Paper[Paper?:paper sample maker cutting machine] sizes were standardized in Germany in 1922, and adopted throughout Europe in 1930, via Standard 216 of the International Standards Organization (ISO).
The ISO is a non-governmental entity that publishes international standards. Standard 216 was most recently updated in 2007, adding standards to define which direction of the paper is parallel to the machine, which can affect paper curl. The North American paper standards were far more informally adopted in the late 19th century. Exact origins of the letter-sized paper are argued by historians, but may be based on the size and weight of foolscap paper, which was commonly used at the time. Foolscap typically measured 16.75 inches by 13.5 inches (about 42.5 cm by 34 cm). Some argue the North American standard letter size came from cutting the foolscap in half.
