Free to use, no account
Decibel Calculator
Convert ratios to decibels, convert dB back to linear ratios, add uncorrelated levels, or calculate the result of gain and attenuation.
How do I use the decibel calculator?
Choose a calculation. Enter a positive power or amplitude ratio, a dB value, multiple levels (one per line), or an input level and gain. The result and formula appear in your browser.
Frequently asked questions
How do I use the decibel calculator?
Choose a calculation. Enter a positive power or amplitude ratio, a dB value, multiple levels (one per line), or an input level and gain. The result and formula appear in your browser.
Are my values uploaded?
No. Calculations run locally in this browser; values are not uploaded or saved.
What is the difference between a power ratio and an amplitude ratio?
Power ratios use 10 × log10(ratio). Amplitude ratios use 20 × log10(ratio) when both measurements have the same impedance.
Why do two equal sound levels add about 3 dB?
For uncorrelated sources, their powers add; two equal levels therefore increase by about 3.01 dB. Correlated signals need phase-aware calculation.
Can this calculator measure dB SPL with my microphone?
No. It does arithmetic on values you enter. It does not access a microphone, calibrate a sound meter, or measure acoustic pressure.