Milliwatts to dbm conversion

The 'm' in dBm means the power is referenced to 1mW. So, the power in dBm equals 10 times the log of the power in mW, or P(dBm) = 10*log(P(mW)/1mW). For example, 1W = 1000mW, so 10*log(1000/1) = 30dBm.