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Voltage Divider Calculator — Solve Vout From Two Resistors
Enter input voltage and two resistor values to calculate the output voltage of a simple voltage divider circuit, using Vout = Vin × R2/(R1+R2) — one of the most common building blocks in basic circuit design, for level-shifting a signal or creating a reference voltage.
How to use Voltage Divider
- Enter input voltage and both resistor values.
- Read the calculated output voltage.
- Adjust resistor values to hit a target Vout.
Frequently asked questions
- What is the voltage divider formula?
- Vout = Vin × R2 / (R1 + R2), where R2 is the resistor across which you are measuring Vout — swapping which resistor is R1 vs R2 changes which node you are calculating.
- Why does a voltage divider load down under current draw?
- The formula assumes no current is drawn from the Vout node; connecting a real load in parallel with R2 changes the effective resistance and pulls Vout lower than the ideal calculation — this matters when driving anything but a very high-impedance input.
- What is a common real-world use for this circuit?
- Scaling down a sensor or battery voltage to a safe range for a microcontroller's analog input pin is one of the most frequent uses in hobbyist electronics.
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