Op-Amp Gain Calculator

About this calculator

This calculator finds closed-loop gain for the two basic op-amp configurations using the ideal op-amp approximation — infinite open-loop gain and input impedance, which forces the two input terminals to sit at the same voltage (a "virtual short"). For the non-inverting configuration, gain is Av = 1 + Rf/Rin; for the inverting configuration, gain is Av = −Rf/Rin, with the negative sign showing the output is 180° out of phase with the input. Both follow from applying Kirchhoff's current law at the inverting input node.

Electronics engineers use these formulas constantly when designing audio preamps, sensor signal-conditioning circuits, and instrumentation amplifiers, since picking two resistor values sets the gain directly without touching the op-amp itself. Hobbyists prototyping analog circuits and electrical engineering students learning feedback theory rely on the same pair of equations to size Rf and Rin for a target gain.