About the Op Amp Gain Calculator
An operational amplifier with two resistors makes an amplifier whose gain is set by the resistor ratio. Pick the circuit, enter Rin and Rf, the input voltage, the supply voltage and the gain-bandwidth product of your chip. The calculator returns the voltage gain as a ratio and in decibels, the output voltage, a warning when the output would clip against the supply rails, the -3 dB bandwidth and the input impedance. It covers the inverting amplifier, the non-inverting amplifier, the voltage follower and a difference amplifier with matched resistors. It assumes an ideal op amp with negative feedback, so use it for design estimates and homework.
Updated October 2026
How to use the Op Amp Gain Calculator
- 1Choose the circuit: inverting, non-inverting, follower or difference.
- 2Enter Rin and Rf in kilohms.
- 3Enter the input voltage and the supply rail voltage.
- 4Enter the gain-bandwidth product of your op amp.
- 5Read the gain, the output voltage and the bandwidth.
Why feedback sets the gain
An op amp has enormous gain on its own, but by feeding some of the output back to the inverting input you trade that gain for accuracy. With negative feedback the two inputs sit at nearly the same voltage, and the output takes whatever value is needed to make that true. The result depends on the resistor ratio, not on the chip, which is why the gain is stable.
The price is bandwidth. A chip with a 1 MHz gain-bandwidth product gives about 100 kHz at a gain of 10 and 10 kHz at a gain of 100.
Choosing a circuit
- Inverting: simple, gain below 1 possible, input impedance equals Rin.
- Non-inverting: very high input impedance, gain of at least 1.
- Follower: buffer with unity gain.
- Difference: amplifies the voltage between two inputs, with matched resistors.
- For audio, check the noise and the supply voltage of the chip.
Related tools
Set the resistors with the Resistor Calculator and read colour bands with the Resistor Color Code Calculator. The Voltage Divider Calculator helps bias the input, the Decibel Calculator converts a gain to dB and back and the Ohm's Law Calculator checks currents. Always check the datasheet limits of your op amp.
Features
- Inverting, non-inverting, follower and difference amplifiers
- Gain as a ratio and in dB
- Output voltage with supply clipping
- Bandwidth from gain-bandwidth product
- Input impedance
- Clear errors for impossible values
- Free and private
Frequently asked questions
What is the gain of an inverting amplifier?
It is minus Rf divided by Rin. With Rin 10 kilohms and Rf 100 kilohms the gain is -10, so a 0.5 V input gives -5 V.
What is the gain of a non-inverting amplifier?
It is 1 plus Rf divided by Rin. The same resistors give a gain of 11, and the output has the same sign as the input.
Why does the output stop at the supply voltage?
An op amp cannot output more than its supply rails, and many cannot get closer than 1 to 2 volts. The calculator shows when the ideal result would be clipped.
What is gain-bandwidth product?
It is the frequency where the open-loop gain falls to 1. The bandwidth of your amplifier is roughly this value divided by the closed-loop gain.
Which resistor values should I use?
Values between about 1 kilohm and 1 megohm work for most circuits. Very large values add noise and are sensitive to input bias current.
Does it model offset or noise?
No. It uses the ideal op amp model. Real chips add input offset, bias currents, noise and limited slew rate.
What is a voltage follower for?
It has a gain of 1 but a very high input impedance and low output impedance, so it buffers a signal without loading the source.