Folds and layers
What may fit after a named fold
A4 folded once produces an A5-sized rectangle. The extra layer and fold edge can need more room than a single flat A5 sheet.
- A4 folded once to A5
International · Common internationally
C5 envelope size
162 × 229 mm · converted: 6.378 × 9.016 in
C5 is a common international-market envelope between C4 and C6. It is widely used for A5 paper and once-folded A4 without claiming that withdrawn ISO 269 remains current.
- Native dimensions
- 162 × 229 mm
- Converted display
- 6.378 × 9.016 in
- Opening
- open side
- Aliases
- C5 envelope
What commonly fits flat
Start with the finished insert
A5 paper at 148 × 210 mm leaves a nominal total difference of 14 mm in width and 19 mm in height before construction and chosen clearance.
- A5 paper flat
- A4 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 C5
Choose C5 for A5 flat or A4 with one fold. Choose C6 only when another fold and a smaller finished piece are acceptable.
Nearest useful alternative
C5 compared with C6
C6 is 48 mm narrower and 67 mm shorter, trading presentation space for compactness.
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 ISO 269:1985, the former correspondence-envelope standard, was withdrawn on 27 April 2009.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.