What the decibel scale measures
The decibel (dB) is a logarithmic unit used to express the ratio between two power or amplitude values, commonly for sound intensity or signal strength. For a power ratio, dB = 10 × log10(P1/P0); for an amplitude (voltage or pressure) ratio, dB = 20 × log10(A1/A0), since power is proportional to the square of amplitude.
How this calculator works
Choose whether you’re comparing power values or amplitude/voltage values, enter your measured value and a reference value, and the calculator applies the correct logarithmic formula. A result of 0 dB means the two values are equal; positive dB means the value is louder or stronger than the reference, and negative dB means it’s quieter or weaker.
Because decibels are logarithmic, every 10 dB increase represents a 10x increase in power (or about 3.16x in amplitude). This tool is for general educational and planning purposes.