Index Signal & AmplificationDecibel Converter

Decibel Converter

Move between dBu, dBV, volts and ratios with a VU meter for company.

Voltage, rms1.23V

Level in dBV+1.78dBV

Peak of a sine1.74V

Meter reading+0.0VU

Voltage ratio×1.995

Power ratio×3.981

VU meter

The scale is nearly linear in voltage, which is why −20 to −10 takes so little room.

Input

Signal leveldBu

0 VU reference

Any ratio in decibelsdB

Converted to plain voltage and power ratios in the last two read-outs.

How it works

A ratio on a log scale

The decibel expresses a ratio of two powers. Because power goes with the square of voltage, the same step has two forms:

L = 10\log_{10}\!\frac{P}{P_0} = 20\log_{10}\!\frac{V}{V_0}\ \ \mathrm{dB}

Handy anchors: +6 dB doubles a voltage, +10 dB is ten times the power, +20 dB is ten times the voltage.

Absolute units

Adding a letter fixes the reference, turning the ratio into a level you can measure:

dBu: referred to 0.7746 V, the voltage that puts 1 mW into 600 Ω.
dBV: referred to 1 V rms.
dBFS: referred to digital full scale; always zero or negative.

V = 0.7746 \times 10^{\,L_{dBu}/20}

L_{dBV} = L_{dBu} - 2.218

Studio and consumer line level

Professional gear aligns 0 VU with +4 dBu (1.228 V). Consumer gear uses −10 dBV (0.316 V). The gap between them is 11.8 dB, which is why a domestic source can look weak on a studio console.