Advanced Resistor Ratio Calculator

Enter Circuit Values

Analysis Mode

R1 Value

R2 Value

Resistance Unit

Input Voltage

Resistor Tolerance (%)

Target Ratio (Optional)

Target Output Voltage (Optional)

Use R1 as the upper or feedback resistor and R2 as the lower or gain resistor, based on your selected analysis mode.

Example Data Table

Scenario	R1	R2	Input Voltage	R2/R1 Ratio	Output Voltage
Sensor Divider	10 kOhms	4.7 kOhms	12 V	0.4700	3.8367 V
Reference Split	22 kOhms	10 kOhms	5 V	0.4545	1.5625 V
Op-Amp Feedback	2.2 kOhms	8.2 kOhms	3.3 V	3.7273	2.6019 V

Formula Used

Basic resistor ratio: Ratio = R2 / R1

Voltage divider output: Vout = Vin × R2 / (R1 + R2)

Non-inverting amplifier gain: Gain = 1 + R2 / R1

Inverting amplifier gain: Gain = -R2 / R1

Parallel equivalent: Rp = (R1 × R2) / (R1 + R2)

Series current: I = Vin / (R1 + R2)

These equations help compare divider performance, estimate attenuation, and check whether your selected resistor pair hits a design target.

How to Use This Calculator

Choose the analysis mode that best matches your circuit goal.
Enter R1 and R2 using the same resistance unit.
Add the input voltage to estimate divider output, current, and resistor power.
Set tolerance to preview the likely output range caused by resistor variation.
Add a target ratio or target voltage if you want a quick fit check.
Submit the form to see the result block above, then export the results as CSV or PDF.

Frequently Asked Questions

1. What does resistor ratio mean?

It expresses the size relationship between two resistor values. Designers use it to control divider outputs, amplifier gains, attenuation levels, and reference voltages.

2. Why is R2 divided by R1 here?

That convention is common for divider output fractions and feedback network analysis. You can still read the inverse value because the calculator reports both directions.

3. Can I use kOhms or MOhms?

Yes. The tool converts selected units internally, so you can work in Ohms, kOhms, or MOhms without changing the formulas.

4. What is the tolerance window output?

It estimates the lowest and highest divider output caused by resistor tolerance drift. This helps you judge whether the design stays inside your acceptable voltage range.

5. Is this useful for op-amp design?

Yes. It quickly shows non-inverting and inverting gain values based on the same resistor pair, which is helpful during early feedback network sizing.

6. Why are current and power included?

They help check whether the divider wastes too much current or pushes a resistor near its rating. That matters in battery circuits and compact analog stages.

7. Does this replace full circuit simulation?

No. It is a fast planning tool. Loading effects, source impedance, noise, temperature, and downstream stages still need deeper analysis or simulation.