reference
Compare the recorded formats
Every table uses nominal exterior width × height. International sizes lead with millimetres; US sizes lead with conventional fractional inches.
| Format | Native size (width × height) | Converted size (width × height) | Source checked | Context |
|---|---|---|---|---|
| C5International | 162 × 229 mm | 6.378 × 9.016 in | Envelope Manufacturers Association ↗27 August 2026 | A5 paper flat |
| C6International | 114 × 162 mm | 4.488 × 6.378 in | Envelope Manufacturers Association ↗27 August 2026 | A6 paper flat |
Original comparison
See the dimensional difference
The outlines use nominal face dimensions from the canonical records. They do not imply identical seams, flaps, usable capacity or manufacturing tolerance.
Choose C5 when the crease matters
C5 uses more envelope area but keeps A5 material flat and A4 to one fold. C6 is more compact, but extra folding may be undesirable for card, photographs, certificates or presentation material.
Nominal hierarchy is not usable capacity
Nominal envelope dimensions describe the exterior format, not guaranteed usable internal space. Seams, lining, stock thickness, multiple pieces and manufacturing tolerances reduce practical room; sample before a bulk order or print run.