Resistor Divider Calculator
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Classic two-resistor voltage divider for reference and sensor scaling.
Divider
Output voltage
2.5 V
Divider ratio: 50%
- Divider current
- 0.25 mA
- Vout / Vin
- 0.5
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Voltage dividers
Two resistors in series split input voltage proportionally. Output at the junction: Vout = Vin × R2 ÷ (R1 + R2). Load current drawn from the tap lowers Vout — this formula assumes negligible load current.
Dividers set reference voltages, scale sensors, and bias transistors. For stable output under load, use a buffer op-amp or size resistors small enough that load current is negligible (watch power dissipation).
Example: 5 V input, R1 = 10 kΩ, R2 = 10 kΩ → Vout = 2.5 V. Current through divider = 5 V ÷ 20 kΩ = 0.25 mA.
Common questions
Why does my measured voltage differ?
Multimeter loading, supply tolerance, and resistor tolerance affect readings. Heavy load on Vout pulls voltage down.
Can I use this for AC?
Same formula for resistive AC at an instant, using RMS values. Capacitive dividers need different math.