A-Series (ISO 216)

A0 is the base unit of the ISO 216 international paper standard, defined with an exact surface area of 1 square meter (1.000 m²) and dimensions of 841 × 1189 mm (33.1 × 46.8 inches). Operating on the 1:√2 Lichtenberg aspect ratio, it is the global standard for large architectural CAD plots, engineering schematics, and academic conference poster presentations.

A1 is an ISO 216 standard paper size measuring 594 × 841 mm (23.4 × 33.1 inches), with an exact surface area of 0.500 square meters (half of A0). It is the premier standard format for architectural blueprints, structural engineering drawings, municipal planning maps, and large-format flipcharts.

A10 is the smallest standardized paper size defined under ISO 216, measuring 26 × 37 mm (1.02 × 1.46 inches) with a surface area of 1/1024 square meter. It is standard for admission raffle ticket stubs, micro coupons, small security inspection stamps, and dental sample labels.

A2 is an ISO 216 standard paper size measuring 420 × 594 mm (16.5 × 23.4 inches), with a surface area of 0.250 square meters (one quarter of A0). Providing a balanced medium-large format, it is standard for fine-art photographic prints, architectural site overviews, large wall calendars, and retail window display posters.

A3 is an ISO 216 standard paper size measuring 297 × 420 mm (11.7 × 16.5 inches), with a surface area of 0.125 square meters (one eighth of A0). It is the standard large-format paper supported by commercial office multifunction printers (MFPs), widely used for financial spreadsheets, two-page A4 magazine spreads, and engineering diagrams.

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.

A5 is an ISO 216 standard paper size measuring 148 × 210 mm (5.83 × 8.27 inches), created by cutting or folding an A4 sheet in half. It is the dominant global format for commercial spiral notebooks, daily planners, paperback novels, corporate marketing flyers, and restaurant menus.

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.

A7 is an ISO 216 standard paper size measuring 74 × 105 mm (2.91 × 4.13 inches), with a surface area of 1/128 square meter. Created by cutting an A6 sheet in half, it is widely utilized for pocket memo pads, medical prescription slips, event tickets, and promotional product tags.

A8 is an ISO 216 standard paper size measuring 52 × 74 mm (2.05 × 2.91 inches), with a surface area of 1/256 square meter. Approximately matching the footprint of standard bank payment cards, it is standard for European business cards, loyalty stamps, retail price tags, and transit ticket stubs.

A9 is an ISO 216 standard paper size measuring 37 × 52 mm (1.46 × 2.05 inches), with a surface area of 1/512 square meter. Created by cutting an A8 sheet in half, it is standard for miniature barcode labels, commemorative postage stamps, bookkeeper index tabs, and food expiration stickers.