“Cun” is the relative unit of measure of distances in the human body used in Chinese Medicine (Traditional Chinese Medicine or TCM).
Like the “inch”, usually understood as deriving from the width of the human thumb (2,54 cm), 1 Cun is the width of the thumb of the person being measured. The genius idea of ancient Chinese doctors is to have developed a relative measure that changes upon the shape of any human body. So, 1 Cun measured in one person can be very different from 1 Cun on another person depending on their dimension and shape.
The Cun varies also within the same person in different regions and it is precisely measured dividing the distance by 2 fixed anatomical landmarks by a convectional number of Cuns.
- The width of the thumb si 1 Cun
- The length of the second phalanx of index finger is 1 Cun
- The width of index and middle finger together is 1,5 Cun
- The width of index to little finger together is 3 Cun
But the more precise way to measure Cuns in the body is to follow the rules in the picture.