Decibel is not an absolute level –
It is purely a comparison between two levels, and on its own it cannot be used to measure an absolute level. As a result of this the quantities of dBm and dBW are used:-
dBm – This is a power expressed in decibels relative to one milliwatt.
dBW – This is a power expressed in decibels relative to one watt.
VBR/ Wallis Dudhnath