degrees Celsius
Three temperature scales are in common use in science and industry. Two of those scales are SI metric:
The degree Celsius (°C) scale was devised by dividing the range of temperature between the freezing and boiling temperatures of pure water at standard atmospheric conditions (sea level pressure) into 100 equal parts. Temperatures on this scale were at one time known as degrees centigrade, however it is no longer correct to use that terminology. [In 1948 the official name was changed from "centigrade degree" to "Celsius degree" by the 9th General Conference on Weights and Measures (CGPM).]
Remember the following little poem:
30 is hot.
20 is nice.
10 put a coat on,
0 is ice.
The kelvin (K) temperature scale is an extension of the degree Celsius scale down to absolute zero, a hypothetical temperature characterized by a complete absence of heat energy. Temperatures on this scale are called kelvins, NOT degrees kelvin, kelvin is not capitalized, and the symbol (capital K) stands alone with no degree symbol. [In 1967 the new official name "kelvin" and symbol "K" were set by the 13th General Conference on Weights and Measures (CGPM).]
The degree Fahrenheit (°F) non-metric temperature scale was devised and evolved over time so that the freezing and boiling temperatures of water are whole numbers, but not round numbers as in the Celsius temperature scale
Some baseline temperatures in the three temperature scales:
| temperature |
kelvin |
degree Celsius |
degree Fahrenheit |
| symbol |
K |
°C |
°F |
| boiling point of water |
373.15 |
100. |
212. |
| melting point of ice |
273.15 |
0. |
32. |
| absolute zero |
0. |
-273.15 |
-459.67 |
Common temperature comparisons:
| temperature |
degree Celsius |
degree Fahrenheit |
| symbol |
°C |
°F |
| boiling point of water |
100. |
212. |
| average human body temperature |
37. |
98.6 |
| average room temperature |
20. to 25. |
68. to 77. |
| melting point of ice |
0. |
32. |