Letter (paper size)
Letter or US Letter is a paper size for office use. It is the most common type in Canada, United States, and Mexico. It measures 8.5 by 11 inches (215.9 mm x 279.4 mm). US Letter size is a recognized standard adopted by the American National Standards Institute (ANSI) whereas the A4 is the International Standard (ISO) used in most countries.
In the U.S., paper density is usually measured in "pounds per ream" (of 500 sheets). Typical letter paper has a basis weight of 20 or 24 pounds (9 or 11 kg) – the weight of 500 sheets (a ream) of 17-by-22-inch (432 by 559 mm) paper at 70° F (21.11°C) and at 50% humidity. One ream of 20-pound letter-sized paper weighs 5 pounds, and a single letter-sized sheet of 20-pound paper weighs 0.16 ounces (4.5 g), which is equivalent to 72 g/m2. The most common density of A4 paper is 80 g/m2.
The precise origins of the dimensions of US letter size paper (8.5 × 11 in) 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 8 to 9 inches wide and 10 to 11 inches high, and it is indeed almost exactly one quarter of the old Imperial (British) paper size known as Demy 4to (17½"×22½"), allowing ½" for trimming.
The related paper size known as half letter, statement, or organizer L is exactly one half of the US letter size (8.5 × 5.5 in).
- American Forest and Paper Association. "Why is the standard paper size in the U.S. 8 ½" x 11"?". Retrieved 2014-02-20.
- Blocksma, Mary. Reading the Numbers. New York: Penguin Books, 1989.
- Fyffe, Charles (1969). Basic Copyfitting. London: Studio Vista. p. 74. ISBN 0-289-79705-5.
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