C6 Envelope
C-Series Envelopes (ISO 269) · 7 specs
Direct Answer
The C6 envelope is an ISO 269 standard compact postal envelope measuring 114 × 162 mm (4.49 × 6.38 inches). Designed to enclose an A4 sheet folded in half twice (cross-folded in quarters) or an unfolded A6 picture postcard (105 × 148 mm), it is the global standard for personal correspondence, holiday cards, and gift certificates.
Source: ISO 269:1985 (DIN 678) · Last reviewed Aug 28, 2026
Specs
| Width × Height (Metric) | 114 × 162 mm |
| Width × Height (Imperial) | 4.49 × 6.38 in |
| Geometric Mean Origin | Geometric mean of A6 (105×148 mm) and B6 (125×176 mm) |
| Target Paper Pairing | A4 folded into quarters (105 × 148 mm) or flat unfolded A6 cards/postcards |
| Paper Insertion Clearance | +9 mm width / +14 mm height clearance |
| Weight of Empty Envelope | ~4.0 to 5.5 grams |
| Primary Applications | Personal handwritten letters, greeting cards, holiday cards, RSVP response cards |
Quarter-Fold Letter Standard
C6 (114 × 162 mm) is the classic personal correspondence envelope. By folding an A4 letter in half top-to-bottom and then in half left-to-right, the document forms an exact A6 rectangle (105 × 148 mm) that drops into a C6 envelope with generous clearance.