Volt to dBu Calculator

This tool converts RMS Voltage to dBu.

In what follows we also provide an overview of what dBu and RMS voltage mean.

Formula

dBu = 20*Log₁₀(V_RMS/0.7746)

dBu is the RMS voltage relative to 0.7746 Volt.

1 V_RMS is therefore equivalent to 20*Log₁₀(1/0.7746) = 2.218 dBu

The inverse relationship or conversion from dBu to V_RMS is defined by the formula V_RMS = 10^{(dBu / 20)} x 0.7746.

Notes:

dBu is different from dBV which is the RMS voltage relative to 1 Volt. dBV to dBm Calculator.
dBu is also not the same as dBuV or dBµV which is the RMS voltage relative to 1 microvolt. dBµV to dBm Calculator.

Where does the number 0.7746 come from?

It is the value of voltage that dissipates 1 milliwatt (mW) into a 600 ohm load. Reference: Wikipedia article on dB Voltage

V = √(600Ω * 0.001W) Volt = 0.7746 V

dBu was originally dBv, however it was changed to what it is today to avoid confusion with dBV. Wikipedia Reference.

The Root mean square (RMS) voltage is the square root of the arithmetic mean of the squares of a set of voltage values.

RMS Value Formula

The formula for this is

V_RMS = √(1/n)(V₁² + V₂² + … + V_n²)

where V_RMS is the RMS value of the sequence of numbers V₁, V₂ … V_n.

Use the following calculators to find VRMS from