GlenCalc

Decibel calculator

Decibels compare two levels on a log scale: +3 dB doubles power, +10 dB is ten times.

Your answer

Decibels3 dB
Power ratio1.9953 ×
Voltage (amplitude) ratio1.4125 ×

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How we worked it out

Updated as you change the numbers.

  1. dB = 10 log₁₀(power ratio) = 20 log₁₀(voltage ratio). dBm = 10 log₁₀(power in mW).

Method and assumptions

Power ratios use 10 log, amplitude (voltage, current, sound pressure) ratios use 20 log, because power goes with the square of amplitude.

Questions

How many watts is 30 dBm?

1 W.

Sources

Method and figures checked on . Every worked answer on this page is covered by an automated test. Found a mistake? Tell us.

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