Cun (unit)
![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](/Images/godic/202502/18/Hong_Kong_ruler_close-up_0024647.jpg")
![Model of Himeji Castle](/Images/godic/202502/18/Himeji_model74647.JPG")
The cun (Chinese:寸; pinyin:cùn; Wade–Giles:ts'un; Japanese: sun; Korean: chon) 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 all fingers side-by-side is three cuns. In this sense it continues to be used to chart acupuncture points on the human body in various uses of traditional Chinese medicine.