The shaku (尺), or Japanese foot, is a unit of length derived from the Chinese chi, which was based upon the length of the forearm (like a cubit). The shaku has been standardized as 10/33 meters (30.3 centimeters or 11.9 inches) since 1981. This means that there are 3.3 shaku to one meter.
Just as with the Chinese chi, the shaku is divided into ten smaller units, known as sun (寸). In Kendo , shaku are used to measure the length of shinai and men himo. Together, ten shaku form a larger unit known in Japanese as a jō (丈). The Japanese also had a third derived unit, the ken, equal to 6 shaku. This unit was used extensively in traditional Japanese architecture as the distance between supporting pillars in Buddhist temples and Shinto shrines.
Etymologically, shaku entered English in the early 18th century, deriving from the Japanese pronunciation of the kanji 尺. Traditionally, the measurement varied over time, location, and use. By the early 19th century they were largely within the range of 0.30175 to 0.303 meters (11.880 in to 11.929 in), but a longer value of the shaku (also known as the kōrai-shaku) was 1.17 times longer than the present value (35.5 centimeters or 14.0 inches). The use of the unit for official purposes was banned on March 31, 1966. Other uses of the shaku include traditional Japanese carpentry and some other fields. The traditional Japanese bamboo flute known as the shakuhachi ("shaku and eight") derives its name from its length of one shaku and eight sun. Similarly, the koku remains in use in the Japanese lumber trade (ten cubic shaku comprised a koku, reckoned as the amount of rice necessary to sustain a peasant for a year)