ELECTRONICS · CALCULATOR

Voltage divider calculator

Free voltage divider calculator: get unloaded output from voltage, upper resistance and lower resistance. The formula is shown; verify against the NEC.

Written by Chameera Sampath · Not yet reviewed by a licensed electrician. See the methodology.

US (NEC) only · NFPA 70 / NEC — locally adopted editionDefaults are US values. Verify the locally adopted NEC edition and project data.Official reference ↗

Project inputs

Measurements

Voltage

Upper resistance

Lower resistance

Updates as inputs change. Unit changes preserve the same physical values.

THE MATH BEHIND THE ANSWER

Method & assumptions

Vout = Vin × R2 / (R1 + R2)

Load resistance changes the output.

Results do not check every aspect of an electrical installation. The calculators follow US (NEC) practice only; a regional preset changes defaults such as voltage and units, and no result certifies NEC compliance.

Sources and validation →

Worked example

Voltage: 12 V · Upper resistance: 10,000 Ω · Lower resistance: 10,000 Ω

Unloaded output: 6 V

This example uses the stated inputs; results for the entered values appear above.

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