Half the last

The A series

Start with a sheet of one square metre whose sides stand in the ratio 1 to √2. That is A0, 841 × 1189 mm. Cut it across the long side and you have two A1. Keep going.

A0 to A10

A series, millimetres, width × height. Bars show height to scale.
SizemmTypical use
A0841 × 1189Technical drawings, posters
A1594 × 841Technical drawings, posters, flip charts
A2420 × 594Flip charts; drawings, diagrams, large tables
A3297 × 420Drawings, diagrams, large tables; newspapers
A4210 × 297Letters, magazines, forms, catalogues, printer and copier output
A5148 × 210Note pads, books
A6105 × 148Postcards, books
A774 × 105
A852 × 74Playing cards
A937 × 52
A1026 × 37
How exact is an A4 sheet?

ISO 216 allows ±1.5 mm on dimensions up to 150 mm, ±2 mm from 150 to 600 mm, and ±3 mm above that. The older German standard, DIN 476, was stricter: ±1, ±1.5 and ±2 mm for the same ranges.1

The B series → The C series → ← Why √2