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Op-Amp Gain Calculator (Inverting & Non-Inverting)

Calculate an ideal op-amp circuit's closed-loop gain and output voltage for the standard inverting (Av = -Rf/Rin) or non-inverting (Av = 1 + Rf/Rin) feedback topology, plus the gain in dB.

Closed-loop gain (Av)
-10×
Gain in dB
20 dB
Output voltage (Vout)
-10 V

How it works

An ideal op-amp (infinite open-loop gain, infinite input impedance) wired with a single feedback resistor Rf and input resistor Rin gives one of two standard closed-loop gains depending on which input the signal drives: inverting, Av = -Rf ÷ Rin (output 180° out of phase, and the magnitude can be less than 1), or non-inverting, Av = 1 + Rf ÷ Rin (output in phase, and the magnitude is always at least 1 since it can't attenuate). Either way, the output voltage is simply Vout = Av × Vin.

The same gain is also reported in decibels, 20·log₁₀|Av| — the units an op-amp datasheet or Bode plot almost always uses instead of a raw ratio, which makes it easy to cross-reference against a chip's own gain-bandwidth-product specification.

Rf and Rin are entered in kilohms as abstract electrical quantities (like this site's Ohm's Law and RC Time Constant calculators), not physical measurements, so there's no metric/imperial toggle — only the resistor ratio matters, not the absolute resistance values.

FAQ

Why is the inverting gain negative, and does that matter for the magnitude?

The negative sign means the output is 180° out of phase with the input — when the input swings positive, the output swings negative by the same scaled amount. For sizing purposes (how much the signal gets amplified), only the magnitude |Av| = Rf/Rin matters; the sign just tells you the output is flipped, which this calculator preserves in the raw gain figure so you can see both at once.

Can the non-inverting gain ever be less than 1?

No — Av = 1 + Rf/Rin is always at least 1, since Rf/Rin can't go negative with positive resistors. If you need a gain below 1 (attenuation) in phase with the input, a non-inverting op-amp stage can't do it alone; you'd need a separate resistive divider ahead of it, or use the inverting topology instead, which can produce any ratio including less than 1.

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