Voltage Divider Calculator
Calculate the output voltage, resistor values, or input voltage for voltage divider circuits
A voltage divider is a circuit that uses two resistors in series to create an output voltage (Vout) that's a fraction of the input voltage (Vin).
Input Parameters
Results
Enter values and click Calculate to see results
Calculating...
Power Analysis
Tolerance Analysis
Recommended E24 Resistors
What is a Voltage Divider?
A voltage divider is a passive circuit that uses two resistors in series to create an output voltage that's a fraction of the input voltage. It's one of the most fundamental circuits in electronics.
This principle is widely used in electronic design for tasks like scaling sensor outputs, creating reference voltages, and level-shifting between components.
Practical Considerations
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Loading Effects
Any load connected to Vout forms a parallel circuit with R2, reducing the effective resistance and output voltage.
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Power Dissipation
Resistors dissipate power as heat: P = V²/R or P = I²R. Choose appropriate wattage ratings.
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Resistor Tolerance
Component tolerances affect output precision. Higher precision resistors provide more predictable results.
Common Applications
Reference Voltages
Creating stable reference voltages for microcontrollers and op-amps.
Sensor Interfaces
Scaling sensor outputs to match ADC input ranges.
Level Shifting
Converting between different voltage levels (e.g., 5V to 3.3V).
Battery Monitoring
Scaling battery voltage for microcontroller monitoring.
Design Tips
- Choose higher resistor values (kΩ or MΩ range) to minimize power consumption
- Use 1% or better tolerance resistors for precision applications
- Consider temperature coefficient for varying environments
- Add a small capacitor across R2 for filtering high-frequency noise
- Use a buffer amplifier after the divider when driving loads
Frequently Asked Questions
What is the formula for a voltage divider?
The voltage divider formula is: Vout = Vin × (R2 / (R1 + R2)) where Vin is the input voltage, R1 is the top resistor, and R2 is the bottom resistor. This formula calculates the output voltage at the junction between the two resistors.
How do I calculate resistor values for a specific output voltage?
To calculate resistor values for a specific output voltage (Vout) from a known input voltage (Vin), use our calculator in "Calculate R1" or "Calculate R2" mode. You'll need to determine one resistor value first, then calculate the other based on your desired voltage ratio.
Why use a voltage divider instead of a voltage regulator?
Voltage dividers are simpler, cheaper, and require fewer components than voltage regulators. They're ideal for creating reference voltages or scaling sensor outputs. However, they cannot maintain a constant output under varying load conditions, unlike voltage regulators.