what is letter size paper

Letter size paper 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). Letter size paper is the norm for US federal forms since the early 1980s). The aspect ratio of letter size paper is 22/17 ≈ 1.294, and the diagonal is √8.52 + 112 ≈ 13.901 inches (353.1 mm) in length).