Calculate the closed-loop gain of an operational amplifier in inverting, non-inverting, differential (difference) or voltage-follower configuration. See the gain in V/V and dB, the output voltage, whether it clips at the supply rails, and the closed-loop bandwidth.
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Configuration
Inverting: input resistor · Non-inverting: resistor to ground (R_g)
V
V
V
V
For ±12 V enter 12; leave empty to ignore clipping
V
0 for rail-to-rail op-amps
MHz
e.g. 1 MHz for a 741 or TL07x-class part (check datasheet)
Enter your values to see the result.
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How to use the Op Amp Gain Calculator
Choose the configuration: inverting, non-inverting, differential or voltage follower.
Enter the resistor values and their unit.
Enter the input voltage (or V₁ and V₂ for a differential amplifier).
Optionally add the supply and GBW to check clipping and bandwidth.
Read the gain and output, then check the transfer curve for saturation.
Op amp gain formulas
Configuration
Gain
Input impedance
Noise gain
Inverting
G = −R_f ÷ R_in
R_in
1 + R_f/R_in
Non-inverting
G = 1 + R_f ÷ R_g
Very high
1 + R_f/R_g
Voltage follower
G = 1
Very high
1
Difference (R4/R3 = R2/R1)
V_out = (R2/R1)(V₂ − V₁)
R1 (V₁), R3 + R4 (V₂)
1 + R2/R1
These are ideal-op-amp results: infinite open-loop gain, no input current and no offset. They are accurate as long as the open-loop gain at the signal frequency is much larger than the noise gain.
Gain, ratio and decibels
|G| (V/V)
dB
Inverting R_f / R_in
Non-inverting R_f / R_g
1
0
10 kΩ / 10 kΩ
Follower (no resistors)
2
6.02
20 kΩ / 10 kΩ
10 kΩ / 10 kΩ
5
13.98
51 kΩ / 10 kΩ (≈5.1)
39 kΩ / 10 kΩ (≈4.9)
10
20
100 kΩ / 10 kΩ
9.1 kΩ / 1 kΩ (≈10.1)
100
40
1 MΩ / 10 kΩ
100 kΩ / 1.01 kΩ (E96)
Keep resistor values roughly between 1 kΩ and 1 MΩ: much lower values load the output, much higher values add noise and offset from input bias currents.
Frequently asked questions
What is the gain of an inverting op amp?
G = −R_f ÷ R_in. With R_f = 100 kΩ and R_in = 10 kΩ the gain is −10: a 0.3 V input gives −3 V out. The minus sign means the output is inverted (180° out of phase).
What is the gain of a non-inverting op amp?
G = 1 + R_f ÷ R_g, where R_g goes from the inverting input to ground. With R_f = 10 kΩ and R_g = 1 kΩ the gain is 11. The gain can never be less than 1 in this configuration.
How do I convert op amp gain to decibels?
Voltage gain in dB = 20 × log₁₀(|G|). A gain of 10 is 20 dB, 100 is 40 dB and 2 is about 6.02 dB. The sign (inversion) does not affect the dB value.
How does a differential (difference) amplifier work?
With four resistors where R4/R3 = R2/R1, the output is V_out = (R2/R1) × (V₂ − V₁), so it amplifies the difference and rejects voltage common to both inputs. If the ratios do not match, part of the common-mode voltage leaks to the output.
Why is my output voltage lower than the gain predicts?
An op amp cannot drive its output beyond its supply rails. Most classic op amps stop 1–2 V short of each rail; rail-to-rail types get within tens of millivolts. Enter the supply voltage and headroom to see where the output clips.
What limits the bandwidth of an op amp circuit?
For voltage-feedback op amps the closed-loop bandwidth is roughly the gain-bandwidth product divided by the noise gain (1 + R_f/R_in). A 1 MHz GBW op amp set to a gain of 10 (noise gain 11 for inverting) has about 91 kHz of bandwidth.
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