An operational amplifier (op-amp) is a versatile analog building block. Inverting and non-inverting configurations use just two resistors to set precise voltage gain. This calculator computes gain, output formula, and bandwidth estimate from R1 and R2 values.
Resistor Values
Enter R1, R2 and click Calculate
How to Use the Op-Amp Gain Calculator
This operational amplifier calculator computes voltage gain for the two most common op-amp configurations. Select inverting or non-inverting mode, enter R1 and R2, and optionally enter the gain-bandwidth product for bandwidth estimation.
Inverting vs Non-Inverting
In the inverting configuration, the input signal connects through R1 to the inverting (−) terminal. R2 connects from the output to the inverting terminal (feedback). Gain = −R2/R1 (negative = inverted). In the non-inverting configuration, the signal connects directly to the non-inverting (+) terminal. R1 connects to ground and R2 connects from output to the inverting terminal. Gain = 1 + R2/R1 (positive = in-phase).
Resistor Value Guidelines
Use 1kΩ to 100kΩ for audio and general signal processing. Values below 1kΩ load the signal source and waste current. Values above 100kΩ become sensitive to op-amp input bias currents (causes DC offset errors). For precision designs, use 0.1% tolerance resistors. For matched gain, use resistors from the same batch or a matched pair IC.
Frequently Asked Questions
Is this op-amp calculator free?
Yes, completely free. Calculate gain for any op-amp configuration without any account or payment.
Is my data private?
All calculations run in your browser. No data is sent to any server.
What is the gain formula for an inverting op-amp?
For an inverting amplifier: Gain = -(R2/R1). The negative sign means the output is inverted (180° phase shift). For example, R1=1kΩ and R2=10kΩ gives a gain of -10, meaning a 1V input produces a -10V output.
What is the gain formula for a non-inverting op-amp?
For a non-inverting amplifier: Gain = 1 + (R2/R1). The output is in phase with the input. With R1=1kΩ and R2=9kΩ, gain = 10. A 1V input produces a +10V output.
What is gain-bandwidth product?
The gain-bandwidth product (GBW) is a constant for a given op-amp that represents the tradeoff between gain and frequency. If GBW = 1MHz and gain = 10, the -3dB bandwidth is 100kHz. Higher gains reduce bandwidth. Check your op-amp's datasheet for its GBW specification.
How do I choose R1 and R2 values?
Use impedances between 1kΩ and 100kΩ for general audio and signal processing. Values below 1kΩ waste power and can load signal sources. Values above 100kΩ become sensitive to op-amp input bias currents. For precision applications, match resistor tolerances (use 1% or 0.1% resistors).
What is the virtual ground concept?
In an ideal op-amp with negative feedback, the inverting input is held at the same potential as the non-inverting input (virtual ground). For inverting configs with non-inverting tied to GND, the inverting input is at 0V (virtual ground), which determines how current flows through R1 and R2.