In daily life, people often say a certain container can hold "a few liang and a few qian" of wine. This statement is actually not very accurate. "Qian" and "liang" are units of measurement, not units of volume, and have existed since ancient times. This article focuses on the unit of measurement, "qian," which originated in the Tang Dynasty. The "Book of Han: Records of the Calendar" states, "The five liangs are zhu, liang, jin, jun, and shi. They are used to measure the distribution of objects and to determine their weight. They originated from the weight of the Huangzhong. A flute can hold 1,200 grains of millet and weighs 12 zhu. Two liangs make a liang. Twenty-four zhu make a liang, sixteen liang make a jin, thirty jin make a jun, and four jun make a shi... The system of the five liangs was established based on morality and quantified by the objects themselves. Other differences in size are based on weight." Therefore, 1 zhu = 100 grains of millet, 1 liang = 24 zhu, 1 jin = 16 liang, 1 jun = 30 jin, and 1 shi = 4 jun. It's also easy to see that the conversion relationships between the five basic units of weight and scale described in the "Book of Han: Lüli Zhi" are not based on decimals. It states, "Twenty-four zhu make a liang, representing the twenty-four solar terms... Sixteen liang make a jin, representing the four seasons multiplied by the four directions... Thirty jin make a jun, representing one month... Four jun make a shi, representing the four seasons." The "Huainanzi," written in the Western Han Dynasty and predating the "Book of Han: Lüli Zhi," also contains similar records: "There are four seasons in the sky, making up a year. Therefore, multiplying four by four equals sixteen. Therefore, sixteen liang make one jin; three months make one hour, and thirty days make one month. Therefore, thirty jin make one jun; four seasons make up a year, so four jun make one shi." Moreover, there is uncertainty in determining the weight standard by the method of “Huang Zhong Tube” and “determining weight by millet”. In the above statement “it originated from the weight of Huang Zhong, one flute can contain 1,200 millets and weighs 12 zhu”, both “Huang Zhong Tube” and “millet” are subject to variables. From the perspective of “Huang Zhong”, “Huang Zhong changes with the sound of the bell, so the Huang Zhong of different dynasties is not the same[4]”. From the perspective of “millet”, as a natural object, there is even more uncertainty. The “Song History·Lülizhi” records that “years have good harvests and bad harvests, and land has barrenness and fertility. Even in one year, within one region, the results of verification are still not uniform. This is because the creation of natural objects is difficult to be uniform... The ancient laws only kept the general idea.” There is a similar record in “Tiangong Kaiwu”: “the size of millet grains depends on the fertility of the land and the seasonal changes. The Song Confucianists were not rigidly bound by a certain millet law.” However, although the units of measurement are not decimal and there are variables in "Huangzhong Lüguan" and "Shu", the above theory is the most complete, systematic and authoritative treatise on the weight standard of weights and measures in ancient my country. It has influenced the development of China's weights and measures for nearly 2,000 years and has been regarded as a standard and model by all dynasties. In the Tang Dynasty, the ancient Chinese weight system developed. In addition to the five basic units of "zhu, liang, jin, jun and shi", a new unit "qian" appeared. According to the "Tang Huiyao", "In the fourth year of Wude in the Tang Dynasty [5], Kaiyuan Tongbao coins were cast, with a diameter of eight fen and a weight of two zhu and four si". According to the Qing Dynasty's "Gujin Tushu Jicheng", "Kaiyuan Tongbao coins were cast in the fourth year of Wude in the Tang Dynasty... Ten coins weighed one liang... The so-called two zhu and four si is now the weight of one qian in the Qing Dynasty". Talking about "qian" in weights and measures
□Zheng Ying [1]  Yang Yangzhongfu [2]  Zheng Qinyu [3]
Document code: B Article number: 1003-1870 (2025) 04-0055-02
About "qian" in weights and measures
[1] Author's unit: Planning and Finance Department of the State Administration for Market Regulation
[2] Author's unit: China Institute of Measurement and Testing
[3] Author's unit: No. 171 Middle School, Beijing
[4] Wu Chengluo. History of Chinese Weights and Measures [M]. Shanghai: Sanlian Bookstore, 2014: 32
[5] [ ] is the author's note, the same below
1
From these two paragraphs, we can see that the weight of a Kaiyuan Tongbao coin in the Wude period of the Tang Dynasty was two zhu and four si. Since 1 zhu = 10 si, two zhu and four si is 2.4 zhu, and the weight of 10 Kaiyuan Tongbao coins is exactly 24 Zhu is 1 Liang, so the weight of a Tang Kaiyuan Tongbao coin is exactly 1/10 Liang. In this way, "Qian" replaced "Zhu" to form a new unit of measurement with a decimal system between "Liang", 1 Liang = 10 Qian. In the naming of units of measurement in the Song Dynasty, "Zhu" was gradually abandoned, and under the unit of measurement "Qian" established in the Tang Dynasty, "Fen", "Li", "Hao", "Si", "Hu" and other units of measurement were added. These units under "Qian" were originally units of measurement. "Moving the length unit to the measurement system was an innovation of the Song Dynasty[6]". In the Song Dynasty and after the Song Dynasty, the main units of measurement were "Shi", "Jun", "Cheng", "Jin", "Liang", "Qian", "Fen", "Li", "Hao", "Si", "Hu", etc. Among them, the conversion between the units under "Liang" was all decimal. As recorded in the "Song History: Records of the Calendar and Lü" (Lüli Zhi), "a hu is ten thousand, a fen is a thousand, a hao is a hundred, a li is ten, and so on, multiplied tenfold..." This means that 1 liang = 10 qian, 1 qian = 10 fen, 1 fen = 10 li, 1 li = 10 hao, 1 hao = 10 si, and 1 si = 10 hu.

