Celsius, or centigrade, is a temperature scale in the metric system. The scale was originally defined such that at standard atmospheric pressure water freezes at 0 ºC and boils at 100 ºC. To convert from Fahrenheit to Celsius take the Fahrenheit temperature, subtract 32 then multiply by 5 and divide by 9.
One Celsius degree is equal to one Kelvin, with an offset such that T(°C) = T(K) - 273,15
Celsius is the commonly used unit of temperature in Europe, but in the United States, Fahrenheit is still preferred.