Converting Power (dBm) To Milliwatts

A decibel is a measurement that expresses a power ratio, rather than an absolute number. One advantage of using decibels to express power instead of milliwatts is that decibels allow attenuation to be expressed as whole numbers. Milliwatts, on the other hand, would typically be expressed as fractions, which are more cumbersome. For example, 13 dBm = 19.953 milliwatts. This advantage is clearly shown on the chart below.