Basically these three are temperature units.Following are the conversion formulae,

Celsius to Fahrenheit° F = 9/5 × ( ° C) + 32Kelvin to Fahrenheit° F = 9/5(° K - 273) + 32Fahrenheit to Celsius° C = 5/9(° F - 32)Celsius to Kelvin K = ° C + 273Fahrenheit to Kelvin K = 5/9 (° F - 32) + 273

The Kelvin scale is an absolute, thermodynamic scale (meaning twice the number, twice the heat indicated) with the two defining points absolute zero at 0 and the triple point of water at 273.16.

The Celsius temperature is defined to be exactly 273.15 less than the Kelvin temperature. Combining this with the information above about the Kelvin scale yields the two defining points absolute zero at −273,15 and the triple point of water at +0.01. (Contrary to popular belief, the definition of the Celsius scale has nothing to do with the melting point of ice nor the boiling point of water at standard atmospheric pressure.)

The Fahrenheit scale is defined so that the Fahrenheit temperature is 32 more than 1.8 times the Celsius temperature. Combining this with the information above about the Celsius scale yields the two defining points absolute zero at −459.67 and the triple point of water at +32.018. (Contrary to popular belief, the definition of the Fahrenheit scale no longer has anything to do with the melting point of ice and the boiling point of water at standard atmospheric pressure.)