dBm to Volt Calculator

This tool converts Power in dBm to Voltage.

While it’s not explicitly stated, the voltage in this case represents the root-mean-square value or V_RMS.

The default impedance (Z) is 50 ohm, although you can change that to any value.

???? Convert Volt to dBm

Formula

V_RMS = SQRT(Z/1000)*10^(P_dBm/20)

where

• Z is the impedance in ohm (Ω)
• P_dBm is the power in dBm

The RMS voltage is directly proportional to both the impedance and the power.

Sometimes the power is specified in Watt and in that case convert from Watt to dBm before using the calculator.

Background

dBm is a unit of power that stands for deciBel referenced to 1 milliwatt. The equation is used to convert from mW to dBm: P_dBm = 10*log₁₀(P_mW).

The Root Mean Square (RMS) average of a set of numbers is the square root of the arithmetic mean of the squares of the values.

Consider a sequence of voltage amplitudes taken at regular intervals of time: V₁, V₂, … V_n . The RMS voltage is given by the formula:

V_RMS = √(1/n)(V₁² +V₂² + … + V_n²)

Example Calculations

• 1 dBm into a 50 ohm impedance translates to Voltage of 251 millivolt.
• The same power into half the impedance value of 25 ohm gives 177 mV.
• The maximum output from a signal generator is typically +20 dBm. This converts to 2.236 Volt.

As the impedance decreases, the voltage decreases as well.

Applications

dBm to Volt conversion can be used in the following situations:

• A software radio receiver is used to convert a radio frequency signal to base band frequencies where there’s typically an operational amplifier. dBm input can be converted to an equivalent voltage using the calculator.
• The output of an RF signal generator is typically specified in dBm. Inputs to certain circuits might be specified in volts. For example the maximum and input voltage levels. The calculator on this page can be used to find the equivalent voltage levels.

Related Calculators

• Use the calculated voltage to find the peak to peak voltage assuming it’s a sine wave.
• RMS voltage depends on the shape of the waveform. Use this calculator to find V_RMS based on whether it’s a square, triangle or other type of wave.

dBm to Volt Excel Calculator

Use Excel to calculate a range of dBm to RMS Volt values. Use the following formula to calculate the value of voltage

B4 = (SQRT($B$1/1000))*10^(A4/20)

Voltage values are in Column B, while dBm values are in column A. The impedance value is fixed and in Cell B1.

dBm to Volt Conversion Table

This table shows dBm values and their equivalent in Volt.