International envelope Sizes / Application examples / Envelope formats / folds and sizes
Application Examples 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:
The main advantage of the ISO standard paper sizes becomes obvious for users of copying machines: Example 1: You are in a library and want to copy an article out of journal that has A4 format. In order to save paper, you want copy two journal pages onto each sheet of A4 xerox paper. If you open the journal, the two A4 pages that you will now see together have A3 format. By setting the magnification factor on the copying machine to 71% (that is sqrt(0.5)), or by pressing the A3A4 button that is available on most copying machines, both A4 pages of the journal article together will fill exactly the A4 page produced by the copying machine. One reproduced A4 page will now have A5 format. No wasted paper margins appear, no experiments for finding the appropriate magnification factor are necessary. The same principle works for books in B5 or A5 format. Copying machines designed for ISO paper sizes usually provide special keys for the following frequently needed magnification factors:
Not only the operation of copying machines in offices and libraries, but also repro photography, microfilming and printing are simplified by the 1:sqrt(2) aspect ration of ISO paper sizes. Example 2: If you prepare a letter, you will have to know the weight of the content in order to determine the postal fee. This can be very conveniently calculated with the ISO A series paper sizes. Usual typewriter and laser weighs 80 g/m x m. An A0 page has an area of 1m x m, and the next smaller A series page has half of this area. Therefore the A4 format has an area of 1/6 m x m and weighs with the common paper quality 5 g per page. If we estimate 20g for a C4 envelope (including some safety margin), then you will be able to put 16 A4 pages into a letter before you reach the 1000g limit for the next higher postal fee. Calculation of the mass of books, newspapers, or packed paper is equally trivial. You probably will not need such calculations often, but they nicely show the beauty of the concept of metric paper sizes. Using standard paper sizes saves money and makes life simpler in many applications. For example, if all scientific journals used only ISO formats, then libraries would have to buy only very few different sizes for the binders. Shelves can be designed such that standard formats will fit in exactly without too much wasted shelf volume. The ISO formats are used for surprisingly many things besides office paper: the German citizen ID card has format A7, both the European Union and the U.S.(!) passport have format B7 and library microfiches have format A6. In some countries (e.g. Germany) even many of toilet paper have format A6.
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