Indeed, even if a number of international standards exist about paper sizes, various sizes are still used daily around the world. There is in fact no universal standard for defining an international format that would be accepted and used by all countries of the world. North America remains the only to use different paper sizes from the rest of the world (Japan also have local specifications on B size). So that this feature is not a handicap in trade with other countries, there are standards that are integrated to all machines for printing and conversion or paper transfer (fax, printers ...) from their conception.
The most common format mainly used in Europe, Africa, Asia, Oceania and South America, is A4. The latter is derived from the ISO, and more specifically ISO 216, created in 1975 on the basis of DIN 476 (Deutsches Institut für Normung, german norms Institute), filed in 1922.
But it is a letter dated 25 October 1786, addressed by Physics Professor Lichtenberg to his friend Beckmann, that is the oldest evidence of a paper taking aheight-to-widht ratio. This proportion was for the first time based on the square root of 2, that is to say that the length of the sheet was equal to its width x 1.4142 (a / b = 2 b / a = √ 2).
In this letter to his colleague, Lichtenberg explained all the benefits of the square root of 2 as the proportion between the length and width of the paper. We can therefore say that Lichtenberg is the father of A in the standard paper sizes.
At its enactment of its “Loi du timbre” (stamp law) of 1798, the French also brought help by introducing paper sizes (Large register, Grand Paper, Paper Middle, Small Paper, Half Sheet, Commercial Paper) that for most adopted √ 2 ratio (length / width). But all did not use the same ratio, which is why these formats were quickly forgotten.
It is the German Walter Portsmann who studied Lichtenberg ratio for proposing to the German DIN in 1918. The idea was to provide a universal paper size that could replace many formats still used yet. Space saving and easy storage convinced DIN to adopt this standard in 1922, followed by many countries (42 between 1924 and 1975). This standard became international in 1975.
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