dBu ⇄ dBV ⇄ Volts Converter

Understanding the dBu, dBV and volts converter — concept and principle

Audio equipment describes signal levels in decibels relative to a reference voltage. Professional gear uses dBu, consumer gear uses dBV, and digital systems use dBFS. Converting a voltage into these units tells you whether two devices are compatible, how much gain or attenuation you need, and how much headroom remains. Enter an RMS voltage to get dBu, dBV and the peak voltage of a sine wave.

The same 1.228 V reads +4 dBu or +1.78 dBV — only the reference voltage differs.

How it is calculated

dBu = 20 × log₁₀(V ÷ 0.7746)
dBV = 20 × log₁₀(V ÷ 1)
Peak voltage (sine) = V × √2

V is the RMS voltage in volts. Because the two references differ by a fixed factor, dBu = dBV + 2.21 dB at every level.

The principle

Decibels express ratios on a logarithmic scale. For voltage, the factor is 20 rather than 10, because power is proportional to voltage squared. The dBu reference, 0.7746 V, is the voltage that dissipates 1 mW in a 600 Ω load (√(0.001 × 600)), a legacy of telephone lines; today it is used regardless of load impedance. dBV simply uses 1 V. For a sine wave the peak is √2 times the RMS value, which matters for clipping, since circuits clip on peaks. dBFS is relative to the largest digital value a converter can represent, so its link to volts depends on each device's calibration; common alignments place 0 dBu at −18 dBFS (EBU R68) or +4 dBu at −20 dBFS (SMPTE RP155).

Worked example

Input: V = 1.228 V RMS.
dBu: 1.228 ÷ 0.7746 = 1.58534; 20 × log₁₀(1.58534) = +4.00 dBu (4.002417483).
dBV: 20 × log₁₀(1.228) = +1.78 dBV (1.783967336).
Peak: 1.228 × 1.41421 = 1.737 V (1.736654255).

Each point is the calculator re-run with only “Voltage (V rms)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Voltage (V rms)	dBu
0.307	-8.038782343
0.614	-2.01818243
0.921	1.503642751
1.23	4.002417483
1.53	5.940617743
1.84	7.524242664
2.46	10.0230174

How to read the result

+4 dBu (1.228 V) is professional line level; −10 dBV (0.316 V) is consumer line level. The two differ by about 11.8 dB, so connecting a consumer output to a professional input needs extra gain, while the reverse risks overload. Microphone signals are far lower, typically tens of decibels below line level. Mixer outputs commonly reach +20 dBu or more before clipping, which gives headroom above nominal level.

Common mistakes

Using 10 × log for voltages; that formula is for power ratios.
Confusing RMS with peak or peak-to-peak voltage readings.
Assuming dBFS has a fixed conversion to dBu; it depends on the converter.

Keep in mind: The peak conversion applies only to pure sine waves; music and speech have higher crest factors. Check equipment manuals for real input limits.

Frequently asked questions

Is dBu the same as dBm?

They match only across a 600 Ω load. dBm measures power (1 mW reference); dBu measures voltage.

Why does the converter not show dBFS?

A dBFS value can only be found once you know the alignment level of your interface or converter, such as −18 dBFS = 0 dBu.

What voltage is 0 dBV?

Exactly 1 V RMS, which is +2.21 dBu.

Sources: G. Ballou (ed.), Handbook for Sound Engineers, Focal Press · EBU Recommendation R68, Alignment level in digital audio production equipment

Checked 8 Nov 2026. Standard textbook formulas in SI units, computed in your browser. For learning and estimates — real designs must follow your local codes and be checked by a qualified engineer.

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