Voltage Divider Calculator — Free Engineering Tool

Electrical lab bench with calculator, multimeter, oscilloscope, and low-voltage test circuit used to verify Voltage Divider Calculator results.
Calculate the nominal result, then verify assumptions, limits, and real behavior with appropriate measurements.
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Voltage Divider Calculator input-to-result overview.
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Formula and unit relationship.
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Worked-example calculation path.
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Input and assumption checklist.
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Nominal result and interpretation.
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Tolerance and worst-case verification.
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Editable-circuit and related-tool next step.
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Safety, model, and professional-review boundary.

Voltage Divider Calculator formula and engineering interpretation

A two-resistor divider produces a fraction of its input. The nominal formula is simple, but the load connected to the output appears in parallel with the lower resistor and can materially change the answer.

Formula

Vout = Vin × R2/(R1 + R2). Loaded: replace R2 with (R2 × Rload)/(R2 + Rload).

Worked example

A 12 V divider with two 10 kΩ resistors gives 6 V unloaded. Connecting a 10 kΩ load makes the effective lower leg 5 kΩ and the output becomes 4 V.

How to use the result in a real design

Balance source loading against output impedance. Lower resistor values make the divider stiffer but waste more current. Higher values save power but become more sensitive to leakage, noise, sampling capacitors and meter input resistance.

What the result does not prove

The nominal result excludes resistor tolerance, supply variation, temperature coefficient, input leakage, transient response and noise. A divider is not a regulated power supply.

Verification workflow

  1. Confirm every input and unit from a source document or measurement.
  2. Calculate the nominal result and record the assumptions.
  3. Repeat with credible minimum and maximum input values.
  4. Compare component ratings, temperature and abnormal conditions.
  5. Open an editable circuit, run supported checks, and obtain professional review where safety depends on the answer.

Related design tools

Continue with the voltage drop calculator, wire size calculator, supported-model circuit simulator, or open the browser editor.

Review note: Equations and example arithmetic were reviewed on 2026-07-30. Results are planning aids, not certification or installation instructions.