Op-Amp Gain Calculator
Gain of inverting and non-inverting op-amp stages from the feedback resistors, output for an input with clipping at your rails, and the R_f for a target gain.
What an op-amp stage will do to a signal — gain in ratio and dB, the output voltage, and whether it runs into the rails — plus the resistor to fit for the gain you want.
Example: R_f = 100 kΩ, R_in = 10 kΩ: inverting gain −10 (20 dB), non-inverting 11. With ±12 V rails and 1.5 V headroom, 0.5 V in gives −5 V out; anything above 1.05 V in clips.
The gain is set by two resistors.
The rails set the limit.
The two classic stages, where clipping comes from, and what an ideal op-amp leaves out.
Inverting and non-inverting
With negative feedback an ideal op-amp holds its two inputs at the same voltage and draws no input current. In the inverting stage the input resistor and feedback resistor share the same current, so the gain is −R_f ÷ R_in and the stage presents R_in to the source. In the non-inverting stage the feedback pair is a divider from the output to the inverting pin, so the gain is 1 + R_f ÷ R_g and the input sees the op-amp's own high impedance. Gain in dB is 20 log₁₀ of the magnitude; the sign is a phase inversion, not a loss.
Rails, headroom and clipping
The output cannot exceed the supplies, and most op-amps stop a volt or two short of each rail — the headroom figure on the datasheet, which you enter. The page multiplies input by gain, clips to those limits and flags it, and reports the largest input that stays clean. On a single supply the output cannot go below ground, so an inverting stage or a signal swinging both ways needs a mid-supply bias; the page reminds you.
What the datasheet still owns
Real op-amps have finite open-loop gain, an input offset, bias currents that develop voltages across large resistors, a gain-bandwidth product that limits bandwidth to GBW ÷ gain, a slew-rate limit and a maximum output current. None of those are modelled here; the page flags very high gains and leaves the rest to the part you choose. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.
SOURCES
- Ideal op-amp inverting and non-inverting amplifier relations — standard electronics (e.g. Horowitz & Hill, The Art of Electronics, chapter 4)
Last reviewed 19 September 2026. How results are checked: How we verify.