Celsius, historically known as centigrade, is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius (1701–1744). 0 °C was defined as the freezing point of water and 100 °C was defined as the boiling point of water.
In 1742, Swedish astronomer Anders Celsius (1701–1744) created a temperature scale that was the reverse of the scale now known as "Celsius": 0 represented the boiling point of water, while 100 represented the freezing point of water. He recounted his experiments showing that the melting point of ice is essentially unaffected by pressure. He also determined with remarkable precision how the boiling point of water varied as a function of atmospheric pressure. He proposed that the zero point of his temperature scale, being the boiling point, would be calibrated at the mean barometric pressure at mean sea level. This pressure is known as one standard atmosphere.
it is sometimes called the centigrade scale because of the 100-degree interval between the defined points.
The following formula can be used to convert a temperature from its representation on the Fahrenheit (°F) scale to the Celsius (°C) value: °C = 5/9(°F − 32)
The Celsius scale is in general use wherever the metric system of units has been adopted, and it is used in scientific work everywhere.