Voltage Divider Calculator — Vout from R1 and R2
CalculatorA voltage divider calculator finds the output voltage across R2 in a series resistor pair using Vout = Vin × R2 / (R1 + R2).
What is it
A voltage divider is the most basic circuit for deriving a fraction of an input voltage using two series resistors. The output is taken across R2 and is set purely by the resistor ratio. Connecting a load places it in parallel with R2 and lowers the real output, so the approximation holds when the load impedance is much larger than R2 (usually 10× or more).
How to use
- 1Enter the input voltage (Vin).
- 2Enter the series resistor values R1 and R2.
- 3Press calculate to see the output voltage and circuit current.
Reference
| Vin | R1 | R2 | Vout |
|---|---|---|---|
| 12V | 10kΩ | 10kΩ | 6V |
| 9V | 6kΩ | 3kΩ | 3V |
| 5V | 3.3kΩ | 1.7kΩ | 1.7V |
Sources & standards
FAQ
How do I divide 12V down to 6V?
Use equal resistors: with R1 = R2, Vout = Vin / 2 = 6V. For example R1 = R2 = 10kΩ gives a divider current of 0.6mA.
Does connecting a load change the divider output?
Yes. The load sits in parallel with R2, lowering the effective resistance and the output voltage. Keep the load impedance at least 10 times R2 to keep the error small.
Is voltage divider input sent to a server?
No. This calculator runs in your browser and does not send input to a server.