Free Online Tool

Voltage Divider Calculator

Calculate output voltage, resistor values, current draw, and power dissipation for resistive voltage divider circuits. Perfect for ADC input scaling, sensor biasing, and reference voltage generation.

Calculator Mode

V
Ω
Ω

Results

Output Voltage:6.000 V
Current Draw:600.000 μA
Power (R1):3.600 mW
Power (R2):3.600 mW
Total Power:7.200 mW

Circuit Diagram

Vin
R1
Upper Resistor
Vout (Output)
R2
Lower Resistor
GND

Formula

Vout = Vin × (R2 / (R1 + R2))
Vin: Input voltage
Vout: Output voltage
R1: Upper resistor (between Vin and Vout)
R2: Lower resistor (between Vout and GND)
Reverse Formulas:
R2 = (Vout × R1) / (Vin - Vout)
R1 = (R2 × (Vin - Vout)) / Vout
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What is a Voltage Divider?

A voltage divider is one of the most fundamental circuits in electronics. It consists of two resistors connected in series between a voltage source and ground, creating a lower voltage at the connection point between them. The output voltage is proportional to the ratio of the resistor values.

Voltage dividers are essential for scaling down voltages to safe levels for microcontrollers, creating reference voltages, biasing transistors, and interfacing sensors with different voltage requirements.

ADC Input Scaling

Scale down higher voltages to match your microcontroller's ADC input range (typically 0-3.3V or 0-5V).

Sensor Biasing

Create reference voltages for sensors and analog circuits that require specific bias points.

Battery Monitoring

Monitor battery voltage levels by scaling them down to safe measurement ranges for your circuit.

Important Design Considerations

Loading Effect: Voltage dividers work best when the load impedance is much higher than R2 (at least 10x). Low impedance loads will draw current and reduce the output voltage.

Power Dissipation: Higher current means more power wasted as heat. Use higher resistor values when possible to reduce current and power consumption.

Resistor Tolerance: Standard resistors have ±5% or ±1% tolerance. Your actual output voltage may vary slightly from calculated values.

Noise Sensitivity: Higher resistance values make the circuit more susceptible to noise. Consider adding a small capacitor across R2 for filtering.

Frequently Asked Questions

Common questions about this calculator and how to use it.

A voltage divider is a circuit with two resistors in series that produces a lower output voltage proportional to the input voltage. The output voltage equals Vin x R2 / (R1 + R2).
Voltage dividers are used to scale down voltages for microcontroller ADC inputs, bias transistors, create reference voltages, and monitor battery levels.
The loading effect occurs when a low-impedance load is connected to the output, drawing extra current and reducing the output voltage. The load impedance should be at least 10x the value of R2 for accurate results.
Use higher resistance values (10k-100k ohms) to minimize current draw. The ratio R2/(R1+R2) must equal Vout/Vin. This calculator can solve for R1 or R2 in reverse mode.
Generally no. Voltage dividers are not suitable for powering components directly because they cannot supply significant current without the output voltage dropping. Use a voltage regulator or DC-DC converter instead when powering loads.

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