Celsius (°C) Conversions
The degree Celsius is a unit of temperature on the Celsius scale, a temperature scale originally known as the centigrade scale. Celsius scale based on 0° for the freezing point of water and 100° for the boiling point of water. Invented in 1742 by the Swedish astronomer Anders Celsius, it is sometimes called the centigrade scale because of the 100-degree interval between the defined points.
The degree Celsius symbol is °C, can refer to a specific temperature on the Celsius scale or a unit to indicate a difference between two temperatures or an uncertainty.
Melting and boiling points of water
The melting and boiling points of water are no longer part of the definition of the Celsius scale. In 1948, the definition was changed to use the triple point of water. In 2005 the definition was further refined to use water with precisely defined isotopic composition (VSMOW) for the triple point. In 2019, the definition was changed to use the Boltzmann constant, completely decoupling the definition of the kelvin from the properties of water. Each of these formal definitions left the numerical values of the Celsius scale identical to the prior definition to within the limits of accuracy of the metrology of the time.