Decibel (dB) Calculator
dB (power): 10·log10(P1/P0)
3.0103 dB
dB (voltage): 20·log10(V1/V0)
6.0206 dB
Sum sound levels (dB SPL)
Total dB
64.7712 dB
Perception
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FAQ
Logarithms and dB
Why ×10 for power, ×20 for voltage?
Because P ∝ V². Substituting in 10·log10(P1/P0) gives 10·log10(V1²/V0²) = 20·log10(V1/V0). Same physical quantity expressed in dB.
How to sum decibels?
Do NOT add directly. Convert each dB to linear (10^(dB/10)), sum, convert back: dB_tot = 10·log10(Σ 10^(dBi/10)). Two equal sources only add +3 dB!
How is a power ratio turned into decibels?
A power ratio becomes decibels with 10 log10(P1/P0). For a voltage ratio the formula is 20 log10(V1/V0), because power grows with the square of voltage.
Can two decibel values simply be added?
Decibels do not add directly. Each level goes back to linear scale with 10^(dB/10), the values are summed and the total returns to decibels: two equal sources give only 3 dB more.
What does the dB SPL total mean?
The dB SPL total is the sound level of all the sources together. The calculator pairs it with a reference for perception, from silence through conversation up to the threshold of pain.