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Watts to Amps Calculator

Convert watts and amps for DC, single-phase AC, and three-phase AC circuits using voltage and, where needed, power factor.

Result

10 A

1,200 W at 120 V (DC) is about 10 A

Quick Answer

A watts to amps calculator divides power by the voltage terms for the chosen circuit. For DC, amps equal watts divided by volts, so 1,200 W at 120 V equals 10 A. AC also uses power factor, while three-phase AC adds the square root of three.

How Watts-To-Amps Conversion Works Across Circuits

A watts to amps calculator links power, voltage, and current. DC uses a direct watts divided by volts rule. Single-phase AC also uses power factor. Three-phase AC adds the square root of three when voltage is line to line. The calculator can also work in reverse. That mode finds watts or kilowatts from amps. Electricians and homeowners can use the result for an early load check. The number can also help compare nameplate data. Current does not set a breaker or wire size by itself. A final design must use the local code. The check must also cover load type, duty, wire limits, heat, and the way the cable is installed. Use the answer as a math check, not as a permit or safety approval.

The Watts, Volts And Amps Formula For Each Circuit

For reverse solving, multiply amps by the same voltage terms. Divide watts by 1,000 to show kilowatts.

  • For DC: Amps = Watts ÷ Volts.
  • For single-phase AC: Amps = Watts ÷ (Volts × Power Factor).
  • For three-phase AC: Amps = Watts ÷ (Volts × √3 × Power Factor).

Watts: real electric power.

Volts: circuit voltage.

Power factor: real power divided by apparent power for AC.

Amps: electric current.

Using A Watts To Amps Calculator In Five Clear Steps

Inputs

  • Direction: choose watts to amps or amps to kilowatts.
  • Circuit type: choose DC, single-phase AC, or three-phase AC.
  • Power: enter watts when solving for current.
  • Voltage: enter circuit voltage.
  • Power factor: enter the AC load value; DC does not use this field.

Steps

  1. Select the direction.
  2. Choose the circuit type.
  3. Enter power or current.
  4. Enter voltage and AC power factor.
  5. Read the result.

Watts To Amps Conversion Example With Full Working

A DC circuit at 1,200 W and 120 V, or a three-phase AC circuit at 12,000 W, 480 V, and 0.9 power factor.

  1. DC circuit current: divide power by voltage: 1,200 ÷ 120 = 10 A.
  2. Three-phase AC circuit denominator: 480 × 1.7320508 × 0.9 = 748.2459.
  3. Three-phase AC circuit current: divide power by that product: 12,000 ÷ 748.2459 = 16.0375 A.

The DC current is 10 A (no rounding needed) and the three-phase AC current is 16.04 A (rounded to two decimal places).

When Watts-To-Amps Math Fits Your Electrical Check

Use this math to compare loads or check nameplate data. Use the local NEC or an equal code, maker data, and a trained electrician for wire, breaker, and safety choices.

For other electrical and hardware calculations, visit the engineering calculators hub, and check the glossary for definitions of common technical terms.

Assumptions

  • Three-phase voltage is line to line.
  • The AC power factor matches the load.
  • The three-phase load is balanced.
  • Entered watts are real power.
  • Display rounding happens after the math.

Limitations

  • The result does not size a breaker or wire.
  • Motor start current is not included.
  • Harmonics and phase imbalance are not included.
  • Code load factors are not included.

In Practice

A frequent setup error is using the DC rule for an AC load. Choose the mode from the supply and nameplate, then use the result as one part of a full code check.

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Related Guides

Frequently Asked Questions About Electrical Current

Does Power Factor Change A Watts-To-Amps Result?

Power factor changes the AC current needed to deliver the same amount of real power. A lower factor means more current for the same watts and volts. Use a known load value rather than a guess for design work.

Why Does Three-Phase Math Use Square Root Three?

Balanced three-phase power uses the square root of three to link line voltage with line current. The factor comes from the phase spacing in a balanced system. Single-phase and DC circuits use different formula forms.

Can This Result Pick The Correct Circuit Breaker?

The current result cannot pick a breaker or wire size on its own. Code rules, load duty, heat, voltage drop, and equipment data also matter. Final choices must follow the local code and the maker instructions.

How Do I Convert Amps Back Into Kilowatts?

Multiply amps by voltage and the needed AC factors to find real power in watts. Divide that watt result by 1,000 to show kilowatts. Use the same circuit mode and power factor used for the current check.

Sources

Last updated: . Reviewed for accuracy against the formula shown above.