The history of the A4 sheet
(or: How the DIN/ISO 216 was thought out)
The DIN/ISO paper format was invented because a logical, standardized way
to determine paper sizes was wanted by the printing industry.
To do this, they started off with a standard size, and decided to call it "A0"
The definition of an A0 sheet was chosen as a piece of paper that was 1m2
large. The second criteria was that the paper had to be easy to handle (in other
words, that it wasn't square). It is believed that the original Height/Width
ratio was chosen to be sqrt(2):1, but in the final definition, a slightly
different ratio was chosen. Professor Pi points out that this ratio is the silver ratio - see his node for more about this!
Ratio used in the ISO : 1.4125
Ratio of sqrt(2):1 : 1.4142
In any case - the largest page size became A0 (1m2)
or 840.901 * 1189.202 mm. From this size, every time the paper size goes smaller
(A1,2,3 etc), the paper size was halved, by splitting the longest side in two.
This (obviously) leads to all the paper sizes in the A series to have the same
H:W ratio, and the difference between any paper size and the one smaller, is
that the smaller one has half the area of the larger size. (see omegas excellent
writeup earlier in this node for a complete table)
-30-
source: something I learnt when I worked in a printshop, logic, and omegas' w/u above this one