What is the length of the arm measured in cun?

The length of the arm measured in cun is indeed typically considered to be 9 cun. In traditional Chinese medicine, the cun is a unit of measurement that is based on the width of a person's thumb and is used for acupuncture point location and anatomical measurements.

To understand why 9 cun is the accepted measurement for the length of the arm, it’s important to note that the cun measurement scale varies across different parts of the body. The arm is often measured from the elbow to the tip of the middle finger, which roughly corresponds to this standard length.

This measurement helps practitioners accurately locate acupuncture points based on standardized anatomical references. By using the cun as a unit of measure, acupuncturists can create a more reliable and effective treatment plan. This standardization is essential in a clinical setting to ensure consistency and precision in practice.