Inverting Op-Amp Gain Calculator

About this calculator

An inverting operational amplifier circuit uses two resistors — a feedback resistor Rf and an input resistor Rin — to set a precise, predictable voltage gain given by Av = −Rf / Rin, with the negative sign showing that the output is 180 degrees out of phase with the input. Because the gain depends only on this resistor ratio rather than on the op-amp's own (often inconsistent) open-loop gain, the circuit is a workhorse of analog design.

This calculator computes that gain from the two resistor values, reporting both the raw magnitude and the equivalent gain in decibels (20·log10 of the magnitude). It's a foundational calculation for electrical engineers and electronics hobbyists designing amplifier stages, audio circuits, active filters, and signal-conditioning circuits, where choosing the Rf/Rin ratio is the standard way to dial in a specific, repeatable amount of amplification.