A0
A-Series (ISO 216) · 7 specs
Direct Answer
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.
Source: ISO 216:2007 (DIN 476-1) · Last reviewed Aug 28, 2026
Specs
| Width × Height (Metric) | 841 × 1189 mm |
| Width × Height (Imperial) | 33.1 × 46.8 in |
| Nominal Surface Area | 1.000 m² (1,000,000 mm²) |
| Exact Aspect Ratio | 1 : √2 (1 : 1.4142 — Lichtenberg ratio) |
| Weight of Standard 80 gsm Sheet | 80.0 grams exactly |
| Halving Relationship | Cut in half across length yields 2 sheets of A1 |
| Primary Applications | Architectural blueprints, GIS cartography, technical CAD schematics, academic research posters |
The 1 Square Meter Foundation
The entire ISO 216 paper standard is constructed from A0. By defining A0 with a surface area of exactly 1.0 square meter and sides in the ratio 1:√2, calculating paper weight becomes effortless: a single sheet of standard 80 g/m² (gsm) paper in A0 format weighs exactly 80.0 grams.
Lichtenberg Scaling Mathematics
First recorded by German physicist Georg Christoph Lichtenberg in 1786 and standardized in 1922 by Walter Porstmann as DIN 476, the √2:1 aspect ratio allows documents to be photographically enlarged or reduced between any A-series sizes (e.g. from A4 to A0 at 400% zoom) without any cropping, margin distortion, or whitespace waste.