Letter or US Letter is a paper size commonly used as home or office stationery in Canada, the United States of America, and Mexico. It measures 8.5 by 11 inches (215.9 mm x 279.4 mm). US Letter size paper is a standard defined by the American National Standards Institute (ANSI), in contrast to the A4 paper used in the rest of the world, which is defined by the International Organization for Standardization (specifically, in ISO 216).