Celcius

Celsius is a widely used temperature scale named after the Swedish astronomer Anders Celsius. Proposed in 1742 as a centigrade scale, it originally ran from 0 to 100 with the points defined by water’s freezing and boiling under standard conditions. The scale was later reversed to its current form and ultimately named Celsius. The spelling Celcius is a common misspelling found in informal use.

In the conventional definition, 0 degrees Celsius is the freezing point of water at standard atmospheric pressure, and 100 degrees Celsius is the boiling point of water at the same pressure. These fixed points make the scale convenient for everyday use and for calibration of thermometers. The Celsius scale is a component of the metric system and is used in most of the world for weather, education, healthcare, and many engineering fields.

Notation and usage: The unit is written as the degree Celsius (symbol °C). Temperature differences are measured in the same size of unit as kelvin, so a change of 1 °C equals a change of 1 kelvin. In scientific contexts, the Celsius scale is typically used alongside the kelvin, with the relation T(K) = T(°C) + 273.15.

Conversions: To convert to Fahrenheit, C = (F − 32) × 5/9; to convert from Celsius, F = C × 9/5 + 32. The kelvin scale relates by K = C + 273.15. Celsius remains the standard for everyday temperature measurement in most countries.