Voltage Divider Calculator

Voltage Divider Circuits

A voltage divider uses two resistors in series to produce an output voltage lower than the input. The output is taken across the lower resistor. This simple circuit appears in sensor biasing, reference voltages, and level shifting.

Formula

$$V_{out} = V_{in} \times \frac{R_2}{R_1 + R_2}$$

$V_{in}$ is the supply voltage, $R_1$ is the upper resistor connected to the input, and $R_2$ is the lower resistor connected to ground with the output taken at the junction.

Design Considerations

The divider ratio depends only on resistor values, not on the absolute magnitudes. However, loading from a connected circuit draws current and changes the output. For accurate results, make the divider current much larger than the load current, or use a buffer amplifier.

Related tools: LM317 Calculator and Op-Amp Gain Calculator.

Frequently Asked Questions

Does the divider work with AC signals?

Yes, for AC the same ratio applies if reactances replace resistances. For frequency-dependent circuits, use impedance values instead of pure resistance.

What happens if R1 or R2 is zero?

If R2 is zero, Vout is 0 V. If R1 is zero, Vout equals Vin (assuming no load). The calculator requires both resistors to be positive for a valid result.

How do I choose resistor values?

Pick a ratio that gives the desired Vout, then scale both resistors so the divider current is appropriate for your load and power budget.

Does load current affect the output?

Yes. A connected load forms a parallel resistance with R2 and lowers Vout. Use high-value resistors or a buffer when the load draws significant current.

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Voltage Divider Calculator

Voltage Divider Circuits

Formula

Design Considerations

Frequently Asked Questions

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