Decibel (dB) Calculator

Decibels are defined as ten times the log of a power ratio or twenty times the log of Voltage Ratio.

dB = 20log10(V1/V2) = 10log10(P1/P2)


Enter either Power Gain (P1/P2) or Voltage gain to calculate the Decibel (dB).






You can also use this calculator to find out the Power Gain and Voltage Gain from the Decibel value. Just enter the Decibel value and leave Power Gain & Voltage Gain blank, and then hit the Calculate button.


dBm Calculator:

As we know Decibel in dB can be calculated as:

dB= 20log(V1/V2)= 10log(P1/P2)

If we put P2 = 1mW = .001 watt  then it becomes dBm:

dBm= 10log(p1/.001)

Means dBm is calculated when the input power is considered as 1mW