what is letter size

Letter size is a paper size standard defined by the American National Standards Institute (ANSI) and is commonly used as home or office stationery in the United States, Canada, Chile, Colombia, Costa Rica, Mexico, Panama, Guatemala, the Dominican Republic, and the Philippines). It measures 8.5 by 11 inches (215.9 by 279.4 mm) and is similar in use to the A4 paper standard at 210 mm × 297 mm (8.27 in × 11.7 in) used by most other countries, defined in ISO 216 by the International Organization for Standardization). The Reagan administration made Letter-size paper the norm for US federal forms in the early 1980s; previously, the smaller "official" Government Letter size, 8 by 10.5 inches (203.2 by 266.7 mm), was used in government, while 8.5-by-11-inch (215.9 by 279.4 mm) paper was standard in most other offices). The aspect ratio of Letter size is 22/17 ≈ 1.294, and the diagonal is √8.52 + 112 ≈ 13.901 inches (353.1 mm) in length).