Shaku (unit)

The shaku (Japanese: 尺) or Japanese foot 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 (compare span). Traditionally, the length varied by location or use, but it is now standardized as 10/33 m, or approximately 30.3 centimeters (11.9 in).

Shaku entered English in the early 18th century, a romanization of the Japanese Go-on reading of the character for Japanese foot (尺, shaku).

The shaku has been standardized since 1891 as 10⁄33 m, about 30.3 cm (11.93 in). This means that there are 3.3 shaku (33⁄10) to one meter.

This definition was established by Meiji government law; until then, even though the unit was given the same name, its length varied depending on the era. At the same time, other units were established based on shaku.

明治二十四年（1891年）三月二十四日法律第三號 度量衡法
第四條 從來慣用ノ鯨尺ハ布帛ヲ度ルトキニ限リ之ヲ用ヰルコトヲ得
鯨尺一尺ハ一尺二寸五分トシ其ノ十倍ヲ鯨尺一丈、十分ノ一ヲ鯨尺一寸、百分ノ一ヲ鯨尺一分トス

English：1Shaku = 10sun = 100bu
Japanese：1尺 = 10寸 = 100分

The use of the unit for official purposes in Japan was banned on March 31, 1966, although it is still used in traditional Japanese carpentry and some other fields, such as kimono construction. 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. In the Japanese construction industry, the standard sizes of drywall, plywood, and other sheet goods are based on shaku, with the most common width being three shaku (rounded up to 910 mm (35.83 in)).

In Japanese media parlance, shaku refers to screen time: the amount of time someone or something is shown on screen (similar to the English "footage").