Celsius

**Celsius temperature conversion formulas**
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

A degree Celsius (°C) is a unit of temperature named after the Swedish astronomer Anders Celsius (1701-1744), who first proposed a similar system in 1742. From around 1750 the scale was known as the Centigrade scale, and though it was renamed after Celsius in 1948, the older name is still in widespread use. One reason for the change was that the term centigrade was in use in continental Europe as a measure of plane angle equal to one ten-thousandth part of a right angle.

The Celsius scale sets 0.01 °C to be at the triple point (the temperature and pressure at which three phases href="http://articles.gourt.com/en/gas">gas, liquid, and solid of that substance may coexist in thermodynamic equilibrium) of water and a degree Celsius to be 1/273.16 of the difference in temperature between the triple point of water and absolute zero. Until 1954 the scale was defined with the freezing point of water at 0 °C and the boiling point at 100 °C at standard atmospheric pressure. This definition is still a close approximation to the modern definition.

History

In the original scale devised by Anders Celsius the boiling point of water at 1,000 millibars was defined as 0 degrees and the freezing point of water was defined as 100 degrees, exactly the reverse of the modern Celsius scale. It was then reversed to its modern order some time shortly after his death, in part at the instigation of Daniel Ekström, the Swedish manufacturer of most of the thermometers used by Celsius. Several other people, including the Swede Per Elvius the Elder (1710) and the Frenchman 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, particularly in connection with one hundredth of a Grad. While the values for freezing and boiling of water remain approximately correct, they are no longer suitable as reference points for a formal standard. The current official definition of the Celsius scale sets 0.01 °C 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 of the degree was adopted in 1954 at the 10th General Conference on Weights and Measures, the very same definition given for the kelvin degree (but 0 K is not 0°C). For the practical calibration of thermometers, the International Temperature Scale of 1990 defines many additional reference points.

Naming

The degree Celsius is the only SI unit whose full unit name ("degree Celsius", not "Celsius") in English includes an upper case letter. (Before the name was changed from "degree Kelvin" to "kelvin" in 1967, that was another SI unit containing a capital letter in English.) While SI prefixes could be applied in principle, they are not used in practice (ISO 1000).

Application

The Celsius scale is the world's most commonly used temperature scale. It has been adopted by virtually all the countries of the world, with the notable exceptions of the United States of America and Jamaica. 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.

The Unicode character set contains a dedicated precomposed degrees Celsius character (℃, U+2103). This character was only intended for compatibility mapping of legacy character sets that contain it as well. It should not be used in new texts.

References

Basic unit definitions: Kelvin
centigrade
Understanding Temperature and Transmitters
AJ Metric Handbook, 3rd edition 1969, Architectural Press, London.

SI derived units | Units of temperature

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History

Naming

Application

References