Folds and layers
What may fit after a named fold
A3 folded once to A4 creates the same nominal finished rectangle. Heavy A3 stock becomes two layers, so it deserves more working clearance than one A4 sheet.
- A3 folded once to A4
International · Common internationally
C4 envelope size
229 × 324 mm · converted: 9.016 × 12.756 in
C4 is a large international-market envelope commonly associated with unfolded A4 paper. It is part of the familiar C-series progression, but the former ISO envelope standard ISO 269:1985 is withdrawn.
- Native dimensions
- 229 × 324 mm
- Converted display
- 9.016 × 12.756 in
- Opening
- open side
- Aliases
- C4 envelope
What commonly fits flat
Start with the finished insert
A4 paper at 210 × 297 mm sits within the nominal C4 face with 19 mm total width difference and 27 mm total height difference before seams and tolerances.
- A4 paper flat
- A3 paper folded once
Nominal exterior size ≠ usable interior space
Seams, lining, stock thickness, contents and manufacturing tolerance can reduce practical room. Confirm the manufactured envelope and sample before bulk use.
Decision
When to choose C4
Choose C4 when A4 must remain flat or presentation material should avoid a crease. Choose C5 if one fold is acceptable and compactness is more important.
Nearest useful alternative
C4 compared with C5
C5 is the next smaller familiar format and changes the task from A4 flat to A4 folded once.
The overlay is proportional to the canonical nominal dimensions. It compares the face rectangles only; it does not claim equal construction, internal capacity or postal treatment.
Clearance and tolerance
Why a positive number can still be too tight
Matcher clearance is applied per edge. Its “remaining” value is the total unused width and height after that allowance. A technically passing result with less than 2 mm remaining on either final dimension is labelled borderline and is never ranked as an ordinary recommendation.
Standards and rights note
Common current market convention. ISO 269:1985, the former correspondence-envelope standard, was withdrawn on 27 April 2009.
Minimum factual dimensions independently recorded. No standard or manufacturer wording, table, diagram, photograph, logo or dieline is reproduced.