Paper Size Standards Explained
The ISO 216 A-series is the international standard for paper sizes used in most of the world. Starting from A0 (841×1189mm), each step halves the longer dimension: A1, A2, A3, A4, and so on. A4 (210×297mm / 8.27×11.69 in) is the everyday office standard outside North America.
The ISO B-series provides intermediate sizes between consecutive A sizes. B0 is 1000×1414mm, and each step halves down to B6. B-series is used for posters, notebooks, and envelopes. Note: the JIS B-series used in Japan differs slightly from ISO B.
North American sizes — Letter (8.5×11 in), Legal (8.5×14 in), and Tabloid (11×17 in) — are defined by ANSI and remain the default in the US and Canada. Letter is wider but shorter than A4, which can cause margin misalignment when mixing document standards.
Frequently Asked Questions
A4 is 210mm × 297mm (21cm × 29.7cm, 8.27 × 11.69 inches). It is the ISO 216 standard and the most common office paper size worldwide.
A-series starts at A0 and halves each time. B-series provides intermediate sizes. B-series is used for notebooks, posters, and envelopes.
US Letter (216×279mm / 8.5×11 in) is slightly wider but shorter than A4. Mixing these standards can cause margin issues when printing.