Absolute temperature

For most temperature work in the laboratory you will be using the Celsius (centigrade) scale. This is based on the temperature of melting ice being defined as 0 °C and that of boiling water being 100 °C (at standard atmospheric pressure).

However, it was discovered that there is an absolute zero of temperature at - 273.15 °C. It is not possible to reduce temperature below this. It seems sensible to have a temperature scale which defines this lowest temperature as zero. This is the absolute temperature scale. The unit of this scale is the Kelvin, named after the physicist Lord Kelvin. The Kelvin is the same size as the degree centigrade, it's just that the scales start at different points. To convert degrees centigrade to Kelvin (approximately) add 273:

temperature ( in Kelvin) = temperature ( in degrees centigrade) + 273

If you are measuring a temperature change, it will be the same in degrees centigrade as it is in Kelvin. Note that it is not degrees Kelvin. Zero degrees centigrade is 273 K and is said as 273 Kelvin.

The following calculator changes temperatures in °C to Kelvin (the nearest integer value):