The amplification factor, also called gain , is the extent to which an analog amplifier boosts the strength of a signal . Amplification factors are usually expressed in terms of power . The decibel (dB), a logarithmic unit, is the most common way of quantifying the gain of an amplifier.

In general an amplification factor is the numerical multiplicative factor by which some quantity is increased.

• In structural engineering the amplification factor is the ratio of second order to first order deflections.
• In electronics the amplification factor, or gain, is the ratio of the output to the input of an amplifier, sometimes represented by the symbol A_F.
• In numerical analysis the amplification factor is a number derived using Von Neumann stability analysis to determine stability of a numerical scheme for a partial differential equation.