Degree Celsius

The degree Celsius (symbol in ° C) is the unit of a temperature measurement scale , named after the Swedish astronomer Anders Celsius (1701 – 1744), who first proposed it in 1742. The Celsius scale is a scale to indicate the temperature at which the temperature ranges are degrees Celsius.

The Celsius scale defines the melting point of ice in a mixture of water saturated with air at 0 ° C and the boiling point at 99.974 ° C under standard pressure conditions (1 bar, slightly less than the atmosphere, pressure to water) boils at 100 degrees Celsius).

Originally conceived by the Celsius scale, it had a boiling point of water at 0 ° C and a freezing point of 100 ° C. After his death, however, the scale was reversed in 1745 by Linnaeus, transforming it into what is now commonly used.

The current official definition of the Celsius scale places 0.01 ° C as a triple point of water and a degree as 1 / 273.16 of the temperature difference between the triple point of water and absolute zero. This definition of degrees Celsius ensures that the temperature difference of one degree Celsius represents the same temperature difference as a Kelvin.


Formulas for converting degrees Celsius to other temperature units.

  • Conversion of degrees Celsius to degrees Fahrenheit at ° F = (9/5 × ° C) + 32
  • Conversion of degrees Fahrenheit to degrees Celsius at ° C = (5/9) × (° F – 32)
  • Conversion of degrees Celsius to kelvin at K = ° C + 273.15
  • Conversion Kelvin to degrees Celsius ° K = – 273.15

Anders Celsius originally proposed that the water freezing point be 100 ° C and the boiling point 0 ° C. The ladder was reversed in 1745 at the suggestion of Linnaeus, or perhaps by Daniel Ekström, producer of most of the thermometers used by Celsius.

The Celsius and Fahrenheit thermometric scales cross at the same value of -40 degrees, that is, the value of -40 ° C corresponds to -40 ° F.

One way to convert Celsius to Fahrenheit is to multiply by 1.8 and add 32.

° F = ° C × 1,8 + 32

On the other hand, to convert Fahrenheit to degrees Celsius, subtract 32 and divide by 1.8.

° C = (° F – 32) / 1,8

The Celsius scale is used daily in most parts of the world, although in mass media it is still called centigrade until the 1990s, especially in weather forecasts. In the United States (as well as in non-corporate territories and freely associated states of the Pacific), in Belize, Liberia and some Caribbean islands, the Fahrenheit scale is used, but these countries also use the Celsius or Kelvin scale in Applications. scientific or technological.

Other temperature ranges are: Newton (around 1700), Rømer (1701), Fahrenheit (1724), Réaumur (1731), Delisle or de Lisle (1738), Rankine (1859), Kelvin (1862) and Leyden (by around 1894). Note that “kelvin” is tiny, because it is an SI unit, even though it is derived from the noble title of scientist William Thomson.


Since there are a hundred divisions between these two landmarks, the original term for this system was either centigrade or centesimal. In 1948, the ninth General Conference of Animals (CR 64) officially changed its name to Celsius to remove several ambiguities:

  • the centi prefix is ​​used by the SI system for submultiples;
  • a more correct name, at least since Linnaeus was invested, would have been “hectograd”;
  • the hectogram is also ambiguous and, in oenology, indicates the alcohol content per hectolitre of wine;
  • the term “degrees centigrade” was also used to indicate the hundredth degree used to measure angles;
  • Kelvin is also a degree centigrade, in that it is obtained, like Celsius, by dividing the interval between two fundamental fixed points in equal parts.

The decision of the Conférence générale des poids et mesures aimed to remove ambiguities and to unequivocally associate the creation of the scale with Celsius (despite Linnaeus’ important contribution); in addition, the scale was standardized with those of Kelvin (created by Lord Kelvin), Fahrenheit, Réaumur and Rankine , all named after their inventor.

Despite this, there are often people who refer to degrees centigrade as “degrees Celsius”, just as they use the centigrade concept scale.


The existence of an absolute temperature scale is a consequence of the second principle of thermodynamics .

According to the second law, the absolute temperature scale starts from the existence of 0º absolute. This condition is met only by two basic units:

  • Degree of Kelvin
  • Grau Rankine.

Zero degrees Kelvin corresponds to -273.16 degrees Celsius.Author: Oriol Planas – Industrial Technical Engineer, specializing in mechanics

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