papersize

Paper size refers to the dimensions of a sheet of paper, standardized to enable predictable use in writing, printing, and drawing. Standards ensure compatibility among printers, folders, binders, and production workflows across regions and industries.

The ISO 216 standard defines the A-series and B-series of paper sizes. The A-series uses a sqrt(2) aspect ratio, with A0 as the base size of 841 by 1189 mm and an area of 1 square meter; each step down halves the area, yielding sizes such as A1, A2, and so on. The most common size is A4 (210 × 297 mm), widely used for letters, reports, and printers. The B-series shares the same aspect ratio and is often used for posters, diagrams, and applications where a different scale is desired. ISO 216 was standardized in 1975, building on earlier standards such as DIN 476.

North America uses a different set of sizes, including Letter (8.5 × 11 inches), Legal (8.5 × 14 inches), and Ledger/Tabloid (11 × 17 inches). These sizes do not follow the ISO sqrt(2) system and remain prevalent in business, education, and consumer printing in the United States and Canada. In Japan and parts of Asia, JIS sizes are common, with overlaps to the A- and B-series but with regional conventions for publishing and administration.

In digital contexts, paper size appears in page layout, print dialogs, and document metadata. CSS for print and PDF metadata specify the target page size to ensure consistent rendering across devices. The concept originated in early 20th-century standardization and remains essential for interoperability in both physical and digital printing.