Op-Amp Gain Calculator
Calculate voltage gain for inverting and non-inverting op-amp configurations. Solve for gain, resistors, or output voltage.
How to Use
- Pick inverting or non-inverting topology.
- Enter Rin and Rf (feedback resistor).
- Gain = −Rf/Rin (inverting) or 1 + Rf/Rin (non-inverting).
- Optionally enter Vin to see Vout.
Show Work
Formulas
History of the Op-Amp
The operational amplifier was born in analog computing at Bell Labs in the 1940s. Loebe Julie, George Philbrick, and the MIT Rad Lab team built the first vacuum-tube op-amps to perform mathematical "operations" — addition, subtraction, integration, differentiation — for fire-control computers and later general analog computation. The name "operational amplifier" stuck because those computers solved differential equations by cascading op-amp integrators with adjustable gains.
The first monolithic (single-chip) op-amp — Bob Widlar\'s µA702 at Fairchild in 1964 — changed the game. His follow-up, the µA741 (1968), became the most produced analog IC in history: a two-input, single-output amplifier with near-ideal characteristics (high gain, high input impedance, low output impedance) for a few cents per unit. The inverting and non-inverting feedback topologies this calculator models were described by Harry Black (feedback inventor, 1927) and popularized in George Philbrick\'s 1953 Philbrick Applications Manual — the first engineering text to treat the op-amp as a reusable building block.
Modern op-amps have specialized descendants: chopper-stabilized for precision (nanovolt Vos), JFET-input for very low bias current, rail-to-rail for single-supply operation, high-speed for video and RF. But the gain equations A = 1 + Rf/Rin (non-inverting) and A = −Rf/Rin (inverting) are unchanged since Philbrick\'s manual — they follow directly from assuming infinite open-loop gain and zero input current, and they work on every op-amp you\'ll ever use.
About This Calculator
Pick inverting or non-inverting topology, enter Rin and Rf with engineering suffixes, and optionally a Vin. The tool returns voltage gain (both V/V and dB), output voltage, and a circuit-diagram visualization of the chosen topology.
Keep resistor values in the 1 kΩ–100 kΩ range as a rule of thumb — too low loads the op-amp\'s output stage, too high introduces noise and bias-current errors. For gain > 100 at signal frequencies above audio, check the op-amp\'s gain-bandwidth product: 1 MHz GBW at A = 100 gives only 10 kHz of usable bandwidth. Everything runs client-side; no values leave your browser.
About the Op-Amp Gain Calculator
Use the Op-Amp Gain Calculator — a free, easy tool for electronics and circuit design. Nothing is uploaded, and you do not need an account. Calculate voltage gain for inverting and non-inverting op-amp configurations. Solve for gain, resistors, or output voltage.
How it works
Put each value in its box and read the answer as you go. Because it recalculates live, you can play with the inputs to see how each one moves the result — handy for checking your own working or planning ahead. Everything happens on your device, so it is fast and private.
Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.
Frequently Asked Questions
Inverting vs. non-inverting?
Inverting: output is 180° out of phase with input. Gain = −Rf/Rin. Input impedance = Rin (low). Non-inverting: output in phase. Gain = 1 + Rf/Rin (always ≥ 1). Input impedance very high.
Can gain be less than 1?
Only in inverting configuration. Non-inverting always has gain ≥ 1.
What about bandwidth?
Op-amp bandwidth = Gain-Bandwidth Product (GBW) / closed-loop gain. 1 MHz GBW at gain = 100 gives 10 kHz bandwidth.
What resistors?
Keep Rin and Rf in 1kΩ – 100kΩ. Too low loads the source; too high adds noise.
How do I use the Op-Amp Gain Calculator?
Simply type your numbers and read the result, which refreshes the instant you change something. There is nothing to submit and nothing to wait for.
Do I need to install or sign up for anything?
Not at all — it runs in the browser with nothing to install and no account. After it loads once, it even works without an internet connection.
Is my information private?
Yes. Everything happens in your browser. Nothing you type is sent to a server or saved anywhere.
Common Use Cases
Microphone Preamp
Mic signal ~10mV amplified 100× (40dB) to 1V line-level.
Sensor Amplification
Strain gauge output scaled to ADC range with gain 100-1000.
Buffer Stage
Unity-gain follower isolates high-Z source from low-Z load.
Signal Conditioning
Level-shift bipolar signal to unipolar for ADC.
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