Voltage Divider Calculator
Calculate output voltage or required resistor values for a voltage divider circuit.
Calculate Output Voltage
Find Required Resistors
Calculated Result
Interactive Circuit
Understanding Voltage Dividers
A voltage divider is a circuit that turns a higher voltage into a lower one using two resistors in series:
Vout = Vin × (R2 / (R1 + R2))
Where:
- Vout = Output voltage
- Vin = Input voltage
- R1 = Upper resistor
- R2 = Lower resistor
R1 = R2 × ((Vin / Vout) - 1)
For finding R1 when:
- You know desired Vout
- You choose a value for R2
- Typically R2 = 10kΩ
- Then solve for R1
Voltage Divider Design Guide
Common Applications
Sensor Interfacing
Converting 5V sensor outputs to 3.3V for microcontrollers: 5V → 3.3V needs R1 = 5.1kΩ, R2 = 10kΩ
Reference Voltages
Creating reference voltages for ADCs: 12V → 2.5V needs R1 = 38kΩ, R2 = 10kΩ
Design Considerations
Power Dissipation
Choose resistors with adequate power ratings. P = V²/R for each resistor.
Load Effects
Consider the load impedance. It should be much higher than R2 (>10x) to maintain accuracy.
Tips for Success
Use Standard Values
Choose resistors from the E12 or E24 series for better availability.
Tolerance
Use 1% tolerance resistors for better accuracy in critical applications.
Current Draw
Higher resistance values reduce power consumption but may increase noise.
Common Issues
Output Voltage Too Low
- • Check for correct resistor values
- • Verify input voltage
- • Check for excessive load current
- • Look for poor connections
Unstable Output
- • Add bypass capacitors
- • Check for noise sources
- • Verify power supply stability
- • Consider shielding if needed