Decibel Ratio Calculator
Enter the ratio and choose whether it is a power or amplitude ratio.
Result
How to use
- Enter your values in the fields above.
- Press Calculate to see your result instantly.
- Use the Share button to copy a link to your result.
About this calculator
The decibel is a logarithmic unit for expressing a ratio, and the formula depends on whether the quantity being compared is a power quantity or a field (amplitude) quantity. For power ratios — such as watts of electrical or acoustic power — the conversion is dB = 10 · log10(P2/P1). For amplitude ratios — such as voltage, current, sound pressure or field strength — it is dB = 20 · log10(A2/A1), with the extra factor of two because power is proportional to amplitude squared, so both formulas agree when applied to the same physical change.
This is exactly why audio engineers use 20·log10 for voltage/gain ratios on a mixing console, RF and telecom engineers use 10·log10 for power ratios in a link budget, and acoustic measurements of sound pressure level also use the 20·log10 form. This calculator converts a ratio you enter into decibels using whichever formula matches the type you select, power or amplitude.
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