Convert Kilogram to Ton (assay) (US)

The kilogram originated during the French Revolution in the late 18th century as part of the metric system's development. Initially, it was defined as the mass of one cubic decimeter of pure water at 4°C, chosen for its universal availability and consistency. In 1799, a physical standard called the Kilogram of the Archives, a platinum cylinder, was created to represent the unit. Later, in 1889, the International Prototype of the Kilogram (IPK), a more precise platinum-iridium cylinder, was adopted as the global standard, stored in France with copies distributed worldwide.

Over time, physical changes in the IPK led to inconsistencies, prompting scientists to redefine the kilogram. In 2019, it was redefined based on the Planck constant (h), a fundamental constant of nature, linking the kilogram to unchanging physical properties rather than a physical object. This modern definition ensures long-term precision and stability for the unit of mass.

The ton assay originated in the United States as a unit of mass for assaying precious metals. It was defined as 29.16666667 kilograms or approximately 64.58333333 pounds. The term "ton assay" comes from the practice of assaying, which is the process of determining the content of precious metals in ore samples. The ton assay is used in the United States for this purpose.