Op-Amp Gain Calculator
Inverting and non-inverting gain from Rf and Rg, in ratio and dB — with noise gain and real-op-amp caveats.
Real-op-amp checks before trusting the ideal math: bandwidth shrinks to GBW/noise-gain; input bias current through big resistors creates offset (keep Rf below ~1 MΩ for bipolar parts); and the inverting input is a virtual ground only while the output isn't railed. The inverting topology's input impedance is just Rin — buffer high-impedance sources first.
Op-Amp Gain Calculator computes closed-loop gain of inverting and non-inverting amplifiers — free, instant and private in your browser. Analog beginners and engineers double-checking gain stages use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About Op-Amp Gain Calculator
Op-Amp Gain Calculator computes closed-loop gain of inverting and non-inverting amplifiers using the standard engineering relation: non-inverting: G = 1 + Rf/Rg; inverting: G = −Rf/Rin; noise gain always 1 + Rf/Rg. Worked live: Rf 100 kΩ over Rg 10 kΩ is ×11 non-inverting (20.8 dB) or ×−10 inverting. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use Op-Amp Gain Calculator
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use Op-Amp Gain Calculator?
- ✓Implements the real formula — non-inverting: G = 1 + Rf/Rg — with the substitution shown, not a black box
- ✓Built for analog beginners and engineers double-checking gain stages
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate op-amp gain?+
Closed-loop gain of inverting and non-inverting amplifiers follows non-inverting: G = 1 + Rf/Rg; inverting: G = −Rf/Rin; noise gain always 1 + Rf/Rg. For example, Rf 100 kΩ over Rg 10 kΩ is ×11 non-inverting (20.8 dB) or ×−10 inverting. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Inverting or non-inverting — which topology should I pick?+
Non-inverting for high input impedance and no phase flip; inverting for summing nodes, defined input impedance (= Rin), gains below 1, and better behaviour with capacitive sources. Noise gain — which sets bandwidth and stability — is 1 + Rf/Rg either way.
How large can I make the feedback resistors?+
Past ~1 MΩ three gremlins grow: bias-current offset (Ib × Rf), Johnson noise (√4kTR), and a pole from Rf against stray capacitance that can ring. Scale both resistors down to keep the ratio; FET-input op-amps tolerate higher values.
Is the Op-Amp Gain Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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