How to use the audio level unit converter
- Enter a level and pick its unit: dBu, dBV, volts RMS, volts peak, volts peak-to-peak or dBm.
- For dBm, set the load impedance. 600 ohms is the classic audio value.
- Read the same level in every unit, with the power into the load.
- Compare with the table of common line levels.
Formula
dBu = 20 log10(V / 0.7746), the reference being sqrt(0.6) volts RMS
dBV = 20 log10(V / 1 volt RMS)
dBm = 10 log10(power in mW), power = V^2 / load
Peak = RMS x 1.4142; peak-to-peak = 2 x peak (sine wave)
The dBu reference is the voltage that puts 1 mW into 600 ohms. dBu and dBV differ by a fixed 2.2185 dB.
Professional and consumer line levels
A level of +4 dBu is 1.22765 volts RMS, which is 1.782 dBV, 1.73616 volts peak and 3.47233 volts peak-to-peak, and delivers 2.5119 mW into 600 ohms. A level of -10 dBV is 0.31623 volts RMS, which is -7.782 dBu.
One volt RMS is 2.218 dBu and 0 dBV, and gives 1.6667 mW into 600 ohms. A signal of 0 dBm into 600 ohms is 0.7746 volts RMS, which is 0 dBu and -2.218 dBV.
Why so many units
Decibels compare a level to a reference, and audio uses several. dBV uses one volt, popular in consumer gear, and dBu uses the 0.7746 volt value inherited from telephone lines and used in professional equipment. dBm is a power level, so it needs the load that the power is delivered into, while the others describe only voltage.
For ratios of power and sound pressure see the decibel calculator. Related audio tools include the note frequency converter, the audio buffer latency calculator and the Ohm's law calculator.
Peak and peak-to-peak
Voltage is usually quoted as RMS, which is the steady value with the same heating effect. For a pure sine wave the peak is 1.4142 times larger and the swing from lowest to highest is twice the peak. Music and speech have much higher peaks compared with their RMS level, so those two conversions apply to sine waves only.
Assumptions and limits
- Peak and peak-to-peak conversions assume a sine wave.
- dBm and power use the load impedance you enter, 600 ohms by default as an example.
- The 2.2185 dB offset between dBu and dBV is exact for the standard references.
- Levels from -400 to 400 dB are accepted; the result must fit within the range the page can show.
Frequently asked questions
What is the difference between dBu and dBV?
dBV is referenced to 1 volt RMS and dBu to 0.7746 volts RMS. Because of that, a level in dBu is always 2.218 dB higher than the same level in dBV.
What is +4 dBu?
It is the nominal professional line level, 1.228 volts RMS. The matching consumer level is -10 dBV, which is 0.316 volts RMS, so professional gear runs about 11.8 dB hotter.
When does dBm equal dBu?
Only when the load is 600 ohms, because the dBu reference is the voltage that gives 1 mW into 600 ohms. For other loads the two differ by a fixed amount.
Can I convert dB to volts?
Yes. Enter the level in dBu or dBV and read the volts RMS. The relation is volts = reference x 10^(dB / 20).