Free Electrical calculator

Ohm's law calculator

Calculate voltage, current, resistance and power from any supported pair of known electrical values.

Enter the project values

All values remain in your browser. Review the assumptions before using the result.

Your result will appear here.Calculate to see the outputs, formula and substituted working.

How the calculation works

Steady-state DC or purely resistive relationships.

Formula

V = I × R; P = V × I = I²R = V² ÷ R

Worked example

Voltage230 V

Resistance10 Ω

Expected current23 A

Expected power5,290 W

Assumptions and limitations

Assumptions

The relationship is DC or purely resistive.
Values are steady-state.

What this does not check

Does not include AC impedance, reactance, frequency or phase angle.
Does not establish conductor or equipment suitability.

Formula version: 1.0 · Last reviewed: 16 August 2026

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Engineering basis: first-principles electrical relationships using user-entered values. The page does not reproduce BS 7671 tables or establish compliance. Complete the project-specific design against the current BS 7671 information, manufacturer data and the applicable project requirements.

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