What is the gain formula for an inverting op-amp?

The voltage gain of an inverting amplifier is Av = -(Rf / Rin). The negative sign means the output is 180° out of phase with the input. For example, Rf = 100 kΩ and Rin = 10 kΩ gives a gain of -10.

What is the gain formula for a non-inverting op-amp?

The voltage gain of a non-inverting amplifier is Av = 1 + (Rf / Rin). The output is in phase with the input. Using the same resistors (Rf = 100 kΩ, Rin = 10 kΩ) gives a gain of +11.

What happens if Rin is 0 in a non-inverting circuit?

Setting Rin to 0 (or removing it entirely) turns the non-inverting amplifier into a unity-gain voltage follower with Av = 1. This is a common buffer configuration.

Does this calculator assume an ideal op-amp?

Yes. The formulas assume infinite open-loop gain, infinite input impedance, and zero output impedance — the ideal op-amp model used in most textbook calculations. Real-world deviations depend on the specific IC and operating frequency.

How do I choose resistor values for a target gain?

Pick a convenient Rin (e.g. 10 kΩ), then solve for Rf. For an inverting amplifier with gain -5: Rf = |Av| × Rin = 5 × 10 kΩ = 50 kΩ. Use the nearest standard E24 or E96 value.

Can I enter resistor values in kilohms or megaohms?

Yes. Use the unit selector next to each resistor field. The calculator converts all values to ohms before computing gain, so the unit choice does not affect the result.

Op-Amp Gain Calculator

Name: Op-Amp Gain Calculator
Availability: InStock
Author: Nham Vu

Enter resistor values to instantly calculate the voltage gain of inverting and non-inverting op-amp configurations.

Configuration

Input Resistor (R_in)

Feedback Resistor (R_f)

Input Voltage V_in (optional)

Circuit Diagram

Inverting Amplifier

Results

Enter resistor values and click Calculate Gain

Common Gain / Resistor Combinations

\|Gain\|	Rin	Rf	Inv. Av
1	10 kΩ	10 kΩ	−1
2	10 kΩ	20 kΩ	−2
5	10 kΩ	50 kΩ	−5
10	10 kΩ	100 kΩ	−10
47	10 kΩ	470 kΩ	−47

Click a row to load those values.

Summary

Enter resistor values to instantly calculate the voltage gain of inverting and non-inverting op-amp configurations.

How it works

Select the op-amp configuration: inverting or non-inverting.
Enter the input resistor (Rin) value in ohms, kilohms, or megaohms.
Enter the feedback resistor (Rf) value in the same or different unit.
The calculator applies the standard gain formula and displays the result.
Optionally enter an input voltage to see the expected output voltage.

Use cases

Designing audio amplifier stages with precise gain requirements.
Verifying resistor selections in analog signal conditioning circuits.
Teaching or learning op-amp theory with instant feedback.
Quickly checking gain when prototyping with LM741, TL071, or similar ICs.
Converting a desired gain value back to resistor ratios.
Comparing inverting vs. non-inverting behavior for a given gain magnitude.
Troubleshooting op-amp circuits by recalculating expected gain.
Scaling sensor output signals to match ADC input ranges.

Frequently Asked Questions

Related tools

Amps To Ohms Resistor Color Code Calculator Capacitor Code Calculator

Last updated: 2026-05-23 · Reviewed by Nham Vu