dB Converter
dBu, dBV, dBFS and volts against a selectable digital reference: European broadcast (−18 dBFS), SMPTE RP 155 (−20 dBFS) or other broadcast (−16 dBFS). Includes a source-combining add dB tool.
Digital reference
Convert
Combine sources
Combined level for incoherent and coherent sources: summing speaker outputs, multiple mics, or any signal combination.
Incoherent = 10 × log10(Σ 10^(dBᵢ/10)). Coherent = 20 × log10(Σ 10^(dBᵢ/20)). Two sources at the same level add +3 dB incoherent, +6 dB coherent.
Professional Reference Levels
| Standard | Level | Voltage | Typical Use |
|---|---|---|---|
| Professional line level | +4 dBu | 1.228 V | Studio, live sound, broadcast |
| Consumer line level | −10 dBV | 0.316 V | Hi-fi, consumer gear |
| Microphone level | −60 to −40 dBu | 0.0008–0.008 V | Dynamic/condenser mics |
| Instrument level | −20 to −10 dBu | 0.078–0.245 V | Guitars, keyboards (passive) |
| Digital full scale | 0 dBFS | — | Maximum digital level |
| European broadcast / Professional recording | −18 dBFS | — | +4 dBu = −18 dBFS |
| SMPTE RP 155 / Post-production | −20 dBFS | — | +4 dBu = −20 dBFS |
| Headroom target (peaks) | −12 to −6 dBFS | — | Leave room for transients |
Why It Matters
Different industries use different digital reference standards, so the same analog voltage produces different dBFS readings. The formulas below show the fixed relationships. Use them to verify conversions or work offline.
dBu = dBV + 2.218
dBV = dBu - 2.218
dBu = 20 × log10(Volts / 0.775)
Volts = 0.775 × 10^(dBu/20)Frequently Asked Questions
What's the difference between dBu and dBV?
dBu references 0.775V (the voltage that delivers 1 mW into 600Ω). dBV references 1V. The difference is always 2.218 dB. Professional gear uses dBu; consumer gear uses dBV. +4 dBu = +1.78 dBV.
Why does 0 dBFS map to different analog levels?
Digital full scale (0 dBFS) is fixed, but the analog level it represents varies by convention. European broadcast convention uses +4 dBu = −18 dBFS. SMPTE RP 155 sets +4 dBu = −20 dBFS (post-production). Yamaha CL/QL uses −20 dBFS. The converter lets you choose the reference that matches your console.
When do I use incoherent vs coherent summing?
Incoherent (uncorrelated) = different mics on different instruments, separate speakers playing different material, uncorrelated noise. Uses 10×log10(Σ10^(dB/10)). Two sources at the same level add +3 dB.
Coherent (in-phase) = the same signal split to multiple amplifiers, identical speakers producing the same waveform. Uses 20×log10(Σ10^(dB/20)). Doubling the number of sources adds +6 dB. This tool calculates both.
What does −18 dBFS = +4 dBu actually mean?
It's a calibration point. When your console meter reads −18 dBFS, the analog output is +4 dBu (1.228V). This gives 18 dB of headroom before digital clipping (0 dBFS). At +4 dBu nominal, peaks can reach +22 dBu before clipping the converter, plenty for transients.
How do I convert dBu to volts?
Volts = 0.775 × 10^(dBu/20). For example, +4 dBu = 0.775 × 10^(0.2) = 1.228 V. Enter a value in dBu and the converter shows the voltage in the results.
What is 0 dBFS in volts?
0 dBFS has no fixed voltage: it depends on the digital reference. With European broadcast (−18 dBFS = +4 dBu), 0 dBFS = 9.76 V. With SMPTE RP 155 (−20 dBFS = +4 dBu), 0 dBFS = 12.28 V. With other broadcast (−16 dBFS = +4 dBu), 0 dBFS = 7.75 V. Select your reference in the dropdown and enter 0 dBFS to see the equivalent voltage.
How does VU relate to dBu and dBFS?
0 VU is typically calibrated to +4 dBu on professional analog gear. In the digital domain, 0 VU = −18 dBFS (European broadcast) or −20 dBFS (SMPTE RP 155). VU is an averaged reading with 300 ms integration; it under-reports transients, so actual peaks may read several dB higher on a peak meter.