Non-Inverting Op-Amp Gain Calculator

Gain and output of a non-inverting amplifier, or resistors for a target gain.

What it does

A non-inverting amplifier has gain 1 + Rf / Rg and a very high input impedance. It can also pick resistors for a target gain.

Where it's used

Buffering and amplifying sensor signals, and voltage followers (gain = 1).

How to use it

Choose whether to calculate the gain or the resistors.
Enter Rg and either Rf or the target gain.
Enter the input voltage and supply rails.

The formula explained

G: 1 + Rf / Rg
Rf: feedback resistor (output to − input)
Rg: resistor from − input to ground

Worked example

Choosing Rf for a gain of 11.

Inputs:

Calculate: Rf for a target gain
Ground resistor Rg: 10k Ω
Target gain: 11 V/V
Input voltage: 0.3 V
Supply rails (±): 12 V

The calculator gives:

Voltage gain: 11 V/V
Gain (dB): 20.83 dB
Output voltage: 3.3 V

Tips and common mistakes

The minimum gain is 1 (a voltage follower).
The very high input impedance makes it ideal for weak sensors.
Choose the nearest E-series value and re-check the gain.

Questions people ask

How do I choose resistors for a gain I need?

Pick Rg, then Rf = Rg × (gain − 1). For a gain of 11 with Rg = 10 kΩ, Rf = 100 kΩ. Values between about 1 kΩ and 100 kΩ keep noise and loading low.

Why doesn’t the output reach the supply voltage?

Most op-amps can only swing to within about 1–2 V of each rail. If your output must get close to 0 V or the supply — common on a single 3.3 V or 5 V rail — choose a rail-to-rail output op-amp.

How do I convert the gain to decibels?

Gain in dB = 20 × log10(gain). A gain of 11 is 20.8 dB, a gain of 10 is exactly 20 dB, and a gain of 100 is 40 dB.

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