The issue about the weight conversion in terms of prescription in Chinese Medicine from Liang (兩) used in Shang Han Lun (傷寒論), written in Han (漢) dynasty, into the unit, Grams, has beencontroversial for a long time. Four different perspectives exist among the Chinese medicine practitioners: 1 liang is equal to 15.6 grams, 3.75 grams, 1.3 grams, and 13.75 grams, respectively. Yet, nowadays, most Chinese Medicine practitioners prescribe followed a saying that “1 liang is equal to 1 qian (錢),” where 1 qian is considered to be 3.75 grams, from both Li Shizhen (李時珍), the author of Compendium of Materia Medica (本草綱目), and Wang Ang (汪昂), the complier of Tangtou Gejue (湯頭歌訣), yet both reflect the weight unit used in Ming (明) dynasty rather than in Han (漢) dynasty.
Meanwhile, in a Chinese medicine formula, there are several herbs measured in different unit such as weight, numbers, and volume. In a formula with different measurement, there will be a dramatic difference applying all herbs into a weight unit based on an equation that “1 liang is equal to 1 qian”. There is apparently a significant gap between the amount of medicine used in Shang Han Lun and the amount most Chinese medicine practitioners applied nowadays due to the discrepancy of the weight units. This study attempted to use a practical way to approach the historical problem, and reached the conclusion that 1 liang described in Shang Han Lun should be equal to 13.75 grams.