Chi (unit)

Chi (unit)
Chinese	尺
Transcriptions Mandarin - Hanyu Pinyin chǐ - Wade–Giles ch'ih Min - Hokkien POJ chhioh Cantonese (Yue) - Jyutping cek3 - Yale Romanization chek3

The chi (Chinese: 尺; Mandarin Pinyin: chǐ; Wade–Giles: ch'ih; Jyutping: cek3) is a traditional Chinese unit of length, approximately equal to one foot. Its length is derived from the length of human forearm and has first appeared during the Shang Dynasty approximately 3,000 years ago. Since then it has spread to and been adopted by other East Asian cultures, such as Japan, Korea and Vietnam. It is further divided into 10 smaller units called cun (Chinese: 寸; Mandarin Pinyin: cùn; Wade–Giles: ts'un; Jyutping: tsun), analogous to an inch; 10 chi make up one zhang (Chinese: 丈; Mandarin Pinyin: zhàng; Wade–Giles: chang; Jyutping: jeung).

1 chi (China) =

SI units
0.3333 m	333.3 mm
US customary / Imperial units
1.094 ft	13.12 in

1 chek (Hong Kong) =

SI units
0.371475 m	371.475 mm
US customary / Imperial units
1.21875 ft	14.6250 in

1 chi (Taiwan) =

SI units
0.3030 m	303.0 mm
US customary / Imperial units
0.9942 ft	11.93 in

Modern values

In People's Republic of China chi has been defined since 1984 as exactly 1/3 of a meter, i.e., 33⅓ cm (approximately 1.094 ft). However, in the Hong Kong SAR the corresponding unit, pronounced chek in Cantonese, is defined as exactly 0.371475 m (exactly 14⅝ in). The two units are sometimes referred to in English as "Chinese foot" and "Hong Kong foot".

In Taiwan, chi is the same as the Japanese shaku, i.e., 10/33 of meter (30⅓ cm).

Historical values

The study of ancient rulers and other artifacts whose size in the contemporary chi was known allowed modern researchers to surmise that during the 2nd century BC to 3rd century AD the (Qin Dynasty to Han Dynasty to Kingdoms of Wu and Wei), the value of the chi varied between 23.1 to 24.3 cm. Even earlier, during the Warring States era, the value of chi was essentially the same.

It is thought that the ancient Chinese astronomers also used chi as an angular unit; modern analysis of historical records indicates that it may have been equal to one degree.

In the 19th century, the value of chi, depending on the part of the country and the application, varied between 31 and 36 cm. According to an 1864 British report, in most of China the chi used by engineers in public works was equal to 12.71 English inches (32.28 cm), the surveyors' chi was 12.058 inches (30.62 cm), while the value generally used for measuring distances was 12.17 inches (30.91 cm). In Guangzhou, however, the chi used for local trade varied from 14.625 to 14.81 inches (37.15–37.62 cm) - i.e., very close to the modern chek. The value fixed by a Sino-British treaty for the purposes of customs duties in Hong Kong was 14.1 inches (35.81 cm).

Art of Bowling

In the art of bowling, bowlers are able to score multiple strikes in a row (referred to as Single, Bacon, Turkey, and Pan depending on the number consecutive of strikes) based on the amount of chi sent from the bowler to the bowling ball. Poor frames in bowling are often blamed on poor chi distribution. A result of poor chi distribution leads to people snickering, "You're one chi too much to the left," or "I believe you have overexerted yourself with the chi."

Usage in Chinese

A section of an old Hong Kong ruler, showing the last (10th) cun of a chi. One can see that the chi in that jurisdiction was exactly equal to 14 and 5/8 of an inch. A metric ruler is shown next to it for comparison

Due to its long history and its widespread usage, chi (along with cun) has also seen metaphorical usages in the Chinese language. For example, chi cun (Chinese: 尺寸), a word made up of the units chi and cun, refers to the dimensions of an object, while the idiom "dé cùn jùn chǐ" (simplified Chinese: 得寸进尺; traditional Chinese: 得寸進尺; literally "gaining a cun and ask for a chi") means "extremely greedy".

See also

• Shaku (unit) - the corresponding unit in Japanese
• Chinese units of measurement
• Taiwanese units of measurement