dB / SPL Calculator
Add and combine decibel levels, convert between dBu, dBV, and dBFS, and calculate SPL at distance using the inverse square law.
Combine dB Levels
Add two or more sound sources (in dB SPL) to find the combined level. Uses logarithmic addition: Ltotal = 10 × log10(∑ 10Li/10).
| Source Label | Level (dB SPL) | Linear Power | |
|---|---|---|---|
| — | |||
| — |
Combined Level
—
Increase over Loudest
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Number of Sources
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SPL at Distance (Inverse Square Law)
Calculate sound pressure level at a given distance from a known reference level and distance. SPL drops by 6 dB per doubling of distance in free field.
dB
m
m
SPL at Target
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Level Drop
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Distance Ratio
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Doublings
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SPL at Multiple Distances
| Distance | SPL | Drop from Reference |
|---|
dB Unit Converter
Convert between dBu, dBV, dBFS, volts (RMS), and watts. Enter any one value to calculate the rest.
ref: 0.775 V RMS
ref: 1.000 V RMS
0 dBFS = +24 dBu (default)
dBu
Adjustable (18–24 typical)
W
Load:
Quick Reference
Common SPL Levels
| Source | dB SPL |
|---|---|
| Threshold of hearing | 0 dB |
| Whisper | 30 dB |
| Normal conversation | 60 dB |
| Busy traffic | 80 dB |
| Front of house mix position | 95–105 dB |
| Rock concert (FOH) | 100–110 dB |
| Threshold of pain | 130 dB |
dB Rules of Thumb
| Change | Perceived Effect |
|---|---|
| +1 dB | Just noticeable increase |
| +3 dB | Double the power (noticeable) |
| +6 dB | Double the voltage / pressure |
| +10 dB | Perceived as "twice as loud" |
| +20 dB | 10× voltage, 100× power |
| −6 dB per doubling of distance | Inverse square law (free field) |