Voltage Divider Calculator
Enter source voltage, top resistance, bottom resistance, and optional load resistance to estimate voltage-divider output and resistor power.
- Output voltage
- V
- Effective bottom resistance
- ohm
- Total divider resistance
- ohm
- Divider current
- A
- Top resistor power
- W
- Bottom path power
- W
Calculation details
- Calculation basis
- Boundary
Recent results
Formulas
- Effective bottom resistance = bottom resistance when load resistance is 0
- Loaded effective bottom resistance = 1 / (1 / bottom resistance + 1 / load resistance)
- Output voltage = source voltage x effective bottom resistance / (top resistance + effective bottom resistance)
- Divider current = source voltage / total divider resistance
Use this calculator
Estimate unloaded or loaded voltage-divider output from source voltage and resistor values.
Read the result
Review the calculated values with their displayed units and assumptions. The result is a planning aid for the stated inputs, not a final equipment or installation decision.
Check before final work
This is an educational component estimate. Verify resistor tolerance, wattage, source impedance, input leakage, load regulation, temperature rise, and manufacturer ratings before using a divider in real equipment.
FAQs
What does load resistance do to a voltage divider?
The load acts in parallel with the bottom resistor and usually lowers the output voltage compared with the unloaded divider.
Can this select resistor wattage?
No. It estimates power from ideal arithmetic. Choose real components using ratings, tolerance, temperature, manufacturer data, and a design review.