Loaded Voltage Divider Calculator
Calculate output voltage with and without a load, and see how load resistance affects your divider's accuracy.
Divider Values
V
Results
Vout (no load)6.0000 V
Divider ratio0.5000
Quiescent current600 µA
Rule of thumb: RL ≥ 100.0 kΩ for <10% error
The Loading Effect Explained
An ideal voltage divider assumes no current is drawn at the output. In practice, any load connected to the output forms a parallel combination with R2, reducing the effective bottom resistance and pulling the output voltage down.
This "loading effect" is the difference between the unloaded and loaded output voltage, expressed as a percentage. It becomes significant when the load resistance is comparable to R2.
Unloaded Output
Vout = Vin × R2 / (R1 + R2)Loaded Output (R2eff = R2 ∥ RL)
Vout = Vin × R2eff / (R1 + R2eff)Key Points
- RL ≥ 10× R2 keeps loading error below ~10%
- RL ≥ 100× R2 keeps loading error below ~1%
- Lower divider resistors reduce loading but increase quiescent current
- A unity-gain op-amp buffer eliminates loading entirely
- ADC input impedance acts as a load — check the datasheet
Applications
- Battery voltage sensing with ADC
- Reference voltage generation
- Signal level shifting
- Bias networks for transistors