Decibel (dB) converter for dB to magnitude conversion and multiplication of dB  by a number. Formulas for decibel to field and power ratio conversions and multiplication of decibel by a number are given in this page.

Decibel (dB) Converter:

dB - Ratio conversion
Magnitude type
 Conversion type
Ratio (factor) Decibel
 Multiplication by a number (n * B(dB) = A(dB))
Magnitude Type n B  (dB) A (dB)

Note: Use dot "." as decimal separator.


Decibel (dB): Decibel is a unit used to express relative difference in power or intensity, usually between two acoustic or electric signals, equal to ten times the common logarithm of the ratio of the two levels.

Examples to power quantities: Sound power measurements, power spectral density random vibration.

Examples to field quantities:  Voltage, displacement, velocity, acceleration, force, sound pressure, strain.

Reference  acoustic sound pressure level dB(SPL) : The lowest sound pressure which is usually considered the threshold of human hearing (at 1 kHz) is approximately 2*10-5Pa .

List of Equations:

The power relationship in dB power ratio in dB = 10log10 P/P0
The field relationship in dB field ratio in dB = 20log10 A/A0
Multiplication by a number n for power relationship LA (dB) = LB(dB)+10log10n
Multiplication by a number n for field relationship LA (dB) = LB(dB)+20log10n


If P is greater than P0 then ratio is positive; if P is less than P0 then ratio is negative.

P is the measured power and P0 is the reference power.

A is the measured amplitude and A0 is the reference amplitude.

For addition and subtraction operation, LA ≥ LB condition shall be met.