When measuring signal strength, dBm is commonly used and 0 dBm corresponds to 1 mW...

dBm is a unit of power that measures the ratio of a given power level to 1 mW. The formula to convert dBm to mW is: P(mW) = 1mW * 10^(P(dBm)/10). Therefore, -20 dBm corresponds to 0.01 mW, as follows: P(mW) = 1mW * 10^(-20/10) = 0.01 mW References:https://www.rapidtables.com/convert/power/dBm_to_mW.html

The dBm is a logarithmic unit of power relative to 1 milliwatt (mW). -20 dBm means that the signal strength is 20 decibels lower than 1 mW. In terms of mW, this is 0.01 mW. Each 10 dB decrease represents a tenfold decrease in power. Therefore, -20 dBm is10−210−2or 0.01 mW.