dBm to dBV Conversion Calculator

This tool converts from dBm (dB-milliwatt) to dBV (dB-Volt).

Calculator

Enter the dBm (power) value and the impedance and it will compute the equivalent value in dBV

Note:

• The default impedance is 50 ohm although it can be changed to any value.
• Volt is a Root-mean-square (RMS) quantity

🔁 dBV to dBm

Formula

dBV = dBm + 10*Log₁₀(Z) – 30

where Z is the impedance

Background

What is dBm?

dBm stands for deciBel referenced to one milliwatt.

It is commonly used by RF engineers in the context of absolute power levels associated with various components such as filters, amplifiers, splitters and more.

Mathematically it is defined as

P_dBm = 10*log₁₀(P_mW)

where

• P_mW is the power expressed in milliwatt.
• P_dBm is the power expressed in dBm

People often confuse dBm with dB. dB or deciBel has no units and represents the logarithm of a power or amplitude ratio.

Watt is a unit of power or radiant flux. It is equivalent to 1 joule per second or 1 kg⋅m²⋅s⁻³

Note: Watt is a unit of power in the International System of Units (SI). dBm however is not in the International System of Units.

What is dBV?

dBV stands for deciBel relative to 1 Volt.

Mathematically it is expressed as: dBV = 20*Log₁₀(V_RMS/1V)

Note: this is 1 Volt RMS (Root-mean-square*) and not average, peak or peak-to-peak.

Using the formula above or the V to dBV converter: 1 Volt is equivalent to 0 dBV and 2 Volt is equivalent to 6.02 dBV.

Based on the definition of RMS voltage below, we can see that it is a positive quantity greater than or equal to zero.

V_RMS = √(1/n)(V₁² +V₂² + … + V_n²)

For values of V_RMS greater than 1, the equivalent value of dBV will be positive. If V_RMS is less than 1, the equivalent dBV will be negative.

The exception is V_RMS=0 where the equivalent dBV is infinitesimally small or -∞.

Note there is no reliance on impedance or resistance in the conversion formula.