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Amps to Kilowatts Calculator

Convert electrical current (amps) to power in kilowatts for DC, single-phase AC, and three-phase AC circuits

What this tool does

Convert electrical current (amps) to power in kilowatts for DC, single-phase AC, and three-phase AC circuits. You fill in these fields: Circuit type, Current, and Voltage. Some fields appear only for certain choices. It shows power, power in watts, and apparent power.

Inputs

  • Circuit type: Switch between: DC, AC single-phase, AC three-phase. Three-phase uses the line-to-line voltage.
  • Current (A): A number. Must be at most 10,000,000. Must be greater than 0.
  • Voltage (V): A number. Must be at most 10,000,000. Must be greater than 0. For three-phase, enter the line-to-line voltage.
  • Power factor: A number. Accepts 0.01 to 1. Shown only when "Circuit type" is not DC. Enter the equipment's real power factor from its nameplate or data sheet. Use 1 only for purely resistive loads such as heaters.

How to use

  1. Choose DC, AC single-phase, or AC three-phase for "Circuit type".
  2. Enter the current in A.
  3. Enter the voltage in V.
  4. If "Circuit type" is not DC, enter the power factor.
  5. Read the result: power, power in watts, and apparent power. It appears once every required field has a valid value.

Worked examples

Example 1. Inputs:

  • Circuit type: DC
  • Current: 12 A
  • Voltage: 120 V

Results:

  • Power: 1.44 kW
  • Power in watts: 1,440 W

How this is worked out: DC: P = V x I = 120 x 12 = 1440 W = 1.44 kW. No power factor applies.

Example 2. Inputs:

  • Circuit type: AC single-phase
  • Current: 20 A
  • Voltage: 240 V
  • Power factor: 0.9

Results:

  • Power: 4.32 kW
  • Power in watts: 4,320 W
  • Apparent power: 4.8 kVA

How this is worked out: Single-phase AC: P = V x I x PF = 240 x 20 x 0.9 = 4320 W = 4.32 kW. Apparent power S = V x I = 4800 VA = 4.8 kVA.

Example 3. Inputs:

  • Circuit type: AC three-phase
  • Current: 100 A
  • Voltage: 480 V
  • Power factor: 0.8

Results:

  • Power: 66.510751 kW
  • Power in watts: 66,510.751011 W
  • Apparent power: 83.138439 kVA

How this is worked out: Three-phase AC, line-to-line volts: P = sqrt(3) x V x I x PF / 1000 = 1.7320508 x 480 x 100 x 0.8 / 1000 = 1.7320508 x 38400 / 1000 = 66.5108 kW. S = 1.7320508 x 48000 / 1000 = 83.1384 kVA.

Example 4. Inputs:

  • Circuit type: AC three-phase
  • Current: 10 A
  • Voltage: 208 V
  • Power factor: 1

Results:

  • Power: 3.602666 kW
  • Power in watts: 3,602.66568 W
  • Apparent power: 3.602666 kVA

How this is worked out: Three-phase AC at unity power factor, line-to-line volts: P = S = sqrt(3) x V x I = 1.7320508 x 208 x 10 = 1.7320508 x 2080 = 3602.666 W = 3.602666 kW, and kVA equals kW because PF = 1.

Limitations

  • Assumes sinusoidal voltage and current. Loads with heavy harmonic distortion need a power-quality analysis.
  • Three-phase results assume a balanced load, with equal current in all three lines.
  • Wire and equipment losses are not included; the result is the power at the load for the figures you enter.

FAQs

Q: What power factor should I enter?
A: Use the value on the equipment's nameplate or data sheet. The calculator has no default for it, because the right value depends on the load. A purely resistive load such as a heater has a power factor of 1.
Q: Which voltage do I enter for three-phase?
A: The line-to-line voltage, measured between two of the three conductors, together with the current in one line. The calculator multiplies by the square root of 3 for you.
Q: Why is there no power factor for DC?
A: In a DC circuit voltage and current are always in phase, so power is simply volts times amps. The power factor field only appears for the AC choices.
Q: What is the difference between kW and kVA?
A: Kilowatts are the real power doing work. Kilovolt-amperes are the apparent power, volts times amps (times the square root of 3 for three-phase). Kilowatts equal kilovolt-amperes times the power factor.
Q: Can I use it for a 240 V household circuit?
A: Yes. Choose AC single-phase, enter 240 V and the load's current and power factor.

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