Op-Amp Gain Calculator

About this tool

Calculate the voltage gain of a basic inverting or non-inverting op-amp amplifier from its feedback and input resistor values, assuming an ideal op-amp — plus the resulting output voltage if you enter an input voltage.

Frequently asked questions

What are the gain formulas?

Inverting: Gain = −Rf / Rin (output is inverted relative to input). Non-inverting: Gain = 1 + Rf / Rin (output is in phase with input and always at least 1).

Why does this assume an "ideal" op-amp?

Real op-amps have finite open-loop gain, bandwidth, input bias current, and slew rate that can limit accuracy at high frequencies or gains — this calculator gives the textbook DC/low-frequency gain, which is a very close approximation for most general-purpose op-amps in typical use.

Can Rin be zero in the non-inverting configuration?

Yes — an infinite (open) or very large Rin with a feedback resistor still connected gives a gain approaching 1 (a unity-gain buffer); this tool treats an empty Rin as a voltage follower where gain = 1.