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

A degree Celsius (°C) is a unit of temperature named after the Swedish astronomer Anders Celsius.

## Definition

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.

## Naming

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). 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 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 [1], Celsius is the official scale used by Athe government and the media. It is also the only scale used in 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.

Comparison of temperature scales
Comment Kelvin Celsius Fahrenheit Rankine Delisle Newton Réaumur Rømer
Absolute zero 0 −273.15 −459.67 0 559.725 −90.14 −218.52 −135.90
Fahrenheit's ice/salt mixture 255.37 −17.78 0 459.67 176.67 −5.87 −14.22 −1.83
Water freezes (at standard pressure) 273.15 0 32 491.67 150 0 0 7.5
Average human body temperature 310.0 36.8 98.2 557.9 94.5 12.21 29.6 26.925
Water boils (at standard pressure) 373.15 100 212 671.67 0 33 80 60
Titanium melts 1941 1668 3034 3494 −2352 550 1334 883
The surface of the Sun 5800 5526 9980 10440 −8140 1823 4421 2909

Normal human body temperature is 36.8 °C ±0.7 °C, or 98.2 °F ±1.3 °F. The commonly given value 98.6 °F is simply the exact conversion of 37 °C, and therefore has excess (invalid) precision. Some numbers in this table have been rounded off.