Op-Amp Gain Calculator

Gain equals minus the feedback resistor over the input resistor, gain = -Rf / Rin. With Rin = 1k and Rf = 10k the gain is -10, and the decibel figure uses the magnitude, so 20 dB.

Gain equals 1 plus the feedback resistor over the input resistor, gain = 1 + Rf / Rin. Because of the added 1, a non-inverting stage can never go below unity gain, and the minimum is exactly 1.

The output swings opposite to the input, 180 degrees out of phase, so the gain carries a minus sign. The magnitude is still Rf over Rin, which is what sets the decibel value.

Gain in decibels is 20 times the base-10 logarithm of the gain magnitude, 20 * log10(|gain|). A gain of 10 is exactly 20 dB, a gain of 11 is about 20.83 dB, and a gain of 1 (unity) is 0 dB.

Yes. Each resistor has its own unit selector, so you can enter Rin in k ohm and Rf in M ohm. The tool converts both to ohms before dividing, and only the ratio matters, not the absolute values.

Yes. It uses the ideal closed-loop equations and ignores finite open-loop gain, gain-bandwidth product, slew rate and input offsets, which is accurate for most low-frequency, moderate-gain designs.

Use the inverting topology, where any Rf smaller than Rin gives a magnitude under 1 (attenuation). The non-inverting topology cannot attenuate because of the 1 plus Rf over Rin term.

No. The math runs locally in your browser, so your resistor values are never uploaded or stored. The page keeps working offline once it has loaded.

For the surrounding design, see the voltage divider calculator for reference and bias networks, the Ohm's law calculator for currents, and the RC time constant calculator for filter corners.