Shaku (unit)

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Unit system Japanese units
Unit of length
Unit conversions
1 尺 in ...... is equal to ...
   SI units    0.3030 m
   imperial/US units    0.9942 ft
11.93 in

The shaku (Japanese: ) or Japanese foot[1][2] is a Japanese unit of length derived (but varying) from the Chinese chi, originally based upon the distance measured by a human hand from the tip of the thumb to the tip of the forefinger[3] (compare Span). Traditionally, the length varied by location or use, but it is now standardized as 10/33 meters (30.3 centimeters or 11.9 inches).

Etymology in English

Shaku entered English in the early 18th century,[4] deriving from the Japanese pronunciation of the kanji , the same character as the Chinese chi. (The modern Taiwanese chi actually uses this length as well, while the mainland and Hong Kong chis vary slightly.)

Japanese Official Unit from 1891 to 1966

The shaku had been standardized as 10/33 meter (30.3 centimeters or 11.9 inches) since 1891.[5] This means that there are 3.3 shaku to one meter.[6][7] The use of the unit for official purposes was banned on March 31, 1966, although it is still used in 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.[8] Similarly, the koku remains in use in the Japanese lumber trade.


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),[1] 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).[7][2]

Carpenter's Unit and Tailor's Unit

Another shaku variant used for measuring cloth, which was 125/330 meters (37.9 centimeters or 14.9 inches). It was called the "whale shaku" (鯨尺 kujirajaku), because baleen (whale whiskers) were used as cloth rulers.

To distinguish the two variants of shaku, the general unit was known as the "metal shaku" (金尺/曲尺 kanejaku).[6] The Shōsōin in Nara preserves some antique ivory one-shaku rulers, known as the kōgebachiru-no-shaku (紅牙撥鏤尺).[9][10]

Derived units

Main: cun, zhang, ken, and koku.


Just as with the Chinese unit, the shaku is divided into ten smaller units, known as sun () in Japanese, and ten shaku together form a larger unit known in Japanese as a (). The Japanese also had a third derived unit, the ken, equal to 6 shaku; this was used extensively in traditional Japanese architecture as the distance between supporting pillars in Buddhist temples and Shinto shrines.[2]


Ten cubic shaku comprised a koku, reckoned as the amount of rice necessary to sustain a peasant for a year.

Outside Japanese isles

This Japanese ex-official shaku also forms the basis of the modern Taiwanese chi.

In 1902, the Korean Empire adopted the Japanese definition of the shaku as that of the ja ().

See also


  1. 1 2 Hoffmann, Johann Joseph (1876), A Japanese Grammar, Volume 6 of Classica Japonica facsimile series. Linguistics (2, reprint ed.), E. J. Brill, pp. 166–167
  2. 1 2 3 Heino Engel (1985). Measure and construction of the Japanese house. Tuttle Publishing. p. 22. ISBN 978-0-8048-1492-8.
  3. 説文解字 No.5398 「尺、所以指尺䂓榘事也。」East Asian, including Japanese and Chinese, usually spans with his/her thumb and index finger instead of his/her thumb and little finger.
  4. Oxford English Dictionary, Volume XV page 148Webster's Third New International Dictionary of the English Language, 1986
  5. Japanese Metric Changeover by Joseph B. Reid, President Emeritus, Canadian Metric Association (U.S. Metric Association page)
  6. 1 2 Details of the two shaku units at
  7. 1 2 "尺" [Shaku]. Nihon Kokugo Daijiten (in Japanese). Tokyo: Shogakukan. 2012. OCLC 56431036. Retrieved 2012-10-29.
  8. A note on shakuhachi lengths


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