Engineering Calc Tools

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Op-Amp Gain Calculator (Inverting and Non-Inverting)

Gain and output voltage of ideal inverting, non-inverting, summing and difference op-amp amplifiers, with rail saturation.

Tool no.
ECT-K08
Rev
1.0
Updated
Oct 2026
Method
Ideal op-amp rules
How to use this calculator

Pick the configuration and enter the resistors and input voltages. Add the supply rails to see whether the output clips, and a load resistor for the output current.

Formulas

InvertingG = −Rf/Rin
Non-invertingG = 1 + Rf/Rg
SummingVout = −Rf(V1/R1 + V2/R2 + …)
DifferenceVout = (Rf/R1)(V2 − V1)

Worked example

Inverting amplifier, Rf = 100 kΩ, Rin = 10 kΩ, Vin = 0.5 V (the default)

  1. G = −100/10 = −10.
  2. Vout = −10 × 0.5 = −5 V.
  3. With the same resistors as a non-inverting amplifier, G = 1 + 10 = 11 and Vout = 5.5 V.

Frequently asked questions

What are the ideal op-amp rules?

No current into either input, and with negative feedback the two inputs are at the same voltage. Every formula here follows from those two.

When does the output saturate?

When G·Vin asks for more than the supply can give. A 741 on ±15 V swings only to about ±13 V; rail-to-rail parts get close to the rails.