A6 is the smallest size in the A Series of paper. The ISO 216 standard defines A6 size to be 105mm × 148mm, which is also exactly a quarter the size of an A4. A6 is also the worldwide standard size of a postcard.
Usually A6 sized paper will be used for postcards, booklet printing, flyers, leaflets, advertisements, or if on heavier stock, it can be scored and folded to make A6 sized greeting cards.
In the ISO paper size system, the height-to-width ratio of all pages is the square root of two. In other words, the width and the height of a page relate to each other like the side and the diagonal of a square. This aspect ratio is especially convenient for a paper size. If you put two such pages next to each other, or equivalently cut one parallel to its shorter side into two equal pieces, then the resulting page will have again the same width/height ratio.
- A6 is a quarter the size of A4, and half the size of A5.
- A6 is one-eighth the size of A3, and one-sixteenth the size of A2.
- Thirty-two A6 will make up an A1, and sixty-four to make up an A0.