A decibel watt is a unit of measurement for the strength of a signal expressed in decibels relative to one watt. It is used because it can express both very large and very small values of power in a short range of numbers.; e.g., 1 milliwatt = −30 dBW, 1 watt = 0 dBW, 10 watts = 10 dBW, 100 watts = 20 dBW, and 1,000,000 W = 60 dBW.