Science & EngineeringFormula-based · Runs in your browser

Ohm's Law Calculator

Calculate voltage, current, resistance, and power from a selected known pair.

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Inputs

Enter the values you know. Optional fields may be left empty.

Local save controls below
Required
Required
Required

Result

Updates as valid inputs change.

Calculated locally
Use proper electrical safety procedures and rated equipment.
Power
Voltage
Current
Resistance

Saved locally, explained clearly

Drafts, calculations, scenarios, and workflow progress stay in this browser unless you export them.

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Calculation steps

Follow what happened from the selected formula to the displayed answer.

Show substituted values and intermediate working
Calculate current inputs to see the working.
  1. 1

    Formula selected

    The calculator uses the following formula or method.

    V = IR; P = VI = I²R = V²/R

  2. 2

    Values entered

    Your values are placed into the calculation.

    Enter values to see what is used in this step.

  3. 3

    Result calculated

    The formula or method produces the following result values.

    Results will appear after a successful calculation.

  4. 4

    Answer formatted

    Displayed values are rounded and formatted using each output’s configured precision.

Scenario comparison

Save working scenarios, then select two or three to compare. Formula versions and inputs remain visible.

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Recent calculations

Successful calculations are retained locally according to your privacy settings.

No local history for this calculator yet.

Data and privacy

How it works

Select which two values you know. Enter them in the same order shown in the selector.

Input query strings and outputs

Use an input name in this page’s URL as ?name=value, and join additional inputs with &. Portable shared links may instead use the compact ?ac= state parameter.

Input query strings

3
  • ?knownPair= Known values

    Choice · Required · Default: voltageResistance · Accepted values: voltageResistance, voltageCurrent, currentResistance, powerVoltage, powerCurrent, powerResistance

  • ?firstValue= First selected value

    Number · Required · Default: 12

  • ?secondValue= Second selected value

    Number · Required · Default: 6

Outputs

4
  • power Power

    Number · Primary output · Suffix: W

  • voltage Voltage

    Number · Suffix: V

  • current Current

    Number · Suffix: A

  • resistance Resistance

    Number · Suffix: Ω

Safety

This is a formula tool, not electrical installation guidance.

Sources
  • No external reference is listed for this calculator. Its formula and variable definitions are shown above.
Limitations
  • Use proper electrical safety procedures and rated equipment.
  • The model uses the stated units and idealized assumptions. Check applicability, tolerances, and safety requirements for real equipment.