Voltage Divider Calculator
Calculate output voltage, current draw, and power dissipation for a two-resistor voltage divider � ideal for ADC input scaling, sensor biasing, and reference voltages.
Results
What is it?
A voltage divider uses two resistors in series to scale down a voltage: Vout = Vin � R2 / (R1 + R2). It is one of the most fundamental circuits in electronics, used for ADC input scaling (e.g., reading 12V with a 3.3V MCU), sensor biasing, and generating reference voltages.
How to use
Enter the input voltage and the two resistor values. Vout, current draw, and power dissipation in each resistor are calculated. To design for a target Vout, choose R2/R1 ratio = Vout/(Vin - Vout). Use the E24 or E96 resistor series for precision applications.
Example scenario
Scale 12V to 3.3V for an Arduino analog input: R2/(R1+R2) = 3.3/12 = 0.275. Choose R2 = 10kO, R1 = 27kO ? Vout = 12�10/(10+27) = 3.24V ?. Current = 12/37000 = 0.324 mA (low quiescent draw).
Pro tip
A voltage divider is only accurate when the load impedance is much larger than R2 (at least 10�). If the load draws significant current, it will pull Vout down. Use a unity-gain op-amp buffer after the divider for low-impedance loads. For battery monitoring, use high-value resistors (100kO+) to minimize quiescent current drain.