What is a Voltage Divider?

A voltage divider is one of the simplest and most commonly used passive circuits in electronics. It uses two resistors in series to produce an output voltage that is a fraction of the input voltage. The output is taken from the junction between the two resistors.

The Voltage Divider Formula

Vout = Vin × (R2 / (R1 + R2))

Where R1 is the top resistor (between Vin and Vout), and R2 is the bottom resistor (between Vout and ground).

How to Use This Calculator

Enter the input voltage (Vin) and the two resistor values (R1 and R2). The calculator computes Vout, the current through the divider, and the power dissipated.

Practical Examples

Example 1: Vin = 12V, R1 = 10kΩ, R2 = 5kΩ. Vout = 12 × (5000 / 15000) = 4V.

Example 2: Stepping 5V down to 3.3V for a microcontroller input. R2/(R1+R2) = 0.66, so R1 = 10kΩ, R2 ≈ 20kΩ gives 5 × (20/30) = 3.33V.

Key Applications

• Sensor signal conditioning: Scaling voltages to ADC input ranges.
• Biasing transistors: Setting the base voltage of BJT amplifier stages.
• Resistive sensor reading: Thermistors, LDRs, and potentiometers in divider configurations.
• Reference voltages: Generating sub-rail reference voltages in analog circuits.

Limitations

A voltage divider is only accurate when the load impedance is much higher than R2 (typically 10× or more). Heavy loading shifts Vout below the calculated value. For driving loads, use a voltage regulator or op-amp buffer instead.