Voltage Divider Calculator
Compute output voltage of a voltage divider (Vout = Vin × R2/(R1+R2)).
Enter Values
Fill in the fields and press Calculate to see instant results.
What is the Voltage Divider Calculator?
The Voltage Divider Calculator computes the output voltage of a voltage divider circuit, which is a fundamental circuit design technique that reduces a higher voltage to a lower desired voltage using series resistors. Voltage dividers are widely used in sensor interfaces, signal conditioning, reference voltage generation, and impedance matching. This calculator helps engineers and hobbyists quickly design voltage divider circuits without manual calculations.
Formula
For two resistors in series, the output voltage is:
Where:
- Vout = Output voltage (measured in volts)
- Vin = Input voltage (measured in volts)
- R₁ = First resistor from input to output (measured in ohms)
- R₂ = Second resistor from output to ground (measured in ohms)
Voltage division ratio: Ratio = R₂ / (R₁ + R₂)
How to Use
- Enter the Input Voltage (Vin) in volts (V)
- Enter the R₁ Resistor Value in ohms (Ω) from input to output
- Enter the R₂ Resistor Value in ohms (Ω) from output to ground
- Click Calculate
- The calculator displays the Output Voltage (Vout)
Worked Example
Given:
- Input voltage (Vin) = 12 V
- R₁ = 6,800 Ω (6.8 kΩ)
- R₂ = 3,200 Ω (3.2 kΩ)
Calculation:
Vout = Vin × R₂ / (R₁ + R₂)
Vout = 12 V × 3,200 Ω / (6,800 Ω + 3,200 Ω)
Vout = 12 V × 3,200 / 10,000 = 3.84 V
Result: Output voltage is 3.84 V
Real-World Applications
- Sensor Signal Conditioning: Convert sensor output voltage to microcontroller input range
- Reference Voltage Generation: Create stable reference voltages from higher supply voltages
- Impedance Matching: Adjust signal levels between different circuit stages
- Battery Voltage Monitoring: Reduce battery voltage for safe ADC measurement
- Audio Level Adjustment: Reduce audio signal amplitude to acceptable levels
Key Definitions
- Voltage Divider: Circuit using two resistors in series to divide input voltage
- Division Ratio: Fraction of input voltage appearing at output: R₂/(R₁+R₂)
- Load Current: Current drawn by circuit connected to voltage divider output
- Loaded Voltage Divider: Voltage divider with output current flowing to a load
- Unloaded Voltage Divider: Ideal case with no output current
- Thévenin Equivalent: Voltage divider equivalent seen by load circuit
Frequently Asked Questions
What is a voltage divider?
A voltage divider is a circuit using two resistors in series to divide an input voltage into a lower output voltage. The output voltage is a fraction of the input, determined by the resistor ratio.
How do I choose resistor values for a specific output voltage?
Choose R₂ and R₁ such that R₂/(R₁+R₂) = Vout/Vin. For example, for 50% voltage division, choose equal resistor values. Keep total resistance high (>10 kΩ) to minimize current draw.
How does load current affect voltage divider output?
Load current flowing through R₂ creates additional voltage drop, reducing the output voltage. To minimize this effect, keep R₂ small (low impedance) and design for low load current, or use a buffer amplifier.
What happens if I use large resistor values?
Large resistors minimize current draw from the source, saving power. However, they increase output impedance, making the divider more susceptible to noise and load effects. Typical values are 1 kΩ to 100 kΩ.
Can I use potentiometers in voltage dividers?
Yes, variable resistors (potentiometers) can replace fixed resistors to create adjustable voltage dividers. This is useful for tuning circuits or creating adjustable power supplies.
Why do I need a buffer after a voltage divider?
A buffer amplifier isolates the voltage divider from the load, preventing load current from affecting the output voltage. This maintains stable reference voltages and allows higher output current for driving circuits.