Since the Tang Dynasty, when the unit of measurement "qian" emerged, as mentioned above, due to the uncertainty of the "Huangzhong Lüguan" and "the fixed weight of millet," the value of the qian has varied throughout the dynasties since the Tang Dynasty. During the Tang Dynasty, 1 qian was equivalent to approximately 4.169 grams; during the Song and Yuan Dynasties, 1 qian was equivalent to approximately 4 grams; and during the Ming and Qing Dynasties, 1 qian was equivalent to approximately 3.73 grams. During the "New Deal" of the late Qing Dynasty, to promote the unification of weights and measures, the Ministry of Agriculture, Industry, and Commerce and the Ministry of Finance jointly drafted the "General Table of Weights and Measures" in 1908, which still "adhered strictly to the ancestral system" and adopted the "Yingzao Chi Kuping System." This stipulated that 1 tael (Kuping Liang) equaled 37.301 grams, and 1 qian (Qian) equaled 3.73 grams. At the beginning of the Republic of China, the "Weights and Measures Law" promulgated by the Beijing government in 1915 clarified two legal weights and measures systems. The "A System" adopted the "Yingzao Chi Kuping System" and stipulated that "at 4 degrees Celsius on a 100-degree thermometer, the weight of one cubic cun (1 cun = 3.2 cm) of pure water is 0.878475 taels." Therefore, 1 tael = [(3.2 cm)3 × 1 gram/cubic centimeter] / 0.878475 = 37.301 grams. At the same time, the "A system" stipulated that all weight units below the "jin" (jin) be converted to the decimal system: "hao" (hao), "qian" (qian), "fen" (fen), "li" (li), and "hao" (hao). This meant that "hao equals 0.0001 liang, li equals 0.001 liang (10 hao), fen equals 0.01 liang (10 li), qian equals 0.1 liang (10 fen), and liang equals 16 liang." Therefore, 1 qian equals 1/10 liang (3.73 grams). Following the victory of the Northern Expedition, the "Weights and Measures Law" promulgated by the Nanjing government of the Republic of China in 1929 established the "standard system [metric]" and supplemented it with the "city system." The law also specified that "the city system is based on one-half of a kilogram as a jin... One jin is divided into 16 liang." Therefore, 1 jin equals 16 liang (500 grams), and 1 liang equals 31.25 grams. The "Market Use System" stipulates that the conversions between "liang," "qian," "fen," "li," "hao," and "si" (the "Measures and Measures Law" reinstated "si" but the "Weights and Measures Law" had eliminated it) below the "jin" (a jin) are all to be decimalized, i.e., "si" equals one millionth, six hundred thousandth of a jin (0.000000625 jin), "hao" equals one sixteen thousandth of a jin (10 si) (0.00000625 jin), "li" equals one sixteen thousandth of a jin (10 hao) (0.0000625 jin), "fen" equals one thousand six hundredth of a jin (10 li) (0.000625 jin), "qian" equals one hundred and sixty-first of a jin (10 qian) (0.00625 jin), and "liang" equals one sixteenth of a jin (10 qian) (0.0625 jin). Therefore, 1 qian = 1/10 of a liang = 3.125 grams. During the first half of the 21st century, the revolutionary base areas under the leadership of the Chinese Communist Party (CCP) during its period of partial rule employed varying values of the "jin" (jin) due to the historical conditions and wartime environment. Based on the system of 1 jin = 16 liang = 160 qian (qian), the "shi jin" (market jin) had a value of 1 qian = 3.125 grams; the "kuping jin" (Kuping jin) had a value of 1 qian = 3.73 grams; the "sima jin" (Sima jin) had a value of 1 qian = 3.97 grams; and the "caocheng jin" (Caocheng jin) had a value of 1 qian = 3.665 grams. Of course, in addition to the "shi jin," "kuping jin," "sima jin," and "caocheng jin," the revolutionary base areas also used other "mixed jins." The Northeast Liberated Area used a 10-liang jin (jin), while other revolutionary base areas primarily used a 16-liang jin (jin). In summary, the term "qian" as a unit of measurement originates from the weight of the Kaiyuan Tongbao coins of the Tang Dynasty. In fact, the practice of using currency as a benchmark for weights and measures predates the Tang Dynasty, as exemplified by the Qin Banliang (half-liang) coin and the Han Wuzhu (five-zhu) coin. Furthermore, in modern times, Mr. Wu Chengluo published an article in the 6th issue of "Industrial Standards and Weights and Measures" in 1936, expounding on the relationship between coins and weights and measures during the Republic of China period.