Voltage Divider Calculator
Calculate output voltage from input voltage and two resistors.
Voltage Divider Formula
Vout = Vin × R2/(R1 + R2).
How a Voltage Divider Works
A voltage divider uses two series resistors to produce a fraction of the input voltage. The output is taken across R2, so the resistor ratio determines the voltage fraction.
Example Calculation
With Vin = 12 V, R1 = 1 kΩ and R2 = 2 kΩ, Vout = 12 × 2/(1+2) = 8 V.
Factors and Interpretation
The simple formula assumes the output is unloaded. Connecting a load in parallel with R2 changes the effective resistance and therefore the output voltage. Resistor tolerances also affect accuracy.
Frequently Asked Questions
Can Vout be greater than Vin?
No. A passive two-resistor divider produces an output between 0 and Vin for positive resistor values.
What happens if R1 equals R2?
Vout is half of Vin.
Does a connected load affect the result?
Yes. The load changes the lower-leg resistance unless its impedance is very high.
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Formula and Practical Limits
An unloaded two-resistor voltage divider gives Vout = Vin·R2/(R1+R2). A connected load changes the effective lower resistance and can reduce output voltage, so high-impedance loading assumptions matter in practical circuits.