RF Power to Voltage Calculator

This tool converts Radio Frequency Power to Voltage – both RMS and Peak.

Enter:

• Power with units specified in Watt or dBm
• Impedance

Formula

If Power is expressed in Watt,

VRMS = √(PWatt * Z)

If Power is expressed in dBm,

VRMS = SQRT(Z/1000)*10(PdBm/20)

The peak-to-peak voltage is calculated using the formula:

VPP = (2√2)*VRMS

Peak voltage can be calculated from the Peak-to-peak voltage:

VP = VPP/2

Background

What is dBm?

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

What is RMS Voltage?

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, … Vn . The RMS voltage is given by the formula:

VRMS = √(1/n)(V12 +V22 + … + Vn2)

What is Peak Voltage?

Peak voltage refers to the maximum instantaneous voltage in an electrical waveform. It represents the highest voltage level reached during one complete cycle of an alternating current (AC) waveform or a transient voltage event. Peak voltage is often used to describe the amplitude of voltage variations in electrical signals.

In the picture below,

1. Peak (or amplitude),
2. Peak-to-Peak,

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 in a 50 ohm system.

As the impedance decreases, the voltage decreases as well.

Applications

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

• The output from an analog Radio Frequency system is usually specified in dBm. This might be input to an analog-to-digital converter that converts a voltage level to equivalent bits.
• The output of an RF signal generator is in dBm. Input range by way of max and min levels to certain circuits might be specified in volts. Use the calculator to convert from dBm to Volt.