Letter

The Letter paper size is the most ubiquitous standard size used in the United States, Canada, Mexico, and parts of South America. It measures 8.5 inches wide by 11 inches tall, giving it a width-to-height aspect ratio of 1.29:1 and a surface area of 93.5 square inches. Letter originated from early American manual papermaking practices in which its length of 11 inches was about a quarter of the maximum stretch of a vatman's arms. It was later adopted as the standard business letter format by typewriter manufacturers.

Today, Letter is not only used for business letters but is the prevalent size for documents, stationery, notebooks, forms and other personal and commercial printing applications in North America. It is sometimes referred to as American Quarto since its dimensions approximate a quarter size of the historical Demy paper. In 1996, ANSI standardized Letter as the ANSI A size and base for its technical drawing paper series. The ubiquitous Letter dimensions have also led to its adoption for many international uses beyond North America.