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The common scales for most temperature expressions are Celsius and Fahrenheit, while Kelvin is used for scientific applications.
To calculate degrees Celcius from a known Temperature in degrees Fahrenheit use:
Tc = (5/9)*(Tf-32); Where Tc = temperature in degrees Celsius, Tf = temperature in degrees Fahrenheit
For example, assume you have a Fahrenheit temperature of 98.6 degrees and you desire to convert it into degrees on the Celsius scale. Using the above formula, you would first subtract 32 from the Fahrenheit temperature and get 66.6 as a result. Then you multiply 66.6 by five-ninths and get the converted value of 37 degrees Celsius.
To calculate degrees Fahrenheit from a known Temperature in degrees Celsius use:
Tf = (9/5)*Tc+32; Where Tc = temperature in degrees Celsius, Tf = temperature in degrees Fahrenheit
Assume that you have a Celsius scale temperature of 100 degrees and you wish to convert it into degrees on the Fahrenheit scale. Using the stated formula, you first multiply the Celsius scale temperature reading by nine-fifths and get a result of 180. Then add 32 to 180 and get the final converted result of 212 degrees on the Fahrenheit scale.
The Celsius temperature scale is still sometimes referred to as the "centigrade" scale. Centigrade means "consisting of or divided into 100 degrees;" the Celsius scale, devised by Swedish Astronomer Andres Celsius (1701-1744) for scientific purposes, has 100 degrees between the freezing point of 0 degrees and boiling point of 100 degrees of pure water at sea level air pressure, 29.92 inches of mercury. That pressure criteria is often called an atmosphere, or more commonly, standard pressure. The term Celsius was adopted in 1948 by an international conference on weights and measures. This is the most widely used scale in the world.
On the Fahrenheit scale, used primarily in the United States, the freezing point of water is 32 degrees and the boiling point is 212 degrees while measured at standard pressure. Zero degrees Fahrenheit was the coldest temperature that the German born scientist Gabriel Daniel Fahrenheit could create with a mixture of ice and ordinary salt. He is credited with the invention of the mercury thermometer and introduced it and his scale in 1714 in Holland, where he lived most of his life. His thermometer was based on the original design papers by Galileo for a temperature and pressure measuring device.
Scientists use a third scale for unique measurements, called the absolute or Kelvin scale. This scale was invented by William Thomson, also known as Lord Kelvin, a British scientist who made important discoveries about heat in the 1800's. Scientists have determined that the coldest it can get, in theory, is minus 273.15 degrees Celsius. This temperature has never actually been reached, though scientists have come close. The value, minus 273.15 degrees Celsius, is called absolute zero. At this temperature scientists believe that molecular motion would stop. You can't get any colder than that. The Kelvin scale uses this number as zero. To get other temperatures in the Kelvin scale, you add 273 degrees to the Celsius temperature. Conversion is very straight forward, though, strangely enough, the word degree is not used with the Kelvin scale.
°C: Celsius (centigrade), °F: Fahrenheit, K: Kelvin
| Scale | °C | °F | K |
| Boiling point of water at 1 atmosphere |
100 | 212 | 373.15 |
| Freezing point of water at 1 atmosphere |
0 | 32 | 273.15 |
