Units of mass

• SUMMARY: A variety of measurement systems have been used throughout history to measure weight and mass.

Throughout history, there have been many ways of measuring mass. Until modern times, these methods were those used to measure what was known as “weight.” A number of ways of assessing weight existed in prehistoric times. The Sumerians used a system similar to that later used throughout the ancient Middle East, with 180 grains making a shekel (or gin), and 60 of these forming a pound (or ma-na), and 600 of these making a load (or gun). A wall painting from ancient Egypt, dating from 1285 BCE, shows the god Anubis weighing the heart of Hunefer using scales, indicating that the Egyptians had a system of using weights and measures. There were, however, slight differences between the Middle Kingdom and the New Kingdom in Egypt.

Greeks and Romans

The Greeks, with the extensive use of coinage, used a scale that was based on the barley corn but it was actually more fixed on the weight of individual coins. The Romans adapted the Greek system for their own use, with the basic measure of an uncia (or ounce). Twelve of these made up one as, with different names were given to parts of an as: quadrans were a quarter of an as and semis were half an as.

Middle Ages

During the Middle Ages in Europe, a number of measures were used for a variety of purposes. For apothecaries, jewelers, and the making of coins, there were “grains,” “scruples,” and “drams.” Two systems were heavily used in Western Europe. The Troy weights, named after the French city of Troyes, were based on the troy ounce (the name “ounce” coming from the Roman “uncia”). By contrast, in England, until 1526, there was the Tower ounce, which was slightly lighter than its continental measure (18.75 dwt/pennyweight, rather than the Troy ounce which was 20 dwt). For both measures, 12 ounces made up a pound. In England, eight pounds equaled a “butcher’s stone,” and 12 pounds a “mercantile stone.” The larger measurements were in tons, which consisted of 2,240 pounds—now known as a “long ton.” The United States later adopted a measure in which 2,000 pounds equals a “short ton.”

Throughout Europe, there were regional varieties and customary names. Scotland was divided between using the “Troy” measures, and the “Tron” measures, the latter being used in Edinburgh—the system was standardized in 1661. The Portuguese used a system maintained at a national level and was based on the onca (ounce), with 16 of these making an arratel (pound), 128 arráteis making a quintal, and 1,728 making a tonelada. These Portuguese measures, also used in Brazil, were abandoned when both countries adopted the metric system: Portugal and its colonies (or overseas provinces) in 1852 and Brazil ten years later. The Russians also had their own system, which had emerged from that used by the Mongols—although Peter the Great (r. 1682–1725) overhauled the system and used one based on the English system.

Asia

There were many other systems of measuring mass. In China, people used a system with 1,000 cash making a tael, and ten taels equaling a catty, and 100 of those making up a picul. In Japan, the system relied on the momme (about 3.75 g), with 100 of these forming a hyakume, 160 of them making one kin, and 1,000 of them equaling one kan. The momme is still used as a measure of mass in the pearling industry, which is still dominated by Japan.

Modern Measurements

The base SI unit of mass measurement is the kilogram (kg), which equals one megagram (Mg) or one metric ton (t). The kilogram is defined using Planck’s constant (h), the gravitational constant, as 6.62607015 ×10⁻³⁴. Grams and kilograms are most commonly used in daily life. Other units include decigrams, centigrams, milligrams, dekagrams, and hectograms. In the United States, the US Customary Systems of Measurement are commonly used, with the base unit pounds (lbs) to measure mass. One pound is equal to 0.45359237 kilograms. Ounces (oz) are the smallest units, with 16 ounces equaling one pound. Tons (t) are large units, with 2,000 pounds equaling one US ton. However, these should not be confused with imperial or metric tons, as those share the name but are different measurements.

Bibliography

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Fenna, Donald. A Dictionary of Weights, Measures, and Units. Oxford UP, 2002.

Grayson, Michael A. Measuring Mass: From Positive Rays to Proteins. Chemical Heritage Foundation, 2005.

"History of Measurements." Vitrek, vitrek.com/mti-instruments/knowledge-center/history-of-measurements. Accessed 1 Oct. 2024.

Moody, Ernest A. The Medieval Science of Weights. U of Wisconsin P, 1960.

"SI Units - Mass." Office of Weights and Measures, National Institute of Standards and Technology, 16 Jan. 2024, www.nist.gov/pml/owm/si-units-mass. Accessed 1 Oct. 2024.

Zupko, R. E. “Medieval Apothecary Weights and Measures: The Principal Units of England and France.” Pharmacy in History, vol. 32, no. 2, 1990, pp. 57–62.