In case of reference-related dBs, dB is defined as 10∙log(P/Pref) or 20∙log(V/Vref). In the table below you find the most commonly used dBs.
| dBV | Vref = 1VRMS | dBV = 20∙log(V/1VRMS) |
| dBW | Pref = 1W | dBW = 10∙log(P/1W) |
| dBj | Vref = 1mVRMS | dBj = 20∙log(V/1mVRMS) |
| dBm | Pref = 1mW | dBm = 10∙log(P/1mW) |
| dBu (=dBv) | Vref = √0.6V = 0.775VRMS (0.6V is the voltage across a 600 ohm resistor dissipating 1mW) | dBu = 20∙log(V/0.775VRMS) |
Examples: 0dBV = 1V = 60dBj; 0dBW = 1W = 30dBm.