Folds and layers
What may fit after a named fold
A5 folded once or A4 folded twice produces an A6-sized outer rectangle. Each additional fold increases layers and practical resistance.
- A5 folded once to A6
- A4 folded twice to A6
International · Common internationally
C6 envelope size
114 × 162 mm · converted: 4.488 × 6.378 in
C6 is the familiar international-market envelope for ISO A6 paper. It must not be confused with the larger US A6 announcement envelope.
- Native dimensions
- 114 × 162 mm
- Converted display
- 4.488 × 6.378 in
- Opening
- open side
- Aliases
- C6 envelope
What commonly fits flat
Start with the finished insert
ISO A6 paper at 105 × 148 mm leaves a nominal total difference of 9 mm in width and 14 mm in height before seams, lining and clearance.
- A6 paper flat
- A5 paper folded once
- A4 paper folded twice
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 C6
Choose C6 for a compact A6 piece or folded A-series correspondence. Choose C5 when A5 should remain flat or A4 should have only one fold.
Nearest useful alternative
C6 compared with A6 announcement
US A6 announcement is wider and slightly taller; the shared A6 label does not make the formats equivalent.
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 ISO 269:1985, the former correspondence-envelope standard, was withdrawn on 27 April 2009.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.