The primary difference between the centigrade, or Celsius, scale and the absolute, or Kelvin, scale is in their respective starting points. The Celsius scale sets the freezing point of pure water at sea level as 0, while 0 degrees Kelvin is absolute zero, the coldest temperature theoretically possible.
For conversion, 0 degrees Kelvin is -273.15 degrees Celsius. Unlike temperature changes measured with the non-metric Fahrenheit scale, a 1-degree rise on the Celsius scale is identical to a 1-degree rise on the Kelvin scale.
The Kelvin scale is primarily seen in precise or academic measurements relating to the physical sciences. It is generally used in coordination with Celsius.