Voltage Divider Calculator
Calculate output voltage from a two-resistor voltage divider circuit instantly with this free electronics calculator in your browser.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the input voltage and two resistors.
- Press Calculate.
How it works
Output = input × R2 ÷ (R1 + R2). Two resistors split a voltage in proportion to their values.
Worked example
12 V, R1 1k, R2 2k. = 8 V.
Common mistakes
- Loading the divider with a low-impedance circuit, which pulls Vout below the formula value.
- Using very large resistor values that make the output noisy and current-starved.
Frequently asked questions
How does a voltage divider work?
Two series resistors split the input: Vout = Vin × R2 ÷ (R1 + R2). The output is taken across the lower resistor R2.
Why is my divider output lower than calculated?
Any load draws current in parallel with R2, lowering Vout. Keep the load impedance much higher than R2, or buffer it with an op-amp.
Does connecting a load change the output voltage?
Yes — a load draws current and pulls the output down. Voltage dividers suit high-impedance inputs (like a sensor reading), not powering devices.
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Cite this tool
Zerdly. (2026). Voltage Divider Calculator. Retrieved from https://www.zerdly.com/tools/voltage-divider-calculator/
Tip: Enter any known values to calculate the remaining results.
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