Cun (unit)

Cun
Chinese name
Chinese
Transcriptions
Standard Mandarin
Hanyu Pinyincùn
Wade–Gilests'un4
IPA[tsʰwə̂n]
Japanese name
Kanji
Kanaすん
Transcriptions
Revised Hepburnsun
Korean name
Hangul
Hanjan/a
Transcriptions
Revised Romanizationchi
McCune–Reischauerch'i
Alternative Korean name
Hangul
Hanja
Transcriptions
Revised Romanizationchon
McCune–Reischauerch'on
Vietnamese name
Vietnamesethốn
Cun
Wooden ruler of the western Han dynasty, unearthed at Jinguan Pass Site in Jinta County
General information
Unit systemChinese unit
Unit oflength
Conversions
1 cun in ...... is equal to ...
   metric (SI) units   1/30 m
~33.33 mm
   imperial/US units   ~1.3123 in
Tsun
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+5/8 of an inch. A metric ruler is shown next to it for comparison.
General information
Unit systemChinese unit
Unit oflength
Conversions
1 tsun in ...... is equal to ...
   metric (SI) units   37.1475 mm
   imperial/US units   ⁠1+37/80 in
Sun
Unit systemJapanese unit
Unit oflength
Conversions
1 sun in ...... is equal to ...
   metric (SI) units   133 m
~30.30 mm
   imperial/US units   ~1.1930 in

A cun (Chinese: ts'wun; Pinyin cùn IPA |mi=[tsʰwə̂n]), often glossed as the Chinese inch, is a traditional Chinese unit of length. Its traditional measure is the width of a person's thumb at the knuckle, whereas the width of the two forefingers denotes 1.5 cun and the width of four fingers (except the thumb) side-by-side is 3 cuns.[1] It continues to be used to chart acupuncture points on the human body, and, in various uses for traditional Chinese medicine.

The cun was part of a larger decimal system. A cun was made up of 10 fen, which depending on the period approximated lengths or widths of millet grains,[2] and represented one-tenth of a chi ("Chinese foot").[3] In time the lengths were standardized, although to different values in different jurisdictions. (See Chi (unit) for details.)

In Hong Kong, using the traditional standard, it measures ~3.715 cm (~1.463 in) and is written "tsun".[4] In the twentieth century in the Republic of China, the lengths were standardized to fit with the metric system, and in current usage in People's Republic of China and Taiwan[citation needed] it measures ⁠3+1/3 cm (~1.312 in).

In Japan, the corresponding unit, sun (), was standardized at 100033 mm (3.03 cm, ~1.193 in, or ~0.09942 ft).

  1. ^ "TCM Student: Cun Measurements". www.tcmstudent.com. Retrieved 2018-02-10.
  2. ^ Chu, Feng-chieh. Binkley, Jim (ed.). "Yu-Ku-Chai: Vol 2, Chapter 3: Deliberations over Accurate Measurements". web.cecs.pdx.edu. https://web.cecs.pdx.edu/~jrb/chin/. Retrieved 2022-03-10.
  3. ^ Keightley, David N. (1995). "A Measure of Man in Early China: In Search of the Neolithic Inch". Chinese Science (12): 18–40. ISSN 0361-9001. JSTOR 43290484.
  4. ^ Cap. 68 WEIGHTS AND MEASURES ORDINANCE