Decibel Voltage Ratio Calculator

Turn a voltage ratio into decibels (dB).

How to use

  1. Enter your values in the fields above.
  2. Press Calculate to see your result instantly.
  3. Use the Share button to copy a link to your result.

About this calculator

This calculator uses the field-quantity decibel formula, dB = 20 × log₁₀(Vout / Vin), which differs from the power-ratio formula (10 × log₁₀) by a factor of two because power is proportional to voltage squared. A ratio of exactly 2 (doubling the voltage) works out to about +6.02 dB, and a ratio of 10 works out to exactly +20 dB.

Audio engineers use it to read gain and attenuation straight off an amplifier's or mixer's voltage figures, electronics designers use it to spec op-amp and filter circuits in datasheets, and it's the same math behind the dB markings on volume knobs and equalizer sliders.

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