Op-Amp Gain Calculator
Gain and output voltage of an inverting or non-inverting op-amp stage. With the formula, a worked example and typical values.
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Estimate only. Not engineering or safety advice. Check the result against the applicable standard and the equipment data, and have a competent engineer review it before it is relied on. Terms of use.
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About this calculator
This page calculates voltage gain and output voltage from feedback resistor, input resistor, input voltage and configuration. Change any value or its unit and the result updates. The steps below show the working for the default values, so you can check each line against your own method.
Limits of this calculator
Real op-amps saturate near the supply rails and have a finite gain-bandwidth product.
Cross-check: 12 reference cases, calculated from textbook formulas coded separately from the engine by the same author, agree with this calculator. This is not an independent review.
Verification status: Engineering reference
Engineering reference. Formula and method documented and tested against separately coded reference calculations. Not yet Verified: the evidence listed on this page is still needed.
What this calculator checks
- The arithmetic of the published formula for the values you entered, in the units shown.
What remains unverified
- That the inputs suit your application. Take ratings, resistances and constants from the manufacturer data sheet or project specification.
Verification register entry
| Calculation author | Rahul Sharma (author) |
|---|---|
| Technical review | No independent technical review has been carried out |
| Individual professional approval | Not recorded |
| Formula reference | not recorded |
| Standard and edition | Not applicable: Ideal inverting and non-inverting gain are textbook circuit equations. Device bandwidth, offset, stability and output limits are manufacturer-specific. |
| Standard review state | Not applicable |
| Scope-screening note | not recorded |
| Cross-check test cases | 12 reference vectors (tests/reference_vectors.json) |
| Review date | not recorded |
| Next review date | not recorded |
| Status | Engineering reference |
Needed before this calculator can be marked Verified: reviewer name, qualification and review date; exact formula reference; formula source (textbook or standard); next review date.
Formula
Worked example
| Input | Value |
|---|---|
| Feedback resistor | 100 kΩ |
| Input resistor | 10 kΩ |
| Input voltage | 0.5 V |
| Configuration | Inverting |
- A = −Rf / Rin = -10
- Vout = -10 × 0.5 = -5 V
Assumptions
- Ideal op-amp
- Output stays within the supply rails
Real op-amps saturate near the supply rails and have a finite gain-bandwidth product.
Inputs and results
| Input | Unit | Allowed or shown | Note |
|---|---|---|---|
| Feedback resistor | kΩ | greater than 0 kΩ | |
| Input resistor | kΩ | greater than 0 kΩ | |
| Input voltage | V | greater than 0 V | |
| Configuration | (choice) | Inverting; Non-inverting |
| Result | Unit | Allowed or shown | Note |
|---|---|---|---|
| Voltage gain | (number) | Shown to 3 decimal places | |
| Output voltage | V | Shown to 3 decimal places |
How it is calculated
Each input is converted to the base unit of its quantity, the formula above is applied in the order shown in the worked example, and each result is shown in the unit you choose. Results are held at full precision and rounded only for display, except where a step selects a standard size, as the worked example shows. A value outside its allowed range is refused with a message instead of giving a result.
How the result changes with feedback resistor
| Feedback resistor (kΩ) | Voltage gain | Output voltage (V) |
|---|---|---|
| 10 | -1 | -0.5 |
| 25 | -2.5 | -1.25 |
| 50 | -5 | -2.5 |
| 100 | -10 | -5 |
| 200 | -20 | -10 |
| 400 | -40 | -20 |
| 1,000 | -100 | -50 |
Other inputs are the same as in the worked example above.
Standards and further reading
These are textbook circuit relationships. The component data sheet sets the real limits, tolerances and ratings, and takes priority over the calculated value.
Frequently asked questions
What do I need to enter?
Enter feedback resistor, input resistor, input voltage and configuration. Change the unit of a value with its selector and the result stays the same.
What does this calculator assume?
Ideal op-amp. Output stays within the supply rails.
Which calculators should I use next?
Common next steps are Voltage Divider and Decibel Converter. The related links at the bottom of this page open them.
How accurate are the results?
Every figure comes from the same tested engine as the Elecmetric calculators and is meant for estimating. 12 reference cases, calculated from textbook formulas coded separately from the engine by the same author, agree with this calculator. This is not an independent review. Check design values against the standard and the equipment data you work to.
Formula guides and reference
Longer explanations with worked examples and tables, written for the same topic.
- Op-Amp Formulas: Inverting and Non-Inverting: Op-amp gain formulas for the inverting and non-inverting amplifier, voltage follower and the summing amplifier
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