Category: Calculators
Voltage Divider Calculator
Output voltage and current from two series resistors
Enter an input voltage and two series resistor values to calculate the output voltage at their junction and the current flowing through the divider.
Output voltage8 V
Everything on this page is processed in your browser. Nothing is uploaded.
What this tool does
A voltage divider is two resistors in series across a supply, tapped at the point between them. The output voltage is the input voltage scaled by the ratio of the bottom resistor to the total resistance: Vout = Vin × R2 / (R1 + R2).
How to use it
- Enter the input voltage.
- Enter R1 (the resistor nearest the supply) and R2 (the resistor nearest ground).
- Read the output voltage and current underneath.
Privacy
This tool runs entirely in your browser. Your input is never uploaded, stored or shared — closing the tab removes it.
Frequently asked questions
- Which resistor is R1 and which is R2?
- R1 sits between the input voltage and the output tap; R2 sits between the output tap and ground. The output voltage rises as R2 grows relative to R1.
- Does this account for a load connected to the output?
- No. This calculates the unloaded (open-circuit) output voltage. Connecting a load in parallel with R2 draws additional current and pulls the output voltage down, so a loaded divider needs a much lower R2 relative to the load's own resistance to stay accurate.
- Why use a voltage divider instead of a regulator?
- A resistive divider is simple and cheap but wastes power and sags under load, so it suits low-current jobs like biasing a sensor or scaling a signal for a microcontroller's analog input, not powering a circuit directly.