 Top Technical Dictionary dBm - logarithmic power unit  # dBm - logarithmic power unit

 dBm – absolute level relative to 1 mW (milliwatt); according to the rules we should use dBmW, however, dBm unit was adopted.
 The unit is commonly used in telecommunications (e.g. access point output power) or used in designing WLAN networks. Expressed in dB, it indicates, how much the power is higher or lower than 1 mW. 0 dB corresponds to 1 mW (milliwatt).
 A commonly used power equation can be used to convert mW into dBm. P(ref) – reference value, in this case 1 mW (milliwatt)
 To simplify, the power equation (dBm) is: ExampleConvert 10 mW into dBm: The following equation can be used to convert dBm to mW: ExampleConvert 20 dBm into mW (milliwatts). Table 1. Converting dBm into mW - wide range

 -30 dBm 0,001 mW -20 dBm 0,01 mW -10 dBm 0,1 mW 0 dBm 1 mW 10 dBm 10 mW 20 dBm 100 mW 30 dBm 1000 mW 40 dBm 10000 mW 50 dBm 100000 mW 60 dBm 1000000 mW 70 dBm 10000000 mW 80 dBm 100000000 mW

Table 2. Converting dBm into mW - detailed range

 14 dBm 25,119 mW 16 dBm 39,811 mW 18 dBm 63,096 mW 20 dBm 100,000 mW 22 dBm 158,489 mW 24 dBm 251,189 mW 26 dBm 398,107 mW 28 dBm 630,957 mW 30 dBm 1000,000 mW

 Power can be easily converted into voltage: dBm into dBµV and dBmV. However, the internal impedance must be known to convert power to voltage. DVB-T, cable or industrial television systems use 75 Ohm impedance. Radio systems use 50 Ohm impedance.
 Equations for those two environments are given below:
 dBmV = 46,9897 + dBm (@ 50 ohm)dBmV = 48,7506 + dBm (@ 75 ohm)
 ExampleConverting 15 dBm into dBmV (for 50 Ohm impedance)
 dBmV = 46,9897 + 15 = 61,9897 dBmV
 dBµV = 60 + dBmV
 dBµV = 106,98 + dBm (@ 50 ohm)dBµV = 108,75 + dBm (@ 75 ohm)
 ExampleConverting 20 dBm into dBµV (for 50 Ohm impedance)
 dBµV = 106,98 + 20 = 126,98 dBµV