dB Converter
Convert between dB and linear ratio for power (10·log₁₀) or voltage/amplitude (20·log₁₀), and between dB and nepers (1 Np = 8.686 dB). The decibel, demystified.
dB ↔ nepers
Both are logarithmic scales: 1 Np = 8.6859 dB. The neper uses
ln on the amplitude ratio; the dB uses log₁₀.
Quick reference (by quantity)
| dB | Ratio power | Nepers | Meaning |
|---|
How it is computed · dB, ratio and nepers
1. For power (P, in W or mW):
dB = 10·log₁₀(P₂/P₁) and ratio = 10^(dB/10).
That is why ×2 = 3.01 dB and ×10 = 10 dB.
2. For voltage/amplitude (V, A, pressure):
dB = 20·log₁₀(V₂/V₁) and ratio = 10^(dB/20).
Power scales with the square of voltage, hence the factor of 20.
×2 = 6.02 dB and ×10 = 20 dB.
3. The neper is the natural-log equivalent:
Np = ln(amplitude ratio). The fixed conversion is
1 Np = 8.685889638 dB, so dB = Np × 8.6859.
4. Rule of thumb: for power, +3 dB ≈ double and −3 dB ≈ half; +10 dB = ×10.
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