Celsius and Fahrenheit are the most common temperature measurements.
The centigrade temperature scale, more properly known as the Celsius temperature scale, is a scale for measuring temperatures that is based on the behavior of water at normal pressure. This scale is widely used in much of the world to express temperatures, with some resistant countries using the Fahrenheit temperature scale. The Celsius scale is also used as a reference for the Kelvin scale, which is used in the scientific community.
On the Celsius scale, the freezing point of water is set at 0 degrees and the boiling point of water is 100 degrees. The scale is named after Anders Celsius, a Swede who developed one of the first versions of this scale. Somewhat confusingly, early versions of the centigrade temperature scale were inverted, with water freezing at 100 degrees and boiling at 0 degrees. Linnaeus is widely considered to be the first to use 0 as the freezing point.
The scale was widely referred to as the centigrade temperature scale until 1948, when it was changed to “Celsius” to avoid confusion with a unit of measurement also called the centigrade. However, many people continue to use the term “centigrade temperature scale”, especially members of the lay public who are not in the habit of checking General Conference on Weights and Measures procedures. Both uses are widely understood, although scientists might shudder when hearing “centigrade temperature scale”.
The basic concept of the Celsius scale was adapted in the course of the development of the Kelvin scale. The Kelvin temperature scale uses absolute 0, the theoretically coldest possible temperature, as the 0 point, making the freezing point of water 273.15 kelvins (32 degrees Fahrenheit). The 100 point distance between freezing and boiling is kept on the Kelvin scale, so water boils at 373.15 kelvins (212 degrees Fahrenheit). By the way, a kelvin is a unit of measurement, which is why temperatures are given in “kelvins”, not “degrees kelvin”, and by convention, “kelvin” is not capitalized when giving temperature measurements, although it is when discussing the Kelvin scale.
It is not uncommon to find a thermometer that gives measurements in both Fahrenheit and Celsius, for the convenience of converting between the two systems, particularly in the United States. It might be helpful to know that a degree Fahrenheit is 5/9s of a degree Celsius, and the fastest way to approximate Celsius temperatures in Fahrenheit is to double and add 32, although the actual formula is (°C × 1.8) + 32 .