A4 paper format / International standard paper sizes (2025)
5 hours ago
- ISO 216 defines paper sizes with a height-to-width ratio of √2 (1.4142:1), allowing pages to be cut or combined while maintaining the same aspect ratio.
- The system includes A, B, and C series, with areas based on metric units: A0 has 1 m² area, and each subsequent size halves the area.
- The √2 aspect ratio simplifies copying and magnification (e.g., A3→A4 at 71% reduction) without wasted margins or cut-off text.
- ISO 216 is an international standard adopted by most countries except the US, Canada, and parts of Mexico, where non-standard sizes like Letter and Legal remain common.
- The US Letter format (216×279 mm) has inconsistent aspect ratios, making magnification or reduction between sizes impractical.
- Standardized paper sizes save costs and improve efficiency in offices, printing, and document exchange globally.
- Historical development includes early proposals by Georg Christoph Lichtenberg and formalization by Walter Porstmann in Germany (DIN 476, 1922).
- The system also covers envelope formats (C series), raw paper (RA/SRA), and filing standards (ISO 838 with two-hole system).