Unit Converters

History

The troy ounce is believed to originate from the French city of Troyes, an important medieval trading center. The troy weight system has been used for precious metals since at least the 15th century and remains the international standard for gold and silver pricing today.

History

The kilogram was originally defined in 1799 as the mass of one liter of water at 4°C. For over a century, it was defined by a physical platinum-iridium cylinder kept in Paris. In 2019, the kilogram was redefined in terms of the Planck constant, making it the last SI base unit to be defined by a fundamental physical constant rather than a physical artifact.