Foolscap paper has different dimensions than A4 with foolscap measuring 8.5 inches by 13.5 inches, and A4 measuring 8.25 inches by 11.75 inches. A4 paper is used in most countries; however, in the United States, letter-size paper is more common and this measures 8.5 inches by 11 inches.
A4 is a standardized size of paper used by the International Standards Organization. However, before the introduction of A4, foolscap was the standard size in the British Commonwealth and Europe. Foolscap gets its name from a "fool's cap" worn by jesters during the Middle Ages. Foolscap paper was originally watermarked with the image of a fool's cap and bells.