The decibel is a standard unit for measuring relative levels of current, voltage, or power.

The decibel shows the ratio between the input and the output.

Decibel is abbreviated dB.

A minus sign before the dB indicates a loss and a plus sign or no sign at all before the dB indicates a gain.

The Decibel Formula

The decibel value of a change between input and output can be expressed utilizing the following algorithm:

db = log10 Input / Output

A Decibel Table

Decibel Gain Ratio of Gain
1 1.3
3 2.0
5 3.2
6 4.0
7 5.0
10 10
20 100
30 1,000
40 10,000
50 100,000
60 1,000,000

From this table, we can see that a gain of 3dB doubles the signal. Similarly, a loss of -3dB reduces the signal strength by half.