dB to Volt Formula and Calculator

This tool converts a dB (deciBel) value to a Voltage ratio.

Volt to dB

Formula

V = 10PdB/20

Where

  • V = Vout/Vin or the ratio between the output and input voltage

and

  • PdB = 20*Log10(V)

Example Calculator

For a dB value of 3, the voltage ratio is 1.414.

Additional Notes

PdB represents a ratio between the output voltage from an amplifier to the voltage input to it. In other words it represents the power gain of the amp. It is a unit-less quantity. Many people confuse dB with dBm.

dBm is the dB value of power referenced to 1 mW. There is a voltage equivalent to both the input and output power in dBm (use this tool to convert from dBm to RMS voltage).

Let’s use an example where the Pout = 13 dBm and Pin = 10 dBm. In this case, PdB = 13-10 = 3 dB (using the dBm to dB calculator).

  • 13 dBm = 1 Volt (Vout)
  • 10 dBm = 0.707 Volt (Vin)
  • Vout/Vin = 1.414 which is the same result in this calculator