Envelope reference · ISO C family
C6 envelope size
A compact envelope sized for A6 cards or an A4 sheet folded twice, often used for invitations, personal notes, and small direct-mail pieces.
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C6 dimensions and paper fit
In landscape orientation, C6 measures 114 × 162 mm, or 4.49 × 6.38 inches. A6 at 105 × 148 mm flat, or A4 folded twice to A6.
| Unit | Width | Height |
|---|---|---|
| Millimeters | 114 mm | 162 mm |
| Centimeters | 11.4 cm | 16.2 cm |
| Inches | 4.49 in | 6.38 in |
| Pixels at 300 DPI | 1346 px | 1913 px |
Insert & folding
What fits inside C6?
A6 at 105 × 148 mm flat, or A4 folded twice to A6. Fold A4 to A5, then fold once more to A6. Allow for the thickness created by multiple sheets.
Comparison
How C6 differs from nearby envelopes
C6 is 9 mm wider and 14 mm taller than A6. It is shorter and wider than the long DL envelope.
Works well for
Common C6 uses
- A6 invitations
- Greeting cards
- Personal notes
- Compact mail pieces
Check before using
Where it can go wrong
- A5 inserts
- US A2 invitation-envelope templates
- Mailing without checking minimum dimensions
Postal note
Dimensions do not determine postage by themselves.
Small envelopes can still have minimum-size rules. Confirm eligibility with the postal service before producing a large run.
Historical measurement source
Based on the C-series envelope convention.
The official ISO page identifies ISO 269:1985 as withdrawn. Paper Size Lab cites it as the historical designation source, not as a current postal requirement.
View ISO 269:1985 statusQuestions people ask
C6 envelope FAQ
What size is a C6 envelope?
C6 measures 114 × 162 mm, or 4.49 × 6.38 inches.
What paper fits in a C6 envelope?
A6 at 105 × 148 mm flat, or A4 folded twice to A6.
How should paper be folded for a C6 envelope?
Fold A4 to A5, then fold once more to A6. Allow for the thickness created by multiple sheets.
Does a C6 envelope qualify for standard postage?
Small envelopes can still have minimum-size rules. Confirm eligibility with the postal service before producing a large run.