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ISO 216
ISO 216 specifies international standard (ISO) paper sizes used in most countries in the world today. It is the standard which defines the commonly available A4 paper size. The international ISO standard is based on the German DIN standard 476 (DIN 476) from 1922. Some of the formats contained therein were independently invented in France during its revolution, but were later forgotten.[1] The aspect ratio used by this norm was mentioned in a letter by the German Georg Christoph Lichtenberg, written on 25 October 1786.[2]
A series
A size chart illustrating the ISO A series. The most frequently used of this series is the size A4 (210 × 297 mm). A4 paper is 6 mm narrower and 18 mm longer than the "Letter" paper size, 8½ × 11 inches (216 × 279 mm), commonly used in North America. The geometrical rationale behind the square root of 2 is to maintain the aspect ratio of both of the rectangles after cutting the larger rectangle in half. Given a rectangle with a longer side, x, and a shorter side, y, the following equation shows how the aspect ratio of a rectangle compares to that of a half rectangle: \ x/y = y/(x/2) which reduces to x/y = \sqrt{2} or an aspect ratio of 1 : \sqrt{2} The formula that gives the larger border of the paper size An in metres and without rounding off is the geometric sequence: a_n = 2^{1/4 - n/2}. The paper size An thus has the dimension a_n × a_{n+1}. The exact millimetre measurement of the long side of An is given by \left \lfloor 1000/(2^{(2n-1)/4})+0.2 \right \rfloor. B series
A size chart illustrating the ISO B series. There is also an incompatible Japanese B series defined by the JIS. The lengths of JIS B series paper are approximately 1.22 times those of A-series paper. The exact millimetre measurement of the long side of Bn is given by \left \lfloor 1000/(2^{(n-1)/2})+0.2 \right \rfloor. C series
A size chart illustrating the ISO C series. The exact millimetre measurement of the long side of Cn is given by \left \lfloor 1000/(2^{(4n-3)/8})+0.2 \right \rfloor. TolerancesThe tolerances specified in the standard are:
A, B, C comparison
ApplicationBefore the adoption of ISO 216, many different paper formats were used internationally. These formats did not fit into a coherent system and were defined in terms of non-metric units. The ISO 216 formats are organized around the ratio 1:\sqrt{2}; two sheets next to each other together have the same ratio, sideways. This simplifies copying (e.g. two A4 sheets in reduced size onto one A4 sheet; an A4 sheet in magnified size on to a A3 sheet; or a A5 sheet in magnified size on to a A4 sheet). The principal countries not generally using the ISO paper sizes are the United States and Canada, which use the Letter, Legal and Executive system. (Canada uses a P-series of sizes, which are the US paper sizes rounded to metric dimensions.) Rectangular sheets of paper with the ratio 1:\sqrt{2} are popular in paper folding, where they are sometimes called "A4 rectangles" or "silver rectangles".[3] (Confusingly, "silver rectangle" can also refer to a rectangle in the proportion 1:(1+\sqrt{2})), known as the silver ratio.) See alsoExternal links
be-x-old:ISO 216 ca:ISO 216 et:ISO 216 es:ISO 216 fr:ISO 216 gl:ISO 216 ko:ISO 216 it:ISO 216 he:ISO 216 lt:ISO 216 nl:ISO 216 no:ISO 216 pt:ISO 216 ro:ISO 216 ru:ISO 216 sl:ISO 216 sr:DIN 476 fi:ISO 216 sv:A-format th:ISO 216 tr:ISO 216 uk:ISO 216 zh:ISO 216 Source: Wikipedia | The above article is available under the GNU FDL. | Edit this article
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