It is used because of its capability to express both very large and very small values of power in a short range of number; 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. Compare dBW to dBm, which is referenced to one milliwatt (0.001 W).
Unit conversions A power level of 0 dBm corresponds to a power of 1 milliwatt. A 10 dB increase in level is equivalent to a 10-fold increase in power. Therefore, a 20 dB increase in level is equivalent to a 100-fold increase in power.