Letter (paper size)


Letter or ANSI Letter is a paper size commonly used as home or office stationery in the United States, Canada, Chile, Colombia, Costa Rica, Mexico, Panama, the Dominican Republic and the Philippines. It measures. US Letter-size paper is a standard defined by the American National Standards Institute, in contrast to A4 paper used by most other countries, and adopted at varying dates, which is defined by the International Organization for Standardization, specifically in ISO 216.

Details

The Reagan administration made Letter-size paper the norm for U.S. federal forms in the early 1980s; previously, the smaller "official" Government Letter size, , was used in government, while paper was standard in most other offices. The aspect ratio is ≈1.294 and the diagonal is ≈13.901 in length.
In the U.S., paper density is usually measured in "pounds per ream". Typical Letter paper has a basis weight of paper of – the weight of 500 sheets of paper at and at 50% humidity. One ream of 20-pound Letter-sized paper weighs, and a single Letter-sized sheet of 20-pound paper weighs, which is equivalent to 75.19 g/m2. Some metric information is typically included on American ream packaging. For example, 20-pound paper is also labeled as 75 g/m2. The most common density of A4 paper is 80 g/m2.
The precise origins of the dimensions of US letter-size paper are not known. The American Forest & Paper Association says that the standard US dimensions have their origin in the days of manual paper making, the 11" length of the standard paper being about a quarter of "the average maximum stretch of an experienced vatman's arms". The letter size falls within the range of the historical quarto size, which since pre-modern times refers to page sizes of wide and high, and it is indeed almost exactly one quarter of the old Imperial paper size known as Demy 4to - - allowing a for trimming.
The related paper size known as half letter, statement, or organizer L is exactly one half of the US Letter size: .