Who uses paper sizes A4, A5,A6 ect....?

Answer 1

The ISO standard paper size system covers a wide range of formats, but not all of them are widely used in practice. Among all formats, A4 is clearly the most important one for daily office use. Some main applications of the most popular formats can be summarized as:

A4: letters, magazines, forms, catalogs, laser printer and copying machine output
A5: note pads
A6: postcards
More information at the site below:

Answer 2

Paper Sizes A4 A5 A6

Answer 3

I use A4.

All of Europe, and apparently most of the rest of the world. I read that only the US, Canada, I think the Philippines and maybe one other place uses "letter size".

A4 is a bit longer and narrower than letter-size. A5 is as long as A4 is wide, and half as wide as A4 is long--and so on. And they all have the same proportions. It's cool in a way but I miss 8 1/2 x 11.

Answer 4

The ISO paper sizes are based on the metric system. The square-root-of-two ratio does not permit both the height and width of the pages to be nicely rounded metric lengths. Therefore, the area of the pages has been defined to have round metric values. As paper is usually specified in g/m², this simplifies calculation of the mass of a document if the format and number of pages are known. ISO 216 defines the A series of paper sizes based on these simple principles: The height divided by the width of all formats is the square root of two (1.4142). Format A0 has an area of one square meter. Format A1 is A0 cut into two equal pieces. In other words, the height of A1 is the width of A0 and the width of A1 is half the height of A0. All smaller A series formats are defined in the same way. If you cut format An parallel to its shorter side into two equal pieces of paper, these will have format A(n+1).