Power is simply the amount of energy flowing in time; typical units are Joules per second [J.s-1]. This is also commonly expressed as the equivalent unit, Watts [W]. Here various orders of magnitude are often considered:

microwatt            [µW]            = 10-6            [W]

milliwatt               [mW]            = 10-3           [W]

kilowatt                [kW]            = 103             [W]

megawatt            [MW]            = 106            [W]

The linear power scale of [mW] is often encountered expressed in a logarithmic decibel scale relative to 1mW power [dBm]. The conversion is achieved with the expressions below:


It is worth noting the subtleties of a decibel scale when dealing with [dBm] units. Adding will have the effect of multiplying the linear power. For example 3dB is two times 0dB, and 6dB is four times as much power as 0dB. Absorption of 3dB/m implies that in one meter the power is reduced by half, and after another meter it will be reduced by half again, to one quarter.


Related Terms: Decibel Scales, Energy, Power, Power Density