Difference Between Celsius and Kelvin (With Table)

Celsius and Kelvin both are used as units for the measurement of temperature. They are represented by two different symbols, oC for Celsius and K for Kelvin. Both of these are used at different places and most of the time Celsius is used for general purposes and simple calculations and Kelvin is used in more scientific problems.

Celsius vs Kelvin 

The difference between Celsius and Kelvin is that they both have different starting points, Celsius starts from 0oc whereas the Kelvin scale starts from 273.15 K.  One Celsius is defined as a scale based on the boiling and freezing point of the water whereas one Kelvin is defined as 1/273.15 of the triple point of water of thermodynamic temperature. 

The Celsius scale generally represented by the unit degree Celsius (oC) is a measure of the difference between two temperatures. In simpler words, it is a range of temperature on the centigrade scale. The basis of the scale is usually taken by the boiling and freezing point of the water that is 100oC and 0oC respectively.

The Kelvin scale was developed by William Thomson, 1st Baron Kelvin after whom the scale was named and the symbol was taken as K. 1.380649×10−23J change in thermal energy is brought by some thermodynamic temperature difference which is known as one Kelvin. Kelvin is usually taken as the SI unit of temperature. 

Comparison Table Between Celsius and Kelvin

Parameters of ComparisonCelsius Kelvin
Definition of the termsCelsius scale is defined based on the boiling and freezing point of waterThe value on the Kelvin scale was defined by the triple point which afterwards changed to Boltzmann constant. 
Symbols UsedIt is represented by the use of oC or simply o is also used to report the temperature in CelsiusIt is represented by the symbol K and the symbol degree is not used unlike in all other units.
Difference in pointsThe freezing and boiling points of water are reported as 0oC and 100oC.The freezing and boiling points of water are reported as 273 K and 373 K.
Molecular Motion It does not consider the molecular motions of the particle during the measurement.It considers the aspect of molecular motion while reporting as it works on the formula of kT
Usage of the unitsMostly this scale is used daily for reporting the temperature where an exact digit is not requiredThis scale is used in most of the scientific formulae and calculations due to it being more precise. 
ExamplesMost of the time the temperature of the human body is represented on the Celsius scaleIn scientific calculations like that of kinetic energy where the temperature has to be related to the inside matter

What is Celsius?

Centigrade scale is a measure of temperature that usually gives the temperature in a form of difference from a reference point. It is represented by the symbol oC and is commonly called the Celsius scale. It is based on the boiling and freezing point of water that is 0oC and 100oC and is also related to pressure as the data above is at 1 atm pressure. The scale was named after the Swedish astronomer Anders Celsius who had replaced the previously used Centigrade scale which was named after a Latin combination of words. The words Centum and Gradus meant hundred and steps respectively.

After some time, the scale was redefined by the use of new parameters known as absolute zero which means a temperature at which entropy and enthalpy are maximum and triple point which is the temperature where three states coexist as they were taken as absolute water standards. Centigrade was used as an informal way of saying degree Celsius. 

The above definition made it easy for the scientists to correlate the two scales that is Celsius and Kelvin. The absolute zero was reported as 273.15K and 0.01oC which proved that the change in one unit was equal for both. 

What is Kelvin?

Kelvin is represented by K and taken as the SI unit of temperature due to its definition being more accurate and precise. The scale is named after its developer William Thomson, 1st Baron Kelvin who is a Physicist and Engineer born in Belfast. He wanted to provide a scale that could serve as the absolute thermodynamic scale. 

It is defined as the temperature change which is brought by the 1.380649×10−23J change in thermal energy. It was defined based on the Boltzmann constant after the rejection of the definition related to the triple point. Earlier, it was defined as 1/273.15 of the triple point of water of thermodynamic temperature.

The scale was developed by Lord Kelvin because he wanted a scale that would start at the infinite cold or the absolute zero and for that, he conducted a series of experiments. He also wanted the scale to be in conjugation with the celsius scale which means the unit increase should be the same.

He calculated the absolute zero which was -273oC and was negative reciprocal of 0.00366 which was the accepted coefficient of gas expansion in reference to ice point for a degree change in temperature. Therefore the number was of this significance. 


Main Differences Between Celsius and Kelvin

  1. The Celsius scale was defined on the basis of the boiling and freezing point of water at a specific temperature whereas the Kelvin scale was based on the triple point of water which eventually was described by the use of the Boltzmann constant.
  2. The celsius scale is represented by the use of degree Celsius symbolised as oC and the Kelvin scale is represented by the use of symbol K and the degree symbol is not used unlike most of the units.
  3. There is a difference between the boiling and freezing point of water on both scales. On the Celsius scale, it is 0oC and 100oC whereas on the Kelvin scale it is 273 K and 373 K. 
  4. The Celsius scale neglects the temperature difference due to the presence of the molecular particle. On the other hand, due to being defined by the use of the Boltzmann constant the Kelvin scale keeps the molecular changes in consideration. 
  5. The Celsius scale is usually used in daily life to tell the temperature of the body or weather whereas the Kelvin scale is used more in scientific calculations and formulae. 


The scales have their own importance and can be used interchangeably because of the provision of the formula and also can be associated with each other. It was reported that both the scales have similarities, that is both of their unit changes are equal. Both of the scales are used in conjugation to each other and are preferably the most used scales in the world. They are also used in different aspects of daily life and have differences in the null points. The two scales were redefined over the years to provide a better understanding and easiness in studies. 


  1. https://pubs.acs.org/doi/abs/10.1021/ed076p911 
  2. https://aapt.scitation.org/doi/pdf/10.1119/1.2341110 
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