Use this Voltage Divider Calculator to calculate the output voltage of a resistor voltage divider. Enter the input voltage and the values of the two resistors to calculate the resulting output voltage, divider current, and power dissipation. The calculator is useful for designing and analyzing voltage divider circuits, selecting suitable resistor values, and generating a required voltage from a higher supply voltage.
Results
- Output voltage (Vout)
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- Division ratio (Vout / Vin)
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- Divider current
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- Power in R1
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- Power in R2
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- Total power
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How it works
A voltage divider is two resistors in series across a voltage source. The same current flows through both, so the input voltage is shared between them in proportion to their resistance. The output is taken across R2.
Voltage Divider Formula
Vout = Vin × R2 / (R1 + R2)
I = Vin / (R1 + R2)
PR1 = I² × R1, PR2 = I² × R2
Example: Vin = 12 V, R1 = 10 kΩ, R2 = 4.7 kΩ gives Vout = 12 × 4.7 / 14.7 ≈ 3.84 V.
Notes
- A voltage divider is suitable for reference voltages and signal levels (for example, scaling a voltage for a microcontroller ADC input). It is not a power supply: the output voltage drops as soon as a significant load current is drawn.
- Keep the load resistance at least 10 times larger than R2 for reasonable accuracy.
- Lower resistor values make the divider stiffer against loads but draw more current; higher values save power but are more sensitive to loading and noise.
