Watts to Amps Calculator

Estimate load current

1. Choose DC, single-phase AC or balanced three-phase AC. Enter electrical input power in watts or kilowatts; for three-phase, enter the total across all three phases.
2. Enter the voltage. For three-phase, identify whether it is measured between two lines or between a line and neutral. For AC, enter the load's known true power factor as a decimal greater than zero and no greater than one.
3. Select Calculate current, then review the amperes, input assumptions and method. Copy includes that context. Editing an input removes the old answer; changing the power unit clears power so it can be entered in the new unit.

Use the right power, voltage and power factor

Watts and amps describe different quantities, so there is no single conversion factor. A steady 60 W DC load at 12 V draws 5 A under this model, while the same power at 24 V draws 2.5 A.

Enter real electrical input power, not watt-hours, apparent power in volt-amperes or a motor's mechanical output rating. Converting a shaft-power rating would also require efficiency information that this calculator does not infer.

Single-phase current is power divided by voltage and power factor. A balanced three-phase calculation uses total power divided by the square root of three times line-to-line voltage and power factor, or by three times line-to-neutral voltage and power factor. The answer is line current, not necessarily current in a delta-connected winding.

True power factor is real power divided by apparent power. It is not efficiency and is not entered as a percentage. A phase-angle cosine can differ from true power factor when harmonics matter. Use a compatible measured or specified value; choosing one without knowing it makes the estimate unreliable.

Check the assumptions with examples

A single-phase load taking 2300 W at 230 V with a known power factor of 1 gives 10 A. At power factor 0.8, the same real power and voltage give 12.5 A. The unity example does not mean every appliance has power factor 1.

A balanced three-phase load taking 11 kW at 400 V line-to-line and power factor 0.8 gives about 19.8464 A. That is total input power and line current; do not multiply the power or the answer by three again.

For 12000 W and power factor 1, entering 400 V line-to-line gives about 17.3205 A; entering 400 V line-to-neutral gives 10 A. Those are different voltage assumptions, not two answers for the same supply. Use the voltage basis you actually know.

What this estimate does not decide

This is a current estimate, not a wire, breaker, plug, battery, generator or circuit-capacity recommendation. Installation rules, continuous-load allowances, temperature, protection and equipment instructions require a separate qualified assessment. Do not use a zero result to decide that a circuit is de-energized.

DC assumes steady voltage and current, not a reconstructed pulsed waveform. The three-phase model assumes a balanced supply and load with compatible RMS voltage/current and true power factor. It does not calculate startup or peak current, harmonic content, phase imbalance, neutral current, motor efficiency or exported power. A single-phase appliance still uses the single-phase formula even in a building with three-phase service.

Enter ungrouped numbers with a leading digit and at most six decimal places; a single dot or comma is decimal, so 1,000 means one here. Voltage must be 0.001 to 1000000 V, power factor 0.000001 to 1, and power no more than 1000000000 W or 1000000 kW. These are software limits, not safe equipment ratings. Results use up to six significant digits, with scientific notation for very small or large currents.

Your calculation

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