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Simple guide to ISO Paper Formats

This is a simple guide explaining paper formats like the A5, A4 or A3 that makes visualization of different standard paper sizes very simple.

The ISO standard letter format in Europe is known as A4. Put two of them together and you get the larger A3 sheet, or fold one in half and get the smaller A5. Interestingly enough, all of these have exactly the same height to width aspect ratio.

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.

An Width - 2-1/4-n/2 Height - 21/4-n/2

The above is a simple formula to calculate the dimensions of An paper format.

The aspect ratio defining the ISO page sizes is called the Lichtenberg Ratio. It's actually the square root of 2.

The ISO paper size system concept [ via ]