Convert Stone (UK) to Kilogram

The stone has ancient origins, dating back to the medieval period. Historically, the weight of a stone varied depending on the commodity being measured, ranging from 5 to 30 pounds. For example, in England, the stone was used to measure wool, and different types of goods had their own stone weights. In 1300, a standardized 14-pound stone was adopted for use in the wool trade. Over time, this 14-pound definition became the standard, and the stone was widely used in the UK for measuring body weight, a tradition that continues today.

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.