Electrical calculator

Watts to Amps Calculator

Convert real power to current for DC, single-phase AC, or balanced three-phase AC circuits.

Convert real power to current

Current depends on more than wattage. DC uses watts divided by volts. For AC loads, power factor accounts for the difference between real and apparent power; balanced three-phase calculations also include the square root of three when line-to-line voltage is used.

Worked examples

A 1,200-watt DC or resistive 120-volt load draws 10 amperes in the ideal calculation. A single-phase AC load using 1,200 watts at 120 volts and 0.90 power factor draws about 11.11 amperes. A balanced three-phase 1,200-watt load at 208 volts and 0.90 power factor draws about 3.70 amperes.

Important assumptions

• The AC formulas use real power in watts, not apparent power in volt-amperes.
• The three-phase option assumes a balanced load and line-to-line voltage.
• Power factor must come from a nameplate or reliable specification; guessing it can materially change the answer.
• Starting current, harmonics, efficiency, duty cycle, conductor ampacity, and required safety margins are not calculated.

Do not size conductors, breakers, fuses, or electrical equipment solely from this conversion. Follow current codes and manufacturer instructions.

Frequently asked questions

Why does lower power factor increase amps?

The same real power requires more current when voltage and current are not perfectly aligned. Dividing by a power factor below one increases the calculated current.

What power factor should I enter?

Use the equipment nameplate or manufacturer documentation. Pure resistance is near one, while motors and electronic loads vary with design and operating condition.

Is three-phase voltage line-to-line or line-to-neutral?

This calculator’s three-phase formula uses line-to-line voltage. A line-to-neutral formulation is different, so confirm the system and measurement before calculating.

How to get a dependable result

• Use nameplate ratings or manufacturer specifications when they are available.
• Keep every input in the unit shown beside its field.
• Treat calculated values as planning estimates; real equipment, batteries, and conductors have losses, tolerances, and operating limits.

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Sources and review notes

Electrical unit relationships are consistent with the NIST SI electrical-unit guidance.

Last reviewed September 2026. Results are educational estimates and do not replace product instructions, electrical codes, engineering review, or professional advice.