Celsius
| Conversion from | to | Formula |
|---|---|---|
| Celsius | Fahrenheit | °F = °C × 1.8 + 32 |
| Fahrenheit | Celsius | °C = (°F – 32) / 1.8 |
| Celsius | kelvin | K = °C + 273.15 |
| kelvin | Celsius | °C = K – 273.15 |
| Additional conversion formulas Conversion calculator for units of temperature | ||
The degree Celsius (°C or ℃ (Unicode 0x2103)) is a unit of temperature named after the Swedish astronomer Anders Celsius (1701–1744), who first proposed a similar system in 1742. The Celsius temperature scale was originally designed so that the freezing point of water is 100 degrees, and its boiling point is 0 degrees at standard atmospheric pressure. This was reversed to its modern order some time after his death, in part at the instigation of Daniel Ekström, the manufacturer of most of the thermometers used by Celsius. Several other people, including Elvius from Sweden (1710) and Christian of Lyons (1743), independently invented the same temperature scale. The oft-quoted claim that the botanist Carolus Linnaeus (1740) is amongst those is unsubstantiated. The Delisle scale was another temperature scale that ran "downward".
Since there are one hundred graduations between these two reference points, the original term for this system was centigrade (100 parts) or centesimal. In 1948 the system's name was officially changed to Celsius (a third name which had also been in use before then) by the 9th General Conference on Weights and Measures (CR 64), both in recognition of Celsius himself and to eliminate confusion caused by conflict with the use of the SI centi- prefix. While the values for freezing and boiling of water remain approximately correct, the original definition is unsuitable as a formal standard: it depends on the definition of standard atmospheric pressure which in turn depends on the definition of temperature. The current official definition of the Celsius sets 0.01 ℃ to be at the triple point of water and a degree to be 1/273.16 of the difference in temperature between the triple point of water and absolute zero. This definition was adopted in 1954 at the 10th General Conference on Weights and Measures, the very same definition given for the kelvin.
The degree Celsius is the only SI unit whose full unit name ("degree Celsius", not "Celsius") in English includes an upper case letter. That is a quirk of English, because it is a proper adjective rather than a noun (before the name was changed from "degree Kelvin" to "kelvin" in 1967, that was another SI unit containing a capital letter in English). SI prefixes are applied normally, so you can have, for example, a measurement of « 12 m℃ ».
The Celsius scale is used throughout most of the world for day-to-day purposes. In broadcast media it was still frequently referred to as centigrade until the late 1980s or early 1990s, particularly by weather forecasters on European networks such as the BBC, ITV, and RTÉ. In the United States and Jamaica, Fahrenheit remains the preferred scale for everyday temperature measurement, although Celsius or kelvin is used for aeronautical and scientific applications.
In the United Kingdom, Celsius is the official scale used by the government and the media. It is also the only scale used in British cooking and temperature controllers (for example, room thermostats). Some of the British media, however, still provide Fahrenheit equivalents since many in Britain, especially older people, still use the Fahrenheit scale. Even so, many that do still switch to the use of Celsius for low temperatures.