Degree Celsius (°C)

Metric (SI)Current unit

The metric temperature scale used worldwide for weather and daily life: water freezes at 0 °C and boils at 100 °C at standard pressure. Named after Anders Celsius.

0 degrees Celsius = 273.15 kelvins (exactly).

About the degree Celsius

Anders Celsius, a Swedish astronomer, proposed a scale in 1742 that ran the opposite way from the one we use: 0 for the boiling point of water and 100 for its freezing point. Credit for flipping it is shared and partly disputed. French physicist Jean-Pierre Christin published a reversed mercury thermometer in 1743, Carl Linnaeus is usually credited with reversing it in 1744, the year Celsius died, and others in Sweden, including Pehr Elvius, Daniel Ekström and Mårten Strömer, are also named as independent developers.

For much of the nineteenth century the scale was called centigrade, until the CGPM and CIPM adopted the name degree Celsius in 1948, partly to honor Celsius and to avoid confusion with a French term for a subdivision of the gradian. From 1954 to 2019 it was defined through absolute zero and the triple point of water; since 2019 it is tied to the Boltzmann constant. Strictly, water boils at about 99.974 degrees on the modern international temperature scale, not exactly 100. Australian weather reports switched exclusively to Celsius in 1972.

Sources: Wikipedia: Celsius; BIPM: 9th CGPM (1948), Resolution 7; NIST: the kelvin and the SI redefinition

Degree Celsius conversion chart

100 degrees Celsius expressed in every other temperature unit:

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