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

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.

References

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