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Op-Amp Gain Calculator

Compute the voltage gain (V/V and dB) of inverting and non-inverting op-amp amplifiers from the resistor values.

Voltage gain
11 V/V
Av = 1 + Rf/Rin
Gain in dB
20.83 dB
20·log₁₀|Av|

Inverting gain is negative (180° phase shift); non-inverting is always ≥ 1. Only the resistor ratio sets the gain.

Disclaimer: This calculator is provided for general informational and educational purposes only, on an “as is” basis and without any warranty of accuracy or fitness for a particular purpose. Results may contain errors — always verify independently before relying on them in real designs. PartAndStock accepts no liability for any loss or damage arising from use of this tool, including when embedded on third-party sites.

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Step-by-step: How to Calculate Op-Amp Gain

How to use

  1. 1Pick the topology: inverting or non-inverting.
  2. 2Enter the input/ground resistor (Rin or Rg) and the feedback resistor (Rf) in kΩ.
  3. 3The voltage gain (V/V) and its dB value are computed instantly.

How it works

Enter the input and feedback resistors to find the voltage gain of an inverting or non-inverting op-amp circuit, as both a ratio and in dB.

Non-inverting: Av = 1 + Rf/Rin · Inverting: Av = −Rf/Rin · Gain(dB) = 20·log₁₀|Av|

How the resistor ratio sets the gain

An ideal op-amp with feedback holds its two inputs equal (virtual short) and draws no input current. Those two rules tie the gain to just two resistors. In the non-inverting layout the signal enters the (+) input and the gain is Av = 1 + Rf/Rin (always ≥ 1). In the inverting layout the signal enters the (−) input through Rin, the output is inverted, and Av = −Rf/Rin.

dB, bandwidth and limits

Gain is often expressed in decibels: dB = 20·log₁₀|Av|. A real op-amp's gain isn't infinite and its gain-bandwidth product (GBW) is constant: raising the gain lowers the amplifier's bandwidth. The output also can't exceed the supply rails — high gain plus a large input clips the output.

Worked examples

  • Non-inverting: Rin=1 kΩ, Rf=10 kΩ → Av = 1 + 10/1 = 11 V/V (~20.8 dB)
  • Inverting: Rin=1 kΩ, Rf=10 kΩ → Av = −10 V/V (~20 dB)
  • Non-inverting: Rin=1 kΩ, Rf=0 → Av = 1 (buffer/follower)

Gain ↔ dB

Gain (V/V)dB
10 dB
26 dB
1020 dB
10040 dB
100060 dB

Frequently Asked Questions

What is the non-inverting op-amp gain formula?+
Av = 1 + Rf/Rin. E.g. Rf=10 kΩ, Rin=1 kΩ → 11 V/V. In this layout the gain is always 1 or more and the output is in phase with the input.
What's the difference between inverting and non-inverting?+
Inverting output is phase-reversed (Av = −Rf/Rin) with input impedance equal to Rin; non-inverting output is in phase (Av = 1+Rf/Rin) with very high input impedance.
Can I get a gain below 1?+
Yes, but only in the inverting layout: choose Rf < Rin and |Av| < 1 (attenuation). The non-inverting layout can never go below 1.
How do I convert gain to dB?+
For voltage gain, dB = 20·log₁₀|Av|. E.g. a 10× gain is 20 dB, a 100× gain is 40 dB.
Can I raise the gain as much as I want?+
No. Because the gain-bandwidth product (GBW) is constant, high gain lowers bandwidth; the output also can't exceed the supply. For very high gain, cascade stages.

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