To determine the location of an acupoint, in addition to using surface landmarks and the bone proportional method, one can also use finger measurements based on proportional body segments. The fingers of a normal person have a certain proportional relationship with other parts of the body; longer people have longer fingers, and shorter people have shorter fingers. Therefore, measuring an acupoint is based on using a segment of one's own finger length or width as a standard unit, called "body cun." Qianjin Yifang Volume 26 states: "People vary in height and size, so the patient's hand should be used as a measure." However, if both the practitioner and the patient are adults, the practitioner's fingers can be used for measurement. For children or individuals with significant height differences, the measurements should be adjusted proportionally.

The finger measurements commonly used include the following:

Hand-based body cun measurement

1. When the middle finger is bent, the distance between the two transverse creases at the side of the middle segment is considered "one cun." This method is recorded in the Song Dynasty text Taiping Shenghui Fang, and later generations referred to it as the "middle finger body cun." Tang Dynasty texts such as Qianjin Yaofang and Waitai Miyao use the length of the distal segment of the middle finger as one cun.

2. The width of the distal segment of the thumb is considered "one cun." This method is found in Qianjin Yaofang.

3. When the index finger is extended, the length of the middle and distal segments is considered "two cun."

4. The combined width of the index and middle fingers (two fingers side by side) is considered "one and a half cun."

5. The combined width of the index, middle, ring, and little fingers (four fingers side by side) is considered "three cun," also known as "one fu." The term "fu" (夫) is related to "support." (扶) The Book of Rites notes: "Supporting four fingers is called 'fu' (扶)." Qianjin Yaofang states: "The method of measuring one fu involves placing the hand flat and extending four fingers, measuring the width across the middle segments of the four fingers as one fu." This method is often used for vertical measurements on the lower limbs and lower abdomen, as well as horizontal measurements on the back.

The finger measurement method must be applied based on the bone proportional system. It should not be used to measure all parts of the body by simply multiplying finger units, as this could lead to inaccuracies due to varying body proportions. Zhang Jingyue's Leijing Tuyi states: "Body cun refers to measurements proportional to the individual's body. People vary in height and build, and the horizontal and vertical measurements of acupoints cannot be uniform. If the middle finger body-cun method is applied indiscriminately, it would lead to errors, as a thin person with long fingers and a stout person with short fingers would not align. Therefore, measurements must be adjusted according to the individual's body shape to be accurate... Thus, the head must be measured according to the head, the abdomen according to the abdomen, the back according to the back, and the limbs according to the limbs. By averaging the length and size, one can achieve a proper body cun method... While the middle finger body-cun method should not be used indiscriminately, it still has its appropriate applications."