Op-Amp Gain Calculator
Enter the input resistor Rin and feedback resistor Rf, then choose the topology to find the closed-loop voltage gain and the gain in decibels. An inverting amplifier gives a negative gain of minus Rf over Rin, while a non-inverting amplifier gives 1 plus Rf over Rin.
How to use the op-amp gain calculator
- Enter the input resistor Rin in ohms (or kilohms).
- Enter the feedback resistor Rf in ohms (or kilohms).
- Choose inverting or non-inverting.
- Read the voltage gain and the gain in decibels.
Examples
Inverting, Rin 1k and Rf 10k
Rin = 1000 ohm, Rf = 10000 ohm, inverting
gain = -10, 20.00 dB
Non-inverting, same resistors
Rin = 1000 ohm, Rf = 10000 ohm, non-inverting
gain = 11, 20.83 dB
Frequently asked questions
What is the inverting amplifier gain formula?
Gain equals minus the feedback resistor over the input resistor, gain = -Rf / Rin. With Rin = 1k and Rf = 10k the gain is -10.
What is the non-inverting amplifier gain formula?
Gain equals 1 plus the feedback resistor over the input resistor, gain = 1 + Rf / Rin. The output is always at least unity gain.
Why is the inverting gain negative?
The output is 180 degrees out of phase with the input, so the gain carries a minus sign. The magnitude is still Rf over Rin.
How is gain converted to decibels?
Gain in decibels is 20 times the base-10 logarithm of the gain magnitude. A gain of 10 is 20 dB and a gain of 11 is about 20.83 dB.
Does this assume an ideal op-amp?
Yes. It uses the ideal closed-loop formulas and ignores finite open-loop gain, bandwidth and input offsets, which is accurate for most low-frequency designs.
Related tools
Voltage Divider Calculator
Calculate the output of a resistive voltage divider. Enter the input voltage and two resistors to get Vout, the current and the divider ratio instantly.
Ohm's Law Calculator
Solve Ohm's law online. Enter any two of voltage, current, resistance or power and get the other two, with the V, I, R and P formulas shown.
RC Time Constant Calculator
Find the RC time constant from resistance and capacitance, plus charge times and the cutoff frequency. Enter any two of R, C and tau to solve the third.
555 Timer Calculator
Calculate 555 timer astable frequency, period, high and low times and duty cycle from R1, R2 and the timing capacitor. Free oscillator design helper.
Battery Life Calculator
Estimate how long a device runs on a battery from its capacity in mAh and current draw in mA. Includes a real-world efficiency factor for an honest figure.
Bernoulli Equation Calculator
Solve Bernoulli's equation for the downstream pressure from density, upstream pressure, two velocities and two elevations for steady incompressible flow.