A4
A-Series (ISO 216) · 7 specs
Direct Answer
A4 is the international standard paper format defined by ISO 216, measuring 210 × 297 mm (8.27 × 11.69 inches). Utilized by over 140 countries representing approximately 95% of the world's population, it is the universal standard for business letters, official contracts, academic papers, magazine publishing, and desktop office printers.
Source: ISO 216:2007 / DIN 476-1 / BS 4000 · Last reviewed Aug 28, 2026
Specs
| Width × Height (Metric) | 210 × 297 mm |
| Width × Height (Imperial) | 8.27 × 11.69 in |
| Nominal Surface Area | 0.0625 m² (1/16 m² — 62,500 mm²) |
| Exact Aspect Ratio | 1 : √2 (1 : 1.4142) |
| Weight of Standard 80 gsm Sheet | 5.0 grams exactly |
| Weight of 500-Sheet Ream (80 gsm) | 2.50 kg (5.51 lbs) |
| Postal Envelope Pairings | C4 (unfolded), C5 (folded once), C6 (folded twice), DL (folded in thirds) |
Global Standard Letter Format
Except for the United States, Canada, and parts of Mexico (which use US Letter), A4 is the legally mandated paper standard for all governmental treaties, corporate correspondence, university theses, medical files, and judicial court filings worldwide.
Postal Calculations and Ream Weights
Because an A4 sheet has a surface area of exactly 1/16 m², one standard 80 gsm sheet weighs exactly 5.0 grams. This simplifies international postal calculations: a standard 20g airmail limit allows exactly 3 sheets of A4 paper (15g) plus a standard 5g DL or C6 envelope without exceeding postage thresholds.