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Decibel (dB) Converter

Convert decibels (dB) to power and voltage ratios and back. Includes a quick reference table for 0, 3, 6, 10, 20, 40 dB and more.

Input

dB

Result

Voltage ratio (amplitude)

10×

Power ratio 100×

dBPower ratio (10log₁₀)Voltage ratio (20log₁₀)
0 dB1×1×
1 dB1.2589×1.122×
3 dB1.9953×1.4125×
6 dB3.9811×1.9953×
10 dB10×3.1623×
20 dB100×10×
30 dB1,000×31.6228×
40 dB10,000×100×
60 dB1,000,000×1,000×
80 dB100,000,000×10,000×
100 dB1.000e+10×100,000×

How it works

  • A decibel (dB) is a logarithmic unit that expresses the ratio between two quantities. Power ratios use dB = 10×log₁₀(P2/P1), while amplitude quantities such as voltage, current, or sound pressure use dB = 20×log₁₀(V2/V1).
  • To convert the other way, recover the factor with 10^(dB/10) for power and 10^(dB/20) for voltage. Note that the same dB value yields different factors for power and voltage.
  • As rough benchmarks: 3 dB is about 2× in power, 6 dB is about 2× in voltage, 10 dB is 10× in power, and 20 dB is 10× in voltage. At 40 dB the voltage ratio is 100×.
  • In "Ratio → dB" mode, first choose whether the quantity is power (such as power consumption or signal power) or an amplitude quantity (voltage, current, sound pressure), then enter the factor. The formula switches with your choice.
  • The ratio must be a positive value; values of 0 or below, or empty input, are not calculated. Extremely large or small results are shown in exponential notation.
  • Use it as a quick check for amplifier gain and attenuation, filter response, signal-to-noise ratio, sound pressure level comparisons, and other logarithmic figures. Always confirm real-world ratings against each device's specifications.