Calculate dBu or voltage from the other value with this dBu voltage calculator for audio signal levels, using the 0.775 V reference.
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Dbu Voltage Formula
The dBu voltage conversion is based on a 0.775 volt reference. A dBu value tells you how many decibels a voltage is above or below 0.775 V RMS.
- dBu = voltage level in decibels relative to 0.775 V
- V = voltage in volts RMS
- 0.775 = the reference voltage for dBu, in volts RMS
- log10 = base-10 logarithm
If you enter voltage, the calculator uses the logarithmic formula to find dBu. If you enter dBu, it rearranges the formula to solve for voltage. Because dBu is a ratio-based unit, equal dBu changes represent proportional voltage changes rather than simple linear changes.
Common dBu to Voltage Reference Values
Use these common values to compare your result against typical audio voltage levels.
| dBu | Voltage RMS | Common meaning |
|---|---|---|
| -10 dBu | 0.245 V | Lower consumer or instrument-level signal range |
| 0 dBu | 0.775 V | dBu reference level |
| +4 dBu | 1.228 V | Common professional line level |
| +10 dBu | 2.451 V | Higher line-level signal |
| +20 dBu | 7.750 V | Very high audio signal level |
Voltage Change by dBu Difference
A dBu increase changes voltage by a ratio. This table shows common dBu differences and the matching voltage multiplier.
| dBu change | Voltage multiplier | Meaning |
|---|---|---|
| +3 dB | 1.413x | Voltage increases by about 41% |
| +6 dB | 1.995x | Voltage is about doubled |
| +10 dB | 3.162x | Voltage is a little over tripled |
| +20 dB | 10x | Voltage is multiplied by 10 |
Example Calculations
Example 1: Convert voltage to dBu
Suppose the voltage is 1.228 V.
The result is about +4.00 dBu.
Example 2: Convert dBu to voltage
Suppose the level is +10 dBu.
The result is about 2.451 V RMS.
FAQ
What does 0 dBu mean?
0 dBu means the voltage is exactly 0.775 V RMS. Positive dBu values are above 0.775 V, and negative dBu values are below 0.775 V.
Is dBu the same as dBV?
No. dBu uses 0.775 V as its reference, while dBV uses 1.000 V as its reference. The same voltage will have different dBu and dBV values because the reference levels are different.
Why does the formula use 20 instead of 10?
The dBu formula uses 20 because it is comparing voltage ratios. Decibel formulas for power ratios use 10, but voltage and amplitude ratios use 20 when the impedance relationship is assumed to be consistent.