Voltage Divider Calculator
Output voltage of a two-resistor divider, with and without a load.
What is Voltage Divider?
Two resistors in series across a supply make a voltage divider, and the output is taken across the lower one. The textbook answer is only true while nothing draws current from the tap: put a real load across R2 and the output sags, which is the most common reason a divider that calculates correctly does not behave in a circuit. Both figures are computed here, and the difference between them is the point of the page.
How it works
The unloaded output is the input scaled by R2 ÷ (R1 + R2), and the current through the stack is the input divided by the total. With a load, R2 is replaced by R2 in parallel with the load resistance before the same calculation runs, so the loaded output is always lower and the percentage sag is reported directly. A circuit diagram carries the live values, and the dissipation in each resistor is shown because the standing divider current flows whether or not the load does.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
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