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Voltage Divider Calculator
Find the output voltage of a two-resistor divider.
Output voltage
—
Across R2.
| Current | — |
|---|---|
| Input | — |
| R1 | — |
| R2 | — |
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Enter your figures above to see the step-by-step working.
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How the Voltage Divider Calculator Works
A voltage divider is two resistors in series that split an input voltage into a smaller output taken across the second resistor. The output is Vin × R2 ÷ (R1 + R2). With 12 V, a 1kΩ R1 and a 2kΩ R2, the output is 8 volts — two-thirds of the input, matching R2’s two-thirds share of the resistance.
Dividers are everywhere in electronics for setting reference voltages and scaling signals. Keep in mind the output sags if you draw much current from it.
Vout = Vin × R2 ÷ (R1 + R2)
Frequently Asked Questions
What is a voltage divider?
Two series resistors that produce a fraction of the input voltage at their junction, set by the resistor ratio.
How do you calculate the output?
Vout = Vin × R2 ÷ (R1 + R2). The output equals the input times R2’s share of the total resistance.
Why does the output drop under load?
Drawing current adds a parallel path across R2, lowering the effective resistance and the output voltage.
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