Enter the input voltage and two resistor values to calculate the output voltage.

How to Use the Voltage Divider Calculator

Input voltage and two resistor values, the classic voltage-divider circuit, solve directly for the output voltage across the second resistor.

Vout = Vin × R2 ÷ (R1 + R2)

Two resistors in series split an input voltage in proportion to their values — this is one of the first circuits anyone building electronics actually breadboards, usually to step a sensor's reference voltage down to something a microcontroller can read safely. This Voltage Divider Calculator takes the input voltage and both resistor values and returns the voltage across R2.

Worth remembering this only holds cleanly when nothing downstream is pulling meaningful current from the output — attach a low-impedance load across R2 and it starts loading down the divider, pulling the real output lower than this formula predicts.