A6
A-Series (ISO 216) · 7 specs
Direct Answer
A6 is an ISO 216 standard paper size measuring 105 × 148 mm (4.13 × 5.83 inches), with a surface area of 1/64 square meter. Created by folding an A4 sheet into quarters, it is the worldwide postal standard for international picture postcards, pocket diaries, and point-of-sale receipt slips.
Source: ISO 216:2007 / Universal Postal Union (UPU) Standards · Last reviewed Aug 28, 2026
Specs
| Width × Height (Metric) | 105 × 148 mm |
| Width × Height (Imperial) | 4.13 × 5.83 in |
| Nominal Surface Area | 0.015625 m² (1/64 m² — 15,625 mm²) |
| Exact Aspect Ratio | 1 : √2 (1 : 1.4142) |
| Weight of Standard 80 gsm Sheet | 1.25 grams |
| Matching Postal Envelope | C6 Envelope (114 × 162 mm) |
| Primary Applications | International postcards, pocket notebooks (Field Notes style), thermal photo prints, lab sample tags |
International Postcard Standard
The Universal Postal Union (UPU) recognizes A6 (105 × 148 mm) as the global standard size for tourist picture postcards. Printed on heavy 250 gsm to 350 gsm postcard board, it mails without an envelope at standard national postcard tariff rates.
Quarter-Fold A4 Utility
Because folding an A4 sheet in half twice produces an exact A6 page, organizations frequently distribute pocket emergency cards, map summaries, and user quick-start guides printed on single A4 sheets pre-creased to A6.