The purpose of this site is to explain current international standard paper sizes, covered by the ISO 216 Standard, and to provide size charts to allow a quick lookup of sizes.
ISO Paper Sizes Standard Overview & Rationale
The ISO paper size A standard is based on each size being half of the size of the previous one, when folded parallel to the shorter lengths. This system allows for a variety of useful applications, such as the enlarging and reducing of images without any cutoff or margins, or folding to make a booklet of the next size down.
The mathematics behind this useful feature is that the sheets have an aspect ratio (that’s the ratio of the length to the width) of the square root of 2.
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