Voltage Divider Calculator
Calculate unloaded and loaded output voltage, divider current and output resistance.
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Compare unloaded and loaded divider output
Enter input voltage, the upper resistor, the lower resistor and an optional load resistance. With no load, output follows the familiar lower-resistor share of total series resistance. When a load is present, the calculator places it in parallel with the lower resistor, recalculates output sag and reports divider current, effective lower resistance and the unloaded Thevenin output resistance.
Do not treat a divider as a regulated supply
A resistor divider consumes current continuously and its output changes when the load is not large compared with its output resistance. Resistor tolerance, input variation, power dissipation, noise, source impedance and downstream input current all matter. Use buffering or a suitable regulated circuit when the load requires a stable voltage.
Frequently asked questions
Where is output measured?
Output is measured across the lower resistor R2.
How is the load included?
A positive load resistance is placed in parallel with R2 before output is calculated.
Is a voltage divider a regulated power supply?
No. Its output changes with the input, resistor tolerances and load.