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Decibel ratio calculator

Convert a power or amplitude ratio into a level difference and see which logarithm rule applies.

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01

Your inputs

The starting values are an example.

Decimals: 12.5 · Thousands: 1,234.56. Follow the field instructions for lists.

02

Your result

Enter your values and select Calculate.

Your calculation will appear here.

Your result will include the relevant values and units.

Understand the calculation

Formula and example

How it is calculated

Power: ΔL = 10 × log₁₀(P₂/P₁); amplitude: ΔL = 20 × log₁₀(A₂/A₁)

Worked example

Doubling the power gives approximately +3.01 dB. Doubling the amplitude at equal impedance gives approximately +6.02 dB.

Things to check

  • The result is a relative level difference. An absolute sound pressure level also requires a defined reference value.
  • The 20-log rule applies to amplitudes only when power is proportional to the square of the amplitude being compared.

Sources and